diff --git a/src/lib/WebAuthn/Attestation/AttestationObject.php b/src/lib/WebAuthn/Attestation/AttestationObject.php
new file mode 100644
index 0000000..65151ea
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/AttestationObject.php
@@ -0,0 +1,179 @@
+<?php
+
+namespace lbuchs\WebAuthn\Attestation;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\CBOR\CborDecoder;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+/**
+ * @author Lukas Buchs
+ * @license https://github.com/lbuchs/WebAuthn/blob/master/LICENSE MIT
+ */
+class AttestationObject {
+    private $_authenticatorData;
+    private $_attestationFormat;
+    private $_attestationFormatName;
+
+    public function __construct($binary , $allowedFormats) {
+        $enc = CborDecoder::decode($binary);
+        // validation
+        if (!\is_array($enc) || !\array_key_exists('fmt', $enc) || !is_string($enc['fmt'])) {
+            throw new WebAuthnException('invalid attestation format', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('attStmt', $enc) || !\is_array($enc['attStmt'])) {
+            throw new WebAuthnException('invalid attestation format (attStmt not available)', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('authData', $enc) || !\is_object($enc['authData']) || !($enc['authData'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('invalid attestation format (authData not available)', WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_authenticatorData = new AuthenticatorData($enc['authData']->getBinaryString());
+        $this->_attestationFormatName = $enc['fmt'];
+
+        // Format ok?
+        if (!in_array($this->_attestationFormatName, $allowedFormats)) {
+            throw new WebAuthnException('invalid atttestation format: ' . $this->_attestationFormatName, WebAuthnException::INVALID_DATA);
+        }
+
+
+        switch ($this->_attestationFormatName) {
+            case 'android-key': $this->_attestationFormat = new Format\AndroidKey($enc, $this->_authenticatorData); break;
+            case 'android-safetynet': $this->_attestationFormat = new Format\AndroidSafetyNet($enc, $this->_authenticatorData); break;
+            case 'apple': $this->_attestationFormat = new Format\Apple($enc, $this->_authenticatorData); break;
+            case 'fido-u2f': $this->_attestationFormat = new Format\U2f($enc, $this->_authenticatorData); break;
+            case 'none': $this->_attestationFormat = new Format\None($enc, $this->_authenticatorData); break;
+            case 'packed': $this->_attestationFormat = new Format\Packed($enc, $this->_authenticatorData); break;
+            case 'tpm': $this->_attestationFormat = new Format\Tpm($enc, $this->_authenticatorData); break;
+            default: throw new WebAuthnException('invalid attestation format: ' . $enc['fmt'], WebAuthnException::INVALID_DATA);
+        }
+    }
+
+    /**
+     * returns the attestation format name
+     * @return string
+     */
+    public function getAttestationFormatName() {
+        return $this->_attestationFormatName;
+    }
+
+    /**
+     * returns the attestation format class
+     * @return Format\FormatBase
+     */
+    public function getAttestationFormat() {
+        return $this->_attestationFormat;
+    }
+
+    /**
+     * returns the attestation public key in PEM format
+     * @return AuthenticatorData
+     */
+    public function getAuthenticatorData() {
+        return $this->_authenticatorData;
+    }
+
+    /**
+     * returns the certificate chain as PEM
+     * @return string|null
+     */
+    public function getCertificateChain() {
+        return $this->_attestationFormat->getCertificateChain();
+    }
+
+    /**
+     * return the certificate issuer as string
+     * @return string
+     */
+    public function getCertificateIssuer() {
+        $pem = $this->getCertificatePem();
+        $issuer = '';
+        if ($pem) {
+            $certInfo = \openssl_x509_parse($pem);
+            if (\is_array($certInfo) && \array_key_exists('issuer', $certInfo) && \is_array($certInfo['issuer'])) {
+
+                $cn = $certInfo['issuer']['CN'] ?? '';
+                $o = $certInfo['issuer']['O'] ?? '';
+                $ou = $certInfo['issuer']['OU'] ?? '';
+
+                if ($cn) {
+                    $issuer .= $cn;
+                }
+                if ($issuer && ($o || $ou)) {
+                    $issuer .= ' (' . trim($o . ' ' . $ou) . ')';
+                } else {
+                    $issuer .= trim($o . ' ' . $ou);
+                }
+            }
+        }
+
+        return $issuer;
+    }
+
+    /**
+     * return the certificate subject as string
+     * @return string
+     */
+    public function getCertificateSubject() {
+        $pem = $this->getCertificatePem();
+        $subject = '';
+        if ($pem) {
+            $certInfo = \openssl_x509_parse($pem);
+            if (\is_array($certInfo) && \array_key_exists('subject', $certInfo) && \is_array($certInfo['subject'])) {
+
+                $cn = $certInfo['subject']['CN'] ?? '';
+                $o = $certInfo['subject']['O'] ?? '';
+                $ou = $certInfo['subject']['OU'] ?? '';
+
+                if ($cn) {
+                    $subject .= $cn;
+                }
+                if ($subject && ($o || $ou)) {
+                    $subject .= ' (' . trim($o . ' ' . $ou) . ')';
+                } else {
+                    $subject .= trim($o . ' ' . $ou);
+                }
+            }
+        }
+
+        return $subject;
+    }
+
+    /**
+     * returns the key certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        return $this->_attestationFormat->getCertificatePem();
+    }
+
+    /**
+     * checks validity of the signature
+     * @param string $clientDataHash
+     * @return bool
+     * @throws WebAuthnException
+     */
+    public function validateAttestation($clientDataHash) {
+        return $this->_attestationFormat->validateAttestation($clientDataHash);
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        return $this->_attestationFormat->validateRootCertificate($rootCas);
+    }
+
+    /**
+     * checks if the RpId-Hash is valid
+     * @param string$rpIdHash
+     * @return bool
+     */
+    public function validateRpIdHash($rpIdHash) {
+        return $rpIdHash === $this->_authenticatorData->getRpIdHash();
+    }
+}
diff --git a/src/lib/WebAuthn/Attestation/AuthenticatorData.php b/src/lib/WebAuthn/Attestation/AuthenticatorData.php
new file mode 100644
index 0000000..0a9eec8
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/AuthenticatorData.php
@@ -0,0 +1,481 @@
+<?php
+
+namespace lbuchs\WebAuthn\Attestation;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\CBOR\CborDecoder;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+/**
+ * @author Lukas Buchs
+ * @license https://github.com/lbuchs/WebAuthn/blob/master/LICENSE MIT
+ */
+class AuthenticatorData {
+    protected $_binary;
+    protected $_rpIdHash;
+    protected $_flags;
+    protected $_signCount;
+    protected $_attestedCredentialData;
+    protected $_extensionData;
+
+
+
+    // Cose encoded keys
+    private static $_COSE_KTY = 1;
+    private static $_COSE_ALG = 3;
+
+    // Cose curve
+    private static $_COSE_CRV = -1;
+    private static $_COSE_X = -2;
+    private static $_COSE_Y = -3;
+
+    // Cose RSA PS256
+    private static $_COSE_N = -1;
+    private static $_COSE_E = -2;
+
+    // EC2 key type
+    private static $_EC2_TYPE = 2;
+    private static $_EC2_ES256 = -7;
+    private static $_EC2_P256 = 1;
+
+    // RSA key type
+    private static $_RSA_TYPE = 3;
+    private static $_RSA_RS256 = -257;
+
+    // OKP key type
+    private static $_OKP_TYPE = 1;
+    private static $_OKP_ED25519 = 6;
+    private static $_OKP_EDDSA = -8;
+
+    /**
+     * Parsing the authenticatorData binary.
+     * @param string $binary
+     * @throws WebAuthnException
+     */
+    public function __construct($binary) {
+        if (!\is_string($binary) || \strlen($binary) < 37) {
+            throw new WebAuthnException('Invalid authenticatorData input', WebAuthnException::INVALID_DATA);
+        }
+        $this->_binary = $binary;
+
+        // Read infos from binary
+        // https://www.w3.org/TR/webauthn/#sec-authenticator-data
+
+        // RP ID
+        $this->_rpIdHash = \substr($binary, 0, 32);
+
+        // flags (1 byte)
+        $flags = \unpack('Cflags', \substr($binary, 32, 1))['flags'];
+        $this->_flags = $this->_readFlags($flags);
+
+        // signature counter: 32-bit unsigned big-endian integer.
+        $this->_signCount = \unpack('Nsigncount', \substr($binary, 33, 4))['signcount'];
+
+        $offset = 37;
+        // https://www.w3.org/TR/webauthn/#sec-attested-credential-data
+        if ($this->_flags->attestedDataIncluded) {
+            $this->_attestedCredentialData = $this->_readAttestData($binary, $offset);
+        }
+
+        if ($this->_flags->extensionDataIncluded) {
+            $this->_readExtensionData(\substr($binary, $offset));
+        }
+    }
+
+    /**
+     * Authenticator Attestation Globally Unique Identifier, a unique number
+     * that identifies the model of the authenticator (not the specific instance
+     * of the authenticator)
+     * The aaguid may be 0 if the user is using a old u2f device and/or if
+     * the browser is using the fido-u2f format.
+     * @return string
+     * @throws WebAuthnException
+     */
+    public function getAAGUID() {
+        if (!($this->_attestedCredentialData instanceof \stdClass)) {
+            throw  new WebAuthnException('credential data not included in authenticator data', WebAuthnException::INVALID_DATA);
+        }
+        return $this->_attestedCredentialData->aaguid;
+    }
+
+    /**
+     * returns the authenticatorData as binary
+     * @return string
+     */
+    public function getBinary() {
+        return $this->_binary;
+    }
+
+    /**
+     * returns the credentialId
+     * @return string
+     * @throws WebAuthnException
+     */
+    public function getCredentialId() {
+        if (!($this->_attestedCredentialData instanceof \stdClass)) {
+            throw  new WebAuthnException('credential id not included in authenticator data', WebAuthnException::INVALID_DATA);
+        }
+        return $this->_attestedCredentialData->credentialId;
+    }
+
+    /**
+     * returns the public key in PEM format
+     * @return string
+     */
+    public function getPublicKeyPem() {
+        if (!($this->_attestedCredentialData instanceof \stdClass) || !isset($this->_attestedCredentialData->credentialPublicKey)) {
+            throw  new WebAuthnException('credential data not included in authenticator data', WebAuthnException::INVALID_DATA);
+        }
+        
+        $der = null;
+        switch ($this->_attestedCredentialData->credentialPublicKey->kty ?? null) {
+            case self::$_EC2_TYPE: $der = $this->_getEc2Der(); break;
+            case self::$_RSA_TYPE: $der = $this->_getRsaDer(); break;
+            case self::$_OKP_TYPE: $der = $this->_getOkpDer(); break;
+            default: throw new WebAuthnException('invalid key type', WebAuthnException::INVALID_DATA);
+        }
+
+        $pem = '-----BEGIN PUBLIC KEY-----' . "\n";
+        $pem .= \chunk_split(\base64_encode($der), 64, "\n");
+        $pem .= '-----END PUBLIC KEY-----' . "\n";
+        return $pem;
+    }
+
+    /**
+     * returns the public key in U2F format
+     * @return string
+     * @throws WebAuthnException
+     */
+    public function getPublicKeyU2F() {
+        if (!($this->_attestedCredentialData instanceof \stdClass) || !isset($this->_attestedCredentialData->credentialPublicKey)) {
+            throw  new WebAuthnException('credential data not included in authenticator data', WebAuthnException::INVALID_DATA);
+        }
+        if (($this->_attestedCredentialData->credentialPublicKey->kty ?? null) !== self::$_EC2_TYPE) {
+            throw new WebAuthnException('signature algorithm not ES256', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+        return "\x04" . // ECC uncompressed
+                $this->_attestedCredentialData->credentialPublicKey->x .
+                $this->_attestedCredentialData->credentialPublicKey->y;
+    }
+
+    /**
+     * returns the SHA256 hash of the relying party id (=hostname)
+     * @return string
+     */
+    public function getRpIdHash() {
+        return $this->_rpIdHash;
+    }
+
+    /**
+     * returns the sign counter
+     * @return int
+     */
+    public function getSignCount() {
+        return $this->_signCount;
+    }
+
+    /**
+     * returns true if the user is present
+     * @return boolean
+     */
+    public function getUserPresent() {
+        return $this->_flags->userPresent;
+    }
+
+    /**
+     * returns true if the user is verified
+     * @return boolean
+     */
+    public function getUserVerified() {
+        return $this->_flags->userVerified;
+    }
+
+    // -----------------------------------------------
+    // PRIVATE
+    // -----------------------------------------------
+
+    /**
+     * Returns DER encoded EC2 key
+     * @return string
+     */
+    private function _getEc2Der() {
+        return $this->_der_sequence(
+            $this->_der_sequence(
+                $this->_der_oid("\x2A\x86\x48\xCE\x3D\x02\x01") . // OID 1.2.840.10045.2.1 ecPublicKey
+                $this->_der_oid("\x2A\x86\x48\xCE\x3D\x03\x01\x07")  // 1.2.840.10045.3.1.7 prime256v1
+            ) .
+            $this->_der_bitString($this->getPublicKeyU2F())
+        );
+    }
+
+    /**
+     * Returns DER encoded EdDSA key
+     * @return string
+     */
+    private function _getOkpDer() {
+        return $this->_der_sequence(
+            $this->_der_sequence(
+                $this->_der_oid("\x2B\x65\x70") // OID 1.3.101.112 curveEd25519 (EdDSA 25519 signature algorithm)
+            ) .
+            $this->_der_bitString($this->_attestedCredentialData->credentialPublicKey->x)
+        );
+    }
+
+    /**
+     * Returns DER encoded RSA key
+     * @return string
+     */
+    private function _getRsaDer() {
+        return $this->_der_sequence(
+            $this->_der_sequence(
+                $this->_der_oid("\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01") . // OID 1.2.840.113549.1.1.1 rsaEncryption
+                $this->_der_nullValue()
+            ) .
+            $this->_der_bitString(
+                $this->_der_sequence(
+                    $this->_der_unsignedInteger($this->_attestedCredentialData->credentialPublicKey->n) .
+                    $this->_der_unsignedInteger($this->_attestedCredentialData->credentialPublicKey->e)
+                )
+            )
+        );
+    }
+
+    /**
+     * reads the flags from flag byte
+     * @param string $binFlag
+     * @return \stdClass
+     */
+    private function _readFlags($binFlag) {
+        $flags = new \stdClass();
+
+        $flags->bit_0 = !!($binFlag & 1);
+        $flags->bit_1 = !!($binFlag & 2);
+        $flags->bit_2 = !!($binFlag & 4);
+        $flags->bit_3 = !!($binFlag & 8);
+        $flags->bit_4 = !!($binFlag & 16);
+        $flags->bit_5 = !!($binFlag & 32);
+        $flags->bit_6 = !!($binFlag & 64);
+        $flags->bit_7 = !!($binFlag & 128);
+
+        // named flags
+        $flags->userPresent = $flags->bit_0;
+        $flags->userVerified = $flags->bit_2;
+        $flags->attestedDataIncluded = $flags->bit_6;
+        $flags->extensionDataIncluded = $flags->bit_7;
+        return $flags;
+    }
+
+    /**
+     * read attested data
+     * @param string $binary
+     * @param int $endOffset
+     * @return \stdClass
+     * @throws WebAuthnException
+     */
+    private function _readAttestData($binary, &$endOffset) {
+        $attestedCData = new \stdClass();
+        if (\strlen($binary) <= 55) {
+            throw new WebAuthnException('Attested data should be present but is missing', WebAuthnException::INVALID_DATA);
+        }
+
+        // The AAGUID of the authenticator
+        $attestedCData->aaguid = \substr($binary, 37, 16);
+
+        //Byte length L of Credential ID, 16-bit unsigned big-endian integer.
+        $length = \unpack('nlength', \substr($binary, 53, 2))['length'];
+        $attestedCData->credentialId = \substr($binary, 55, $length);
+
+        // set end offset
+        $endOffset = 55 + $length;
+
+        // extract public key
+        $attestedCData->credentialPublicKey = $this->_readCredentialPublicKey($binary, 55 + $length, $endOffset);
+
+        return $attestedCData;
+    }
+
+    /**
+     * reads COSE key-encoded elliptic curve public key in EC2 format
+     * @param string $binary
+     * @param int $endOffset
+     * @return \stdClass
+     * @throws WebAuthnException
+     */
+    private function _readCredentialPublicKey($binary, $offset, &$endOffset) {
+        $enc = CborDecoder::decodeInPlace($binary, $offset, $endOffset);
+
+        // COSE key-encoded elliptic curve public key in EC2 format
+        $credPKey = new \stdClass();
+        $credPKey->kty = $enc[self::$_COSE_KTY];
+        $credPKey->alg = $enc[self::$_COSE_ALG];
+
+        switch ($credPKey->alg) {
+            case self::$_EC2_ES256: $this->_readCredentialPublicKeyES256($credPKey, $enc); break;
+            case self::$_RSA_RS256: $this->_readCredentialPublicKeyRS256($credPKey, $enc); break;
+            case self::$_OKP_EDDSA: $this->_readCredentialPublicKeyEDDSA($credPKey, $enc); break;
+        }
+
+        return $credPKey;
+    }
+
+    /**
+     * extract EDDSA informations from cose
+     * @param \stdClass $credPKey
+     * @param \stdClass $enc
+     * @throws WebAuthnException
+     */
+    private function _readCredentialPublicKeyEDDSA(&$credPKey, $enc) {
+        $credPKey->crv = $enc[self::$_COSE_CRV];
+        $credPKey->x   = $enc[self::$_COSE_X] instanceof ByteBuffer ? $enc[self::$_COSE_X]->getBinaryString() : null;
+        unset ($enc);
+
+        // Validation
+        if ($credPKey->kty !== self::$_OKP_TYPE) {
+            throw new WebAuthnException('public key not in OKP format', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if ($credPKey->alg !== self::$_OKP_EDDSA) {
+            throw new WebAuthnException('signature algorithm not EdDSA', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if ($credPKey->crv !== self::$_OKP_ED25519) {
+            throw new WebAuthnException('curve not Ed25519', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if (\strlen($credPKey->x) !== 32) {
+            throw new WebAuthnException('Invalid X-coordinate', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+    }
+
+    /**
+     * extract ES256 informations from cose
+     * @param \stdClass $credPKey
+     * @param \stdClass $enc
+     * @throws WebAuthnException
+     */
+    private function _readCredentialPublicKeyES256(&$credPKey, $enc) {
+        $credPKey->crv = $enc[self::$_COSE_CRV];
+        $credPKey->x   = $enc[self::$_COSE_X] instanceof ByteBuffer ? $enc[self::$_COSE_X]->getBinaryString() : null;
+        $credPKey->y   = $enc[self::$_COSE_Y] instanceof ByteBuffer ? $enc[self::$_COSE_Y]->getBinaryString() : null;
+        unset ($enc);
+
+        // Validation
+        if ($credPKey->kty !== self::$_EC2_TYPE) {
+            throw new WebAuthnException('public key not in EC2 format', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if ($credPKey->alg !== self::$_EC2_ES256) {
+            throw new WebAuthnException('signature algorithm not ES256', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if ($credPKey->crv !== self::$_EC2_P256) {
+            throw new WebAuthnException('curve not P-256', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if (\strlen($credPKey->x) !== 32) {
+            throw new WebAuthnException('Invalid X-coordinate', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if (\strlen($credPKey->y) !== 32) {
+            throw new WebAuthnException('Invalid Y-coordinate', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+    }
+
+    /**
+     * extract RS256 informations from COSE
+     * @param \stdClass $credPKey
+     * @param \stdClass $enc
+     * @throws WebAuthnException
+     */
+    private function _readCredentialPublicKeyRS256(&$credPKey, $enc) {
+        $credPKey->n = $enc[self::$_COSE_N] instanceof ByteBuffer ? $enc[self::$_COSE_N]->getBinaryString() : null;
+        $credPKey->e = $enc[self::$_COSE_E] instanceof ByteBuffer ? $enc[self::$_COSE_E]->getBinaryString() : null;
+        unset ($enc);
+
+        // Validation
+        if ($credPKey->kty !== self::$_RSA_TYPE) {
+            throw new WebAuthnException('public key not in RSA format', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if ($credPKey->alg !== self::$_RSA_RS256) {
+            throw new WebAuthnException('signature algorithm not ES256', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if (\strlen($credPKey->n) !== 256) {
+            throw new WebAuthnException('Invalid RSA modulus', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        if (\strlen($credPKey->e) !== 3) {
+            throw new WebAuthnException('Invalid RSA public exponent', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+    }
+
+    /**
+     * reads cbor encoded extension data.
+     * @param string $binary
+     * @return array
+     * @throws WebAuthnException
+     */
+    private function _readExtensionData($binary) {
+        $ext = CborDecoder::decode($binary);
+        if (!\is_array($ext)) {
+            throw new WebAuthnException('invalid extension data', WebAuthnException::INVALID_DATA);
+        }
+
+        return $ext;
+    }
+
+
+    // ---------------
+    // DER functions
+    // ---------------
+
+    private function _der_length($len) {
+        if ($len < 128) {
+            return \chr($len);
+        }
+        $lenBytes = '';
+        while ($len > 0) {
+            $lenBytes = \chr($len % 256) . $lenBytes;
+            $len = \intdiv($len, 256);
+        }
+        return \chr(0x80 | \strlen($lenBytes)) . $lenBytes;
+    }
+
+    private function _der_sequence($contents) {
+        return "\x30" . $this->_der_length(\strlen($contents)) . $contents;
+    }
+
+    private function _der_oid($encoded) {
+        return "\x06" . $this->_der_length(\strlen($encoded)) . $encoded;
+    }
+
+    private function _der_bitString($bytes) {
+        return "\x03" . $this->_der_length(\strlen($bytes) + 1) . "\x00" . $bytes;
+    }
+
+    private function _der_nullValue() {
+        return "\x05\x00";
+    }
+
+    private function _der_unsignedInteger($bytes) {
+        $len = \strlen($bytes);
+
+        // Remove leading zero bytes
+        for ($i = 0; $i < ($len - 1); $i++) {
+            if (\ord($bytes[$i]) !== 0) {
+                break;
+            }
+        }
+        if ($i !== 0) {
+            $bytes = \substr($bytes, $i);
+        }
+
+        // If most significant bit is set, prefix with another zero to prevent it being seen as negative number
+        if ((\ord($bytes[0]) & 0x80) !== 0) {
+            $bytes = "\x00" . $bytes;
+        }
+
+        return "\x02" . $this->_der_length(\strlen($bytes)) . $bytes;
+    }
+}
diff --git a/src/lib/WebAuthn/Attestation/Format/AndroidKey.php b/src/lib/WebAuthn/Attestation/Format/AndroidKey.php
new file mode 100644
index 0000000..4581272
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/AndroidKey.php
@@ -0,0 +1,96 @@
+<?php
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class AndroidKey extends FormatBase {
+    private $_alg;
+    private $_signature;
+    private $_x5c;
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check u2f data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+        if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
+            throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) < 1) {
+            throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
+            throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_alg = $attStmt['alg'];
+        $this->_signature = $attStmt['sig']->getBinaryString();
+        $this->_x5c = $attStmt['x5c'][0]->getBinaryString();
+
+        if (count($attStmt['x5c']) > 1) {
+            for ($i=1; $i<count($attStmt['x5c']); $i++) {
+                $this->_x5c_chain[] = $attStmt['x5c'][$i]->getBinaryString();
+            }
+            unset ($i);
+        }
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        return $this->_createCertificatePem($this->_x5c);
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        if ($publicKey === false) {
+            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
+        // using the attestation public key in attestnCert with the algorithm specified in alg.
+        $dataToVerify = $this->_authenticatorData->getBinary();
+        $dataToVerify .= $clientDataHash;
+
+        $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
+
+        // check certificate
+        return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+}
+
diff --git a/src/lib/WebAuthn/Attestation/Format/AndroidSafetyNet.php b/src/lib/WebAuthn/Attestation/Format/AndroidSafetyNet.php
new file mode 100644
index 0000000..ba0db52
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/AndroidSafetyNet.php
@@ -0,0 +1,152 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class AndroidSafetyNet extends FormatBase {
+    private $_signature;
+    private $_signedValue;
+    private $_x5c;
+    private $_payload;
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+        if (!\array_key_exists('ver', $attStmt) || !$attStmt['ver']) {
+            throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('response', $attStmt) || !($attStmt['response'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
+        }
+
+        $response = $attStmt['response']->getBinaryString();
+
+        // Response is a JWS [RFC7515] object in Compact Serialization.
+        // JWSs have three segments separated by two period ('.') characters
+        $parts = \explode('.', $response);
+        unset ($response);
+        if (\count($parts) !== 3) {
+            throw new WebAuthnException('invalid JWS data', WebAuthnException::INVALID_DATA);
+        }
+
+        $header = $this->_base64url_decode($parts[0]);
+        $payload = $this->_base64url_decode($parts[1]);
+        $this->_signature = $this->_base64url_decode($parts[2]);
+        $this->_signedValue = $parts[0] . '.' . $parts[1];
+        unset ($parts);
+
+        $header = \json_decode($header);
+        $payload = \json_decode($payload);
+
+        if (!($header instanceof \stdClass)) {
+            throw new WebAuthnException('invalid JWS header', WebAuthnException::INVALID_DATA);
+        }
+        if (!($payload instanceof \stdClass)) {
+            throw new WebAuthnException('invalid JWS payload', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!isset($header->x5c) || !is_array($header->x5c) || count($header->x5c) === 0) {
+            throw new WebAuthnException('No X.509 signature in JWS Header', WebAuthnException::INVALID_DATA);
+        }
+
+        // algorithm
+        if (!\in_array($header->alg, array('RS256', 'ES256'))) {
+            throw new WebAuthnException('invalid JWS algorithm ' . $header->alg, WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_x5c = \base64_decode($header->x5c[0]);
+        $this->_payload = $payload;
+
+        if (count($header->x5c) > 1) {
+            for ($i=1; $i<count($header->x5c); $i++) {
+                $this->_x5c_chain[] = \base64_decode($header->x5c[$i]);
+            }
+            unset ($i);
+        }
+    }
+
+    /**
+     * ctsProfileMatch: A stricter verdict of device integrity.
+     * If the value of ctsProfileMatch is true, then the profile of the device running your app matches
+     * the profile of a device that has passed Android compatibility testing and
+     * has been approved as a Google-certified Android device.
+     * @return bool
+     */
+    public function ctsProfileMatch() {
+        return isset($this->_payload->ctsProfileMatch) ? !!$this->_payload->ctsProfileMatch : false;
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        return $this->_createCertificatePem($this->_x5c);
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        // Verify that the nonce in the response is identical to the Base64 encoding
+        // of the SHA-256 hash of the concatenation of authenticatorData and clientDataHash.
+        if (empty($this->_payload->nonce) || $this->_payload->nonce !== \base64_encode(\hash('SHA256', $this->_authenticatorData->getBinary() . $clientDataHash, true))) {
+            throw new WebAuthnException('invalid nonce in JWS payload', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify that attestationCert is issued to the hostname "attest.android.com"
+        $certInfo = \openssl_x509_parse($this->getCertificatePem());
+        if (!\is_array($certInfo) || ($certInfo['subject']['CN'] ?? '') !== 'attest.android.com') {
+            throw new WebAuthnException('invalid certificate CN in JWS (' . ($certInfo['subject']['CN'] ?? '-'). ')', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify that the basicIntegrity attribute in the payload of response is true.
+        if (empty($this->_payload->basicIntegrity)) {
+            throw new WebAuthnException('invalid basicIntegrity in payload', WebAuthnException::INVALID_DATA);
+        }
+
+        // check certificate
+        return \openssl_verify($this->_signedValue, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 1;
+    }
+
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+
+
+    /**
+     * decode base64 url
+     * @param string $data
+     * @return string
+     */
+    private function _base64url_decode($data) {
+        return \base64_decode(\strtr($data, '-_', '+/') . \str_repeat('=', 3 - (3 + \strlen($data)) % 4));
+    }
+}
+
diff --git a/src/lib/WebAuthn/Attestation/Format/Apple.php b/src/lib/WebAuthn/Attestation/Format/Apple.php
new file mode 100644
index 0000000..e4f38e0
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/Apple.php
@@ -0,0 +1,139 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class Apple extends FormatBase {
+    private $_x5c;
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check packed data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+
+        // certificate for validation
+        if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {
+
+            // The attestation certificate attestnCert MUST be the first element in the array
+            $attestnCert = array_shift($attStmt['x5c']);
+
+            if (!($attestnCert instanceof ByteBuffer)) {
+                throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+            }
+
+            $this->_x5c = $attestnCert->getBinaryString();
+
+            // certificate chain
+            foreach ($attStmt['x5c'] as $chain) {
+                if ($chain instanceof ByteBuffer) {
+                    $this->_x5c_chain[] = $chain->getBinaryString();
+                }
+            }
+        } else {
+            throw new WebAuthnException('invalid Apple attestation statement: missing x5c', WebAuthnException::INVALID_DATA);
+        }
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string|null
+     */
+    public function getCertificatePem() {
+        return $this->_createCertificatePem($this->_x5c);
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        return $this->_validateOverX5c($clientDataHash);
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+
+    /**
+     * validate if x5c is present
+     * @param string $clientDataHash
+     * @return bool
+     * @throws WebAuthnException
+     */
+    protected function _validateOverX5c($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        if ($publicKey === false) {
+            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        // Concatenate authenticatorData and clientDataHash to form nonceToHash.
+        $nonceToHash = $this->_authenticatorData->getBinary();
+        $nonceToHash .= $clientDataHash;
+
+        // Perform SHA-256 hash of nonceToHash to produce nonce
+        $nonce = hash('SHA256', $nonceToHash, true);
+
+        $credCert = openssl_x509_read($this->getCertificatePem());
+        if ($credCert === false) {
+            throw new WebAuthnException('invalid x5c certificate: ' . \openssl_error_string(), WebAuthnException::INVALID_DATA);
+        }
+
+        $keyData = openssl_pkey_get_details(openssl_pkey_get_public($credCert));
+        $key = is_array($keyData) && array_key_exists('key', $keyData) ? $keyData['key'] : null;
+
+
+        // Verify that nonce equals the value of the extension with OID ( 1.2.840.113635.100.8.2 ) in credCert.
+        $parsedCredCert = openssl_x509_parse($credCert);
+        $nonceExtension = $parsedCredCert['extensions']['1.2.840.113635.100.8.2'] ?? '';
+
+        // nonce padded by ASN.1 string: 30 24 A1 22 04 20
+        // 30     — type tag indicating sequence
+        // 24     — 36 byte following
+        //   A1   — Enumerated [1]
+        //   22   — 34 byte following
+        //     04 — type tag indicating octet string
+        //     20 — 32 byte following
+
+        $asn1Padding = "\x30\x24\xA1\x22\x04\x20";
+        if (substr($nonceExtension, 0, strlen($asn1Padding)) === $asn1Padding) {
+            $nonceExtension = substr($nonceExtension, strlen($asn1Padding));
+        }
+
+        if ($nonceExtension !== $nonce) {
+            throw new WebAuthnException('nonce doesn\'t equal the value of the extension with OID 1.2.840.113635.100.8.2', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify that the credential public key equals the Subject Public Key of credCert.
+        $authKeyData = openssl_pkey_get_details(openssl_pkey_get_public($this->_authenticatorData->getPublicKeyPem()));
+        $authKey = is_array($authKeyData) && array_key_exists('key', $authKeyData) ? $authKeyData['key'] : null;
+
+        if ($key === null || $key !== $authKey) {
+            throw new WebAuthnException('credential public key doesn\'t equal the Subject Public Key of credCert', WebAuthnException::INVALID_DATA);
+        }
+
+        return true;
+    }
+
+}
+
diff --git a/src/lib/WebAuthn/Attestation/Format/FormatBase.php b/src/lib/WebAuthn/Attestation/Format/FormatBase.php
new file mode 100644
index 0000000..eed916b
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/FormatBase.php
@@ -0,0 +1,193 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+
+
+abstract class FormatBase {
+    protected $_attestationObject = null;
+    protected $_authenticatorData = null;
+    protected $_x5c_chain = array();
+    protected $_x5c_tempFile = null;
+
+    /**
+     *
+     * @param Array $AttestionObject
+     * @param AuthenticatorData $authenticatorData
+     */
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        $this->_attestationObject = $AttestionObject;
+        $this->_authenticatorData = $authenticatorData;
+    }
+
+    /**
+     *
+     */
+    public function __destruct() {
+        // delete X.509 chain certificate file after use
+        if ($this->_x5c_tempFile && \is_file($this->_x5c_tempFile)) {
+            \unlink($this->_x5c_tempFile);
+        }
+    }
+
+    /**
+     * returns the certificate chain in PEM format
+     * @return string|null
+     */
+    public function getCertificateChain() {
+        if ($this->_x5c_tempFile && \is_file($this->_x5c_tempFile)) {
+            return \file_get_contents($this->_x5c_tempFile);
+        }
+        return null;
+    }
+
+    /**
+     * returns the key X.509 certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        // need to be overwritten
+        return null;
+    }
+
+    /**
+     * checks validity of the signature
+     * @param string $clientDataHash
+     * @return bool
+     * @throws WebAuthnException
+     */
+    public function validateAttestation($clientDataHash) {
+        // need to be overwritten
+        return false;
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        // need to be overwritten
+        return false;
+    }
+
+
+    /**
+     * create a PEM encoded certificate with X.509 binary data
+     * @param string $x5c
+     * @return string
+     */
+    protected function _createCertificatePem($x5c) {
+        $pem = '-----BEGIN CERTIFICATE-----' . "\n";
+        $pem .= \chunk_split(\base64_encode($x5c), 64, "\n");
+        $pem .= '-----END CERTIFICATE-----' . "\n";
+        return $pem;
+    }
+
+    /**
+     * creates a PEM encoded chain file
+     * @return type
+     */
+    protected function _createX5cChainFile() {
+        $content = '';
+        if (\is_array($this->_x5c_chain) && \count($this->_x5c_chain) > 0) {
+            foreach ($this->_x5c_chain as $x5c) {
+                $certInfo = \openssl_x509_parse($this->_createCertificatePem($x5c));
+
+                // check if certificate is self signed
+                if (\is_array($certInfo) && \is_array($certInfo['issuer']) && \is_array($certInfo['subject'])) {
+                    $selfSigned = false;
+
+                    $subjectKeyIdentifier = $certInfo['extensions']['subjectKeyIdentifier'] ?? null;
+                    $authorityKeyIdentifier = $certInfo['extensions']['authorityKeyIdentifier'] ?? null;
+
+                    if ($authorityKeyIdentifier && substr($authorityKeyIdentifier, 0, 6) === 'keyid:') {
+                        $authorityKeyIdentifier = substr($authorityKeyIdentifier, 6);
+                    }
+                    if ($subjectKeyIdentifier && substr($subjectKeyIdentifier, 0, 6) === 'keyid:') {
+                        $subjectKeyIdentifier = substr($subjectKeyIdentifier, 6);
+                    }
+
+                    if (($subjectKeyIdentifier && !$authorityKeyIdentifier) || ($authorityKeyIdentifier && $authorityKeyIdentifier === $subjectKeyIdentifier)) {
+                        $selfSigned = true;
+                    }
+
+                    if (!$selfSigned) {
+                        $content .= "\n" . $this->_createCertificatePem($x5c) . "\n";
+                    }
+                }
+            }
+        }
+
+        if ($content) {
+            $this->_x5c_tempFile = \sys_get_temp_dir() . '/x5c_chain_' . \base_convert(\rand(), 10, 36) . '.pem';
+            if (\file_put_contents($this->_x5c_tempFile, $content) !== false) {
+                return $this->_x5c_tempFile;
+            }
+        }
+
+        return null;
+    }
+
+
+    /**
+     * returns the name and openssl key for provided cose number.
+     * @param int $coseNumber
+     * @return \stdClass|null
+     */
+    protected function _getCoseAlgorithm($coseNumber) {
+        // https://www.iana.org/assignments/cose/cose.xhtml#algorithms
+        $coseAlgorithms = array(
+            array(
+                'hash' => 'SHA1',
+                'openssl' => OPENSSL_ALGO_SHA1,
+                'cose' => array(
+                    -65535  // RS1
+                )),
+
+            array(
+                'hash' => 'SHA256',
+                'openssl' => OPENSSL_ALGO_SHA256,
+                'cose' => array(
+                    -257, // RS256
+                    -37,  // PS256
+                    -7,   // ES256
+                    5     // HMAC256
+                )),
+
+            array(
+                'hash' => 'SHA384',
+                'openssl' => OPENSSL_ALGO_SHA384,
+                'cose' => array(
+                    -258, // RS384
+                    -38,  // PS384
+                    -35,  // ES384
+                    6     // HMAC384
+                )),
+
+            array(
+                'hash' => 'SHA512',
+                'openssl' => OPENSSL_ALGO_SHA512,
+                'cose' => array(
+                    -259, // RS512
+                    -39,  // PS512
+                    -36,  // ES512
+                    7     // HMAC512
+                ))
+        );
+
+        foreach ($coseAlgorithms as $coseAlgorithm) {
+            if (\in_array($coseNumber, $coseAlgorithm['cose'], true)) {
+                $return = new \stdClass();
+                $return->hash = $coseAlgorithm['hash'];
+                $return->openssl = $coseAlgorithm['openssl'];
+                return $return;
+            }
+        }
+
+        return null;
+    }
+}
diff --git a/src/lib/WebAuthn/Attestation/Format/None.php b/src/lib/WebAuthn/Attestation/Format/None.php
new file mode 100644
index 0000000..ba95e40
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/None.php
@@ -0,0 +1,41 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+
+class None extends FormatBase {
+
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        return null;
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        return true;
+    }
+
+    /**
+     * validates the certificate against root certificates.
+     * Format 'none' does not contain any ca, so always false.
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        return false;
+    }
+}
diff --git a/src/lib/WebAuthn/Attestation/Format/Packed.php b/src/lib/WebAuthn/Attestation/Format/Packed.php
new file mode 100644
index 0000000..c2ced07
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/Packed.php
@@ -0,0 +1,139 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class Packed extends FormatBase {
+    private $_alg;
+    private $_signature;
+    private $_x5c;
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check packed data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+        if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
+            throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_alg = $attStmt['alg'];
+        $this->_signature = $attStmt['sig']->getBinaryString();
+
+        // certificate for validation
+        if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {
+
+            // The attestation certificate attestnCert MUST be the first element in the array
+            $attestnCert = array_shift($attStmt['x5c']);
+
+            if (!($attestnCert instanceof ByteBuffer)) {
+                throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+            }
+
+            $this->_x5c = $attestnCert->getBinaryString();
+
+            // certificate chain
+            foreach ($attStmt['x5c'] as $chain) {
+                if ($chain instanceof ByteBuffer) {
+                    $this->_x5c_chain[] = $chain->getBinaryString();
+                }
+            }
+        }
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string|null
+     */
+    public function getCertificatePem() {
+        if (!$this->_x5c) {
+            return null;
+        }
+        return $this->_createCertificatePem($this->_x5c);
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        if ($this->_x5c) {
+            return $this->_validateOverX5c($clientDataHash);
+        } else {
+            return $this->_validateSelfAttestation($clientDataHash);
+        }
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        if (!$this->_x5c) {
+            return false;
+        }
+
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+
+    /**
+     * validate if x5c is present
+     * @param string $clientDataHash
+     * @return bool
+     * @throws WebAuthnException
+     */
+    protected function _validateOverX5c($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        if ($publicKey === false) {
+            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
+        // using the attestation public key in attestnCert with the algorithm specified in alg.
+        $dataToVerify = $this->_authenticatorData->getBinary();
+        $dataToVerify .= $clientDataHash;
+
+        $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
+
+        // check certificate
+        return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
+    }
+
+    /**
+     * validate if self attestation is in use
+     * @param string $clientDataHash
+     * @return bool
+     */
+    protected function _validateSelfAttestation($clientDataHash) {
+        // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
+        // using the credential public key with alg.
+        $dataToVerify = $this->_authenticatorData->getBinary();
+        $dataToVerify .= $clientDataHash;
+
+        $publicKey = $this->_authenticatorData->getPublicKeyPem();
+
+        // check certificate
+        return \openssl_verify($dataToVerify, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 1;
+    }
+}
+
diff --git a/src/lib/WebAuthn/Attestation/Format/Tpm.php b/src/lib/WebAuthn/Attestation/Format/Tpm.php
new file mode 100644
index 0000000..338cd45
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/Tpm.php
@@ -0,0 +1,180 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class Tpm extends FormatBase {
+    private $_TPM_GENERATED_VALUE = "\xFF\x54\x43\x47";
+    private $_TPM_ST_ATTEST_CERTIFY = "\x80\x17";
+    private $_alg;
+    private $_signature;
+    private $_pubArea;
+    private $_x5c;
+
+    /**
+     * @var ByteBuffer
+     */
+    private $_certInfo;
+
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check packed data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+        if (!\array_key_exists('ver', $attStmt) || $attStmt['ver'] !== '2.0') {
+            throw new WebAuthnException('invalid tpm version: ' . $attStmt['ver'], WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
+            throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('signature not found', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('certInfo', $attStmt) || !\is_object($attStmt['certInfo']) || !($attStmt['certInfo'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('certInfo not found', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('pubArea', $attStmt) || !\is_object($attStmt['pubArea']) || !($attStmt['pubArea'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('pubArea not found', WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_alg = $attStmt['alg'];
+        $this->_signature = $attStmt['sig']->getBinaryString();
+        $this->_certInfo = $attStmt['certInfo'];
+        $this->_pubArea = $attStmt['pubArea'];
+
+        // certificate for validation
+        if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {
+
+            // The attestation certificate attestnCert MUST be the first element in the array
+            $attestnCert = array_shift($attStmt['x5c']);
+
+            if (!($attestnCert instanceof ByteBuffer)) {
+                throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+            }
+
+            $this->_x5c = $attestnCert->getBinaryString();
+
+            // certificate chain
+            foreach ($attStmt['x5c'] as $chain) {
+                if ($chain instanceof ByteBuffer) {
+                    $this->_x5c_chain[] = $chain->getBinaryString();
+                }
+            }
+
+        } else {
+            throw new WebAuthnException('no x5c certificate found', WebAuthnException::INVALID_DATA);
+        }
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string|null
+     */
+    public function getCertificatePem() {
+        if (!$this->_x5c) {
+            return null;
+        }
+        return $this->_createCertificatePem($this->_x5c);
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        return $this->_validateOverX5c($clientDataHash);
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        if (!$this->_x5c) {
+            return false;
+        }
+
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+
+    /**
+     * validate if x5c is present
+     * @param string $clientDataHash
+     * @return bool
+     * @throws WebAuthnException
+     */
+    protected function _validateOverX5c($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        if ($publicKey === false) {
+            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        // Concatenate authenticatorData and clientDataHash to form attToBeSigned.
+        $attToBeSigned = $this->_authenticatorData->getBinary();
+        $attToBeSigned .= $clientDataHash;
+
+        // Validate that certInfo is valid:
+
+        // Verify that magic is set to TPM_GENERATED_VALUE.
+        if ($this->_certInfo->getBytes(0, 4) !== $this->_TPM_GENERATED_VALUE) {
+            throw new WebAuthnException('tpm magic not TPM_GENERATED_VALUE', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify that type is set to TPM_ST_ATTEST_CERTIFY.
+        if ($this->_certInfo->getBytes(4, 2) !== $this->_TPM_ST_ATTEST_CERTIFY) {
+            throw new WebAuthnException('tpm type not TPM_ST_ATTEST_CERTIFY', WebAuthnException::INVALID_DATA);
+        }
+
+        $offset = 6;
+        $qualifiedSigner = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);
+        $extraData = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);
+        $coseAlg = $this->_getCoseAlgorithm($this->_alg);
+
+        // Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".
+        if ($extraData->getBinaryString() !== \hash($coseAlg->hash, $attToBeSigned, true)) {
+            throw new WebAuthnException('certInfo:extraData not hash of attToBeSigned', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify the sig is a valid signature over certInfo using the attestation
+        // public key in aikCert with the algorithm specified in alg.
+        return \openssl_verify($this->_certInfo->getBinaryString(), $this->_signature, $publicKey, $coseAlg->openssl) === 1;
+    }
+
+
+    /**
+     * returns next part of ByteBuffer
+     * @param ByteBuffer $buffer
+     * @param int $offset
+     * @return ByteBuffer
+     */
+    protected function _tpmReadLengthPrefixed(ByteBuffer $buffer, &$offset) {
+        $len = $buffer->getUint16Val($offset);
+        $data = $buffer->getBytes($offset + 2, $len);
+        $offset += (2 + $len);
+
+        return new ByteBuffer($data);
+    }
+
+}
+
diff --git a/src/lib/WebAuthn/Attestation/Format/U2f.php b/src/lib/WebAuthn/Attestation/Format/U2f.php
new file mode 100644
index 0000000..2b51ba8
--- /dev/null
+++ b/src/lib/WebAuthn/Attestation/Format/U2f.php
@@ -0,0 +1,93 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Attestation\Format;
+use lbuchs\WebAuthn\Attestation\AuthenticatorData;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+class U2f extends FormatBase {
+    private $_alg = -7;
+    private $_signature;
+    private $_x5c;
+
+    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
+        parent::__construct($AttestionObject, $authenticatorData);
+
+        // check u2f data
+        $attStmt = $this->_attestationObject['attStmt'];
+
+        if (\array_key_exists('alg', $attStmt) && $attStmt['alg'] !== $this->_alg) {
+            throw new WebAuthnException('u2f only accepts algorithm -7 ("ES256"), but got ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
+            throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) !== 1) {
+            throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+        }
+
+        if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
+            throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
+        }
+
+        $this->_signature = $attStmt['sig']->getBinaryString();
+        $this->_x5c = $attStmt['x5c'][0]->getBinaryString();
+    }
+
+
+    /*
+     * returns the key certificate in PEM format
+     * @return string
+     */
+    public function getCertificatePem() {
+        $pem = '-----BEGIN CERTIFICATE-----' . "\n";
+        $pem .= \chunk_split(\base64_encode($this->_x5c), 64, "\n");
+        $pem .= '-----END CERTIFICATE-----' . "\n";
+        return $pem;
+    }
+
+    /**
+     * @param string $clientDataHash
+     */
+    public function validateAttestation($clientDataHash) {
+        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
+
+        if ($publicKey === false) {
+            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        // Let verificationData be the concatenation of (0x00 || rpIdHash || clientDataHash || credentialId || publicKeyU2F)
+        $dataToVerify = "\x00";
+        $dataToVerify .= $this->_authenticatorData->getRpIdHash();
+        $dataToVerify .= $clientDataHash;
+        $dataToVerify .= $this->_authenticatorData->getCredentialId();
+        $dataToVerify .= $this->_authenticatorData->getPublicKeyU2F();
+
+        $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
+
+        // check certificate
+        return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
+    }
+
+    /**
+     * validates the certificate against root certificates
+     * @param array $rootCas
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    public function validateRootCertificate($rootCas) {
+        $chainC = $this->_createX5cChainFile();
+        if ($chainC) {
+            $rootCas[] = $chainC;
+        }
+
+        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
+        if ($v === -1) {
+            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+        return $v;
+    }
+}
diff --git a/src/lib/WebAuthn/Binary/ByteBuffer.php b/src/lib/WebAuthn/Binary/ByteBuffer.php
new file mode 100644
index 0000000..861ed60
--- /dev/null
+++ b/src/lib/WebAuthn/Binary/ByteBuffer.php
@@ -0,0 +1,300 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\Binary;
+use lbuchs\WebAuthn\WebAuthnException;
+
+/**
+ * Modified version of https://github.com/madwizard-thomas/webauthn-server/blob/master/src/Format/ByteBuffer.php
+ * Copyright © 2018 Thomas Bleeker - MIT licensed
+ * Modified by Lukas Buchs
+ * Thanks Thomas for your work!
+ */
+class ByteBuffer implements \JsonSerializable, \Serializable {
+    /**
+     * @var bool
+     */
+    public static $useBase64UrlEncoding = false;
+
+    /**
+     * @var string
+     */
+    private $_data;
+
+    /**
+     * @var int
+     */
+    private $_length;
+
+    public function __construct($binaryData) {
+        $this->_data = (string)$binaryData;
+        $this->_length = \strlen($binaryData);
+    }
+
+
+    // -----------------------
+    // PUBLIC STATIC
+    // -----------------------
+
+    /**
+     * create a ByteBuffer from a base64 url encoded string
+     * @param string $base64url
+     * @return ByteBuffer
+     */
+    public static function fromBase64Url($base64url): ByteBuffer {
+        $bin = self::_base64url_decode($base64url);
+        if ($bin === false) {
+            throw new WebAuthnException('ByteBuffer: Invalid base64 url string', WebAuthnException::BYTEBUFFER);
+        }
+        return new ByteBuffer($bin);
+    }
+
+    /**
+     * create a ByteBuffer from a base64 url encoded string
+     * @param string $hex
+     * @return ByteBuffer
+     */
+    public static function fromHex($hex): ByteBuffer {
+        $bin = \hex2bin($hex);
+        if ($bin === false) {
+            throw new WebAuthnException('ByteBuffer: Invalid hex string', WebAuthnException::BYTEBUFFER);
+        }
+        return new ByteBuffer($bin);
+    }
+
+    /**
+     * create a random ByteBuffer
+     * @param string $length
+     * @return ByteBuffer
+     */
+    public static function randomBuffer($length): ByteBuffer {
+        if (\function_exists('random_bytes')) { // >PHP 7.0
+            return new ByteBuffer(\random_bytes($length));
+
+        } else if (\function_exists('openssl_random_pseudo_bytes')) {
+            return new ByteBuffer(\openssl_random_pseudo_bytes($length));
+
+        } else {
+            throw new WebAuthnException('ByteBuffer: cannot generate random bytes', WebAuthnException::BYTEBUFFER);
+        }
+    }
+
+    // -----------------------
+    // PUBLIC
+    // -----------------------
+
+    public function getBytes($offset, $length): string {
+        if ($offset < 0 || $length < 0 || ($offset + $length > $this->_length)) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset or length', WebAuthnException::BYTEBUFFER);
+        }
+        return \substr($this->_data, $offset, $length);
+    }
+
+    public function getByteVal($offset): int {
+        if ($offset < 0 || $offset >= $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        return \ord(\substr($this->_data, $offset, 1));
+    }
+
+    public function getJson($jsonFlags=0) {
+        $data = \json_decode($this->getBinaryString(), null, 512, $jsonFlags);
+        if (\json_last_error() !== JSON_ERROR_NONE) {
+            throw new WebAuthnException(\json_last_error_msg(), WebAuthnException::BYTEBUFFER);
+        }
+        return $data;
+    }
+
+    public function getLength(): int {
+        return $this->_length;
+    }
+
+    public function getUint16Val($offset) {
+        if ($offset < 0 || ($offset + 2) > $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        return unpack('n', $this->_data, $offset)[1];
+    }
+
+    public function getUint32Val($offset) {
+        if ($offset < 0 || ($offset + 4) > $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        $val = unpack('N', $this->_data, $offset)[1];
+
+        // Signed integer overflow causes signed negative numbers
+        if ($val < 0) {
+            throw new WebAuthnException('ByteBuffer: Value out of integer range.', WebAuthnException::BYTEBUFFER);
+        }
+        return $val;
+    }
+
+    public function getUint64Val($offset) {
+        if (PHP_INT_SIZE < 8) {
+            throw new WebAuthnException('ByteBuffer: 64-bit values not supported by this system', WebAuthnException::BYTEBUFFER);
+        }
+        if ($offset < 0 || ($offset + 8) > $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        $val = unpack('J', $this->_data, $offset)[1];
+
+        // Signed integer overflow causes signed negative numbers
+        if ($val < 0) {
+            throw new WebAuthnException('ByteBuffer: Value out of integer range.', WebAuthnException::BYTEBUFFER);
+        }
+
+        return $val;
+    }
+
+    public function getHalfFloatVal($offset) {
+        //FROM spec pseudo decode_half(unsigned char *halfp)
+        $half = $this->getUint16Val($offset);
+
+        $exp = ($half >> 10) & 0x1f;
+        $mant = $half & 0x3ff;
+
+        if ($exp === 0) {
+            $val = $mant * (2 ** -24);
+        } elseif ($exp !== 31) {
+            $val = ($mant + 1024) * (2 ** ($exp - 25));
+        } else {
+            $val = ($mant === 0) ? INF : NAN;
+        }
+
+        return ($half & 0x8000) ? -$val : $val;
+    }
+
+    public function getFloatVal($offset) {
+        if ($offset < 0 || ($offset + 4) > $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        return unpack('G', $this->_data, $offset)[1];
+    }
+
+    public function getDoubleVal($offset) {
+        if ($offset < 0 || ($offset + 8) > $this->_length) {
+            throw new WebAuthnException('ByteBuffer: Invalid offset', WebAuthnException::BYTEBUFFER);
+        }
+        return unpack('E', $this->_data, $offset)[1];
+    }
+
+    /**
+     * @return string
+     */
+    public function getBinaryString(): string {
+        return $this->_data;
+    }
+
+    /**
+     * @param string|ByteBuffer $buffer
+     * @return bool
+     */
+    public function equals($buffer): bool {
+        if (is_object($buffer) && $buffer instanceof ByteBuffer) {
+            return $buffer->getBinaryString() === $this->getBinaryString();
+
+        } else if (is_string($buffer)) {
+            return $buffer === $this->getBinaryString();
+        }
+        
+        return false;
+    }
+
+    /**
+     * @return string
+     */
+    public function getHex(): string {
+        return \bin2hex($this->_data);
+    }
+
+    /**
+     * @return bool
+     */
+    public function isEmpty(): bool {
+        return $this->_length === 0;
+    }
+
+
+    /**
+     * jsonSerialize interface
+     * return binary data in RFC 1342-Like serialized string
+     * @return string
+     */
+    public function jsonSerialize(): string {
+        if (ByteBuffer::$useBase64UrlEncoding) {
+            return self::_base64url_encode($this->_data);
+
+        } else {
+            return '=?BINARY?B?' . \base64_encode($this->_data) . '?=';
+        }
+    }
+
+    /**
+     * Serializable-Interface
+     * @return string
+     */
+    public function serialize(): string {
+        return \serialize($this->_data);
+    }
+
+    /**
+     * Serializable-Interface
+     * @param string $serialized
+     */
+    public function unserialize($serialized) {
+        $this->_data = \unserialize($serialized);
+        $this->_length = \strlen($this->_data);
+    }
+
+    /**
+     * (PHP 8 deprecates Serializable-Interface)
+     * @return array
+     */
+    public function __serialize(): array {
+        return [
+            'data' => \serialize($this->_data)
+        ];
+    }
+
+    /**
+     * object to string
+     * @return string
+     */
+    public function __toString(): string {
+        return $this->getHex();
+    }
+
+    /**
+     * (PHP 8 deprecates Serializable-Interface)
+     * @param array $data
+     * @return void
+     */
+    public function __unserialize($data) {
+        if ($data && isset($data['data'])) {
+            $this->_data = \unserialize($data['data']);
+            $this->_length = \strlen($this->_data);
+        }
+    }
+
+    // -----------------------
+    // PROTECTED STATIC
+    // -----------------------
+
+    /**
+     * base64 url decoding
+     * @param string $data
+     * @return string
+     */
+    protected static function _base64url_decode($data): string {
+        return \base64_decode(\strtr($data, '-_', '+/') . \str_repeat('=', 3 - (3 + \strlen($data)) % 4));
+    }
+
+    /**
+     * base64 url encoding
+     * @param string $data
+     * @return string
+     */
+    protected static function _base64url_encode($data): string {
+        return \rtrim(\strtr(\base64_encode($data), '+/', '-_'), '=');
+    }
+}
diff --git a/src/lib/WebAuthn/CBOR/CborDecoder.php b/src/lib/WebAuthn/CBOR/CborDecoder.php
new file mode 100644
index 0000000..e6b5427
--- /dev/null
+++ b/src/lib/WebAuthn/CBOR/CborDecoder.php
@@ -0,0 +1,220 @@
+<?php
+
+
+namespace lbuchs\WebAuthn\CBOR;
+use lbuchs\WebAuthn\WebAuthnException;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+
+/**
+ * Modified version of https://github.com/madwizard-thomas/webauthn-server/blob/master/src/Format/CborDecoder.php
+ * Copyright © 2018 Thomas Bleeker - MIT licensed
+ * Modified by Lukas Buchs
+ * Thanks Thomas for your work!
+ */
+class CborDecoder {
+    const CBOR_MAJOR_UNSIGNED_INT = 0;
+    const CBOR_MAJOR_TEXT_STRING = 3;
+    const CBOR_MAJOR_FLOAT_SIMPLE = 7;
+    const CBOR_MAJOR_NEGATIVE_INT = 1;
+    const CBOR_MAJOR_ARRAY = 4;
+    const CBOR_MAJOR_TAG = 6;
+    const CBOR_MAJOR_MAP = 5;
+    const CBOR_MAJOR_BYTE_STRING = 2;
+
+    /**
+     * @param ByteBuffer|string $bufOrBin
+     * @return mixed
+     * @throws WebAuthnException
+     */
+    public static function decode($bufOrBin) {
+        $buf = $bufOrBin instanceof ByteBuffer ? $bufOrBin : new ByteBuffer($bufOrBin);
+
+        $offset = 0;
+        $result = self::_parseItem($buf, $offset);
+        if ($offset !== $buf->getLength()) {
+            throw new WebAuthnException('Unused bytes after data item.', WebAuthnException::CBOR);
+        }
+        return $result;
+    }
+
+    /**
+     * @param ByteBuffer|string $bufOrBin
+     * @param int $startOffset
+     * @param int|null $endOffset
+     * @return mixed
+     */
+    public static function decodeInPlace($bufOrBin, $startOffset, &$endOffset = null) {
+        $buf = $bufOrBin instanceof ByteBuffer ? $bufOrBin : new ByteBuffer($bufOrBin);
+
+        $offset = $startOffset;
+        $data = self::_parseItem($buf, $offset);
+        $endOffset = $offset;
+        return $data;
+    }
+
+    // ---------------------
+    // protected
+    // ---------------------
+
+    /**
+     * @param ByteBuffer $buf
+     * @param int $offset
+     * @return mixed
+     */
+    protected static function _parseItem(ByteBuffer $buf, &$offset) {
+        $first = $buf->getByteVal($offset++);
+        $type = $first >> 5;
+        $val = $first & 0b11111;
+
+        if ($type === self::CBOR_MAJOR_FLOAT_SIMPLE) {
+            return self::_parseFloatSimple($val, $buf, $offset);
+        }
+
+        $val = self::_parseExtraLength($val, $buf, $offset);
+
+        return self::_parseItemData($type, $val, $buf, $offset);
+    }
+
+    protected static function _parseFloatSimple($val, ByteBuffer $buf, &$offset) {
+        switch ($val) {
+            case 24:
+                $val = $buf->getByteVal($offset);
+                $offset++;
+                return self::_parseSimple($val);
+
+            case 25:
+                $floatValue = $buf->getHalfFloatVal($offset);
+                $offset += 2;
+                return $floatValue;
+
+            case 26:
+                $floatValue = $buf->getFloatVal($offset);
+                $offset += 4;
+                return $floatValue;
+
+            case 27:
+                $floatValue = $buf->getDoubleVal($offset);
+                $offset += 8;
+                return $floatValue;
+
+            case 28:
+            case 29:
+            case 30:
+                throw new WebAuthnException('Reserved value used.', WebAuthnException::CBOR);
+
+            case 31:
+                throw new WebAuthnException('Indefinite length is not supported.', WebAuthnException::CBOR);
+        }
+
+        return self::_parseSimple($val);
+    }
+
+    /**
+     * @param int $val
+     * @return mixed
+     * @throws WebAuthnException
+     */
+    protected static function _parseSimple($val) {
+        if ($val === 20) {
+            return false;
+        }
+        if ($val === 21) {
+            return true;
+        }
+        if ($val === 22) {
+            return null;
+        }
+        throw new WebAuthnException(sprintf('Unsupported simple value %d.', $val), WebAuthnException::CBOR);
+    }
+
+    protected static function _parseExtraLength($val, ByteBuffer $buf, &$offset) {
+        switch ($val) {
+            case 24:
+                $val = $buf->getByteVal($offset);
+                $offset++;
+                break;
+
+            case 25:
+                $val = $buf->getUint16Val($offset);
+                $offset += 2;
+                break;
+
+            case 26:
+                $val = $buf->getUint32Val($offset);
+                $offset += 4;
+                break;
+
+            case 27:
+                $val = $buf->getUint64Val($offset);
+                $offset += 8;
+                break;
+
+            case 28:
+            case 29:
+            case 30:
+                throw new WebAuthnException('Reserved value used.', WebAuthnException::CBOR);
+
+            case 31:
+                throw new WebAuthnException('Indefinite length is not supported.', WebAuthnException::CBOR);
+        }
+
+        return $val;
+    }
+
+    protected static function _parseItemData($type, $val, ByteBuffer $buf, &$offset) {
+        switch ($type) {
+            case self::CBOR_MAJOR_UNSIGNED_INT: // uint
+                return $val;
+
+            case self::CBOR_MAJOR_NEGATIVE_INT:
+                return -1 - $val;
+
+            case self::CBOR_MAJOR_BYTE_STRING:
+                $data = $buf->getBytes($offset, $val);
+                $offset += $val;
+                return new ByteBuffer($data); // bytes
+
+            case self::CBOR_MAJOR_TEXT_STRING:
+                $data = $buf->getBytes($offset, $val);
+                $offset += $val;
+                return $data; // UTF-8
+
+            case self::CBOR_MAJOR_ARRAY:
+                return self::_parseArray($buf, $offset, $val);
+
+            case self::CBOR_MAJOR_MAP:
+                return self::_parseMap($buf, $offset, $val);
+
+            case self::CBOR_MAJOR_TAG:
+                return self::_parseItem($buf, $offset); // 1 embedded data item
+        }
+
+        // This should never be reached
+        throw new WebAuthnException(sprintf('Unknown major type %d.', $type), WebAuthnException::CBOR);
+    }
+
+    protected static function _parseMap(ByteBuffer $buf, &$offset, $count) {
+        $map = array();
+
+        for ($i = 0; $i < $count; $i++) {
+            $mapKey = self::_parseItem($buf, $offset);
+            $mapVal = self::_parseItem($buf, $offset);
+
+            if (!\is_int($mapKey) && !\is_string($mapKey)) {
+                throw new WebAuthnException('Can only use strings or integers as map keys', WebAuthnException::CBOR);
+            }
+
+            $map[$mapKey] = $mapVal; // todo dup
+        }
+        return $map;
+    }
+
+    protected static function _parseArray(ByteBuffer $buf, &$offset, $count) {
+        $arr = array();
+        for ($i = 0; $i < $count; $i++) {
+            $arr[] = self::_parseItem($buf, $offset);
+        }
+
+        return $arr;
+    }
+}
diff --git a/src/lib/WebAuthn/LICENSE b/src/lib/WebAuthn/LICENSE
new file mode 100644
index 0000000..0580d1b
--- /dev/null
+++ b/src/lib/WebAuthn/LICENSE
@@ -0,0 +1,22 @@
+MIT License
+
+Copyright © 2022 Lukas Buchs
+Copyright © 2018 Thomas Bleeker (CBOR & ByteBuffer part)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/src/lib/WebAuthn/WebAuthn.php b/src/lib/WebAuthn/WebAuthn.php
new file mode 100644
index 0000000..0da0aa6
--- /dev/null
+++ b/src/lib/WebAuthn/WebAuthn.php
@@ -0,0 +1,677 @@
+<?php
+
+namespace lbuchs\WebAuthn;
+use lbuchs\WebAuthn\Binary\ByteBuffer;
+require_once 'WebAuthnException.php';
+require_once 'Binary/ByteBuffer.php';
+require_once 'Attestation/AttestationObject.php';
+require_once 'Attestation/AuthenticatorData.php';
+require_once 'Attestation/Format/FormatBase.php';
+require_once 'Attestation/Format/None.php';
+require_once 'Attestation/Format/AndroidKey.php';
+require_once 'Attestation/Format/AndroidSafetyNet.php';
+require_once 'Attestation/Format/Apple.php';
+require_once 'Attestation/Format/Packed.php';
+require_once 'Attestation/Format/Tpm.php';
+require_once 'Attestation/Format/U2f.php';
+require_once 'CBOR/CborDecoder.php';
+
+/**
+ * WebAuthn
+ * @author Lukas Buchs
+ * @license https://github.com/lbuchs/WebAuthn/blob/master/LICENSE MIT
+ */
+class WebAuthn {
+    // relying party
+    private $_rpName;
+    private $_rpId;
+    private $_rpIdHash;
+    private $_challenge;
+    private $_signatureCounter;
+    private $_caFiles;
+    private $_formats;
+
+    /**
+     * Initialize a new WebAuthn server
+     * @param string $rpName the relying party name
+     * @param string $rpId the relying party ID = the domain name
+     * @param bool $useBase64UrlEncoding true to use base64 url encoding for binary data in json objects. Default is a RFC 1342-Like serialized string.
+     * @throws WebAuthnException
+     */
+    public function __construct($rpName, $rpId, $allowedFormats=null, $useBase64UrlEncoding=false) {
+        $this->_rpName = $rpName;
+        $this->_rpId = $rpId;
+        $this->_rpIdHash = \hash('sha256', $rpId, true);
+        ByteBuffer::$useBase64UrlEncoding = !!$useBase64UrlEncoding;
+        $supportedFormats = array('android-key', 'android-safetynet', 'apple', 'fido-u2f', 'none', 'packed', 'tpm');
+
+        if (!\function_exists('\openssl_open')) {
+            throw new WebAuthnException('OpenSSL-Module not installed');
+        }
+
+        if (!\in_array('SHA256', \array_map('\strtoupper', \openssl_get_md_methods()))) {
+            throw new WebAuthnException('SHA256 not supported by this openssl installation.');
+        }
+
+        // default: all format
+        if (!is_array($allowedFormats)) {
+            $allowedFormats = $supportedFormats;
+        }
+        $this->_formats = $allowedFormats;
+
+        // validate formats
+        $invalidFormats = \array_diff($this->_formats, $supportedFormats);
+        if (!$this->_formats || $invalidFormats) {
+            throw new WebAuthnException('invalid formats on construct: ' . implode(', ', $invalidFormats));
+        }
+    }
+
+    /**
+     * add a root certificate to verify new registrations
+     * @param string $path file path of / directory with root certificates
+     * @param array|null $certFileExtensions if adding a direction, all files with provided extension are added. default: pem, crt, cer, der
+     */
+    public function addRootCertificates($path, $certFileExtensions=null) {
+        if (!\is_array($this->_caFiles)) {
+            $this->_caFiles = [];
+        }
+        if ($certFileExtensions === null) {
+            $certFileExtensions = array('pem', 'crt', 'cer', 'der');
+        }
+        $path = \rtrim(\trim($path), '\\/');
+        if (\is_dir($path)) {
+            foreach (\scandir($path) as $ca) {
+                if (\is_file($path . DIRECTORY_SEPARATOR . $ca) && \in_array(\strtolower(\pathinfo($ca, PATHINFO_EXTENSION)), $certFileExtensions)) {
+                    $this->addRootCertificates($path . DIRECTORY_SEPARATOR . $ca);
+                }
+            }
+        } else if (\is_file($path) && !\in_array(\realpath($path), $this->_caFiles)) {
+            $this->_caFiles[] = \realpath($path);
+        }
+    }
+
+    /**
+     * Returns the generated challenge to save for later validation
+     * @return ByteBuffer
+     */
+    public function getChallenge() {
+        return $this->_challenge;
+    }
+
+    /**
+     * generates the object for a key registration
+     * provide this data to navigator.credentials.create
+     * @param string $userId
+     * @param string $userName
+     * @param string $userDisplayName
+     * @param int $timeout timeout in seconds
+     * @param bool|string $requireResidentKey      'required', if the key should be stored by the authentication device
+     *                                             Valid values:
+     *                                             true = required
+     *                                             false = preferred
+     *                                             string 'required' 'preferred' 'discouraged'
+     * @param bool|string $requireUserVerification indicates that you require user verification and will fail the operation
+     *                                             if the response does not have the UV flag set.
+     *                                             Valid values:
+     *                                             true = required
+     *                                             false = preferred
+     *                                             string 'required' 'preferred' 'discouraged'
+     * @param bool|null $crossPlatformAttachment   true for cross-platform devices (eg. fido usb),
+     *                                             false for platform devices (eg. windows hello, android safetynet),
+     *                                             null for both
+     * @param array $excludeCredentialIds a array of ids, which are already registered, to prevent re-registration
+     * @return \stdClass
+     */
+    public function getCreateArgs($userId, $userName, $userDisplayName, $timeout=20, $requireResidentKey=false, $requireUserVerification=false, $crossPlatformAttachment=null, $excludeCredentialIds=[]) {
+
+        $args = new \stdClass();
+        $args->publicKey = new \stdClass();
+
+        // relying party
+        $args->publicKey->rp = new \stdClass();
+        $args->publicKey->rp->name = $this->_rpName;
+        $args->publicKey->rp->id = $this->_rpId;
+
+        $args->publicKey->authenticatorSelection = new \stdClass();
+        $args->publicKey->authenticatorSelection->userVerification = 'preferred';
+
+        // validate User Verification Requirement
+        if (\is_bool($requireUserVerification)) {
+            $args->publicKey->authenticatorSelection->userVerification = $requireUserVerification ? 'required' : 'preferred';
+
+        } else if (\is_string($requireUserVerification) && \in_array(\strtolower($requireUserVerification), ['required', 'preferred', 'discouraged'])) {
+            $args->publicKey->authenticatorSelection->userVerification = \strtolower($requireUserVerification);
+        }
+
+        // validate Resident Key Requirement
+        if (\is_bool($requireResidentKey) && $requireResidentKey) {
+            $args->publicKey->authenticatorSelection->requireResidentKey = true;
+            $args->publicKey->authenticatorSelection->residentKey = 'required';
+
+        } else if (\is_string($requireResidentKey) && \in_array(\strtolower($requireResidentKey), ['required', 'preferred', 'discouraged'])) {
+            $requireResidentKey = \strtolower($requireResidentKey);
+            $args->publicKey->authenticatorSelection->residentKey = $requireResidentKey;
+            $args->publicKey->authenticatorSelection->requireResidentKey = $requireResidentKey === 'required';
+        }
+
+        // filte authenticators attached with the specified authenticator attachment modality
+        if (\is_bool($crossPlatformAttachment)) {
+            $args->publicKey->authenticatorSelection->authenticatorAttachment = $crossPlatformAttachment ? 'cross-platform' : 'platform';
+        }
+
+        // user
+        $args->publicKey->user = new \stdClass();
+        $args->publicKey->user->id = new ByteBuffer($userId); // binary
+        $args->publicKey->user->name = $userName;
+        $args->publicKey->user->displayName = $userDisplayName;
+
+        // supported algorithms
+        $args->publicKey->pubKeyCredParams = [];
+
+        if (function_exists('sodium_crypto_sign_verify_detached') || \in_array('ed25519', \openssl_get_curve_names(), true)) {
+            $tmp = new \stdClass();
+            $tmp->type = 'public-key';
+            $tmp->alg = -8; // EdDSA
+            $args->publicKey->pubKeyCredParams[] = $tmp;
+            unset ($tmp);
+        }
+
+        if (\in_array('prime256v1', \openssl_get_curve_names(), true)) {
+            $tmp = new \stdClass();
+            $tmp->type = 'public-key';
+            $tmp->alg = -7; // ES256
+            $args->publicKey->pubKeyCredParams[] = $tmp;
+            unset ($tmp);
+        }
+
+        $tmp = new \stdClass();
+        $tmp->type = 'public-key';
+        $tmp->alg = -257; // RS256
+        $args->publicKey->pubKeyCredParams[] = $tmp;
+        unset ($tmp);
+
+        // if there are root certificates added, we need direct attestation to validate
+        // against the root certificate. If there are no root-certificates added,
+        // anonymization ca are also accepted, because we can't validate the root anyway.
+        $attestation = 'indirect';
+        if (\is_array($this->_caFiles)) {
+            $attestation = 'direct';
+        }
+
+        $args->publicKey->attestation = \count($this->_formats) === 1 && \in_array('none', $this->_formats) ? 'none' : $attestation;
+        $args->publicKey->extensions = new \stdClass();
+        $args->publicKey->extensions->exts = true;
+        $args->publicKey->timeout = $timeout * 1000; // microseconds
+        $args->publicKey->challenge = $this->_createChallenge(); // binary
+
+        //prevent re-registration by specifying existing credentials
+        $args->publicKey->excludeCredentials = [];
+
+        if (is_array($excludeCredentialIds)) {
+            foreach ($excludeCredentialIds as $id) {
+                $tmp = new \stdClass();
+                $tmp->id = $id instanceof ByteBuffer ? $id : new ByteBuffer($id);  // binary
+                $tmp->type = 'public-key';
+                $tmp->transports = array('usb', 'nfc', 'ble', 'hybrid', 'internal');
+                $args->publicKey->excludeCredentials[] = $tmp;
+                unset ($tmp);
+            }
+        }
+
+        return $args;
+    }
+
+    /**
+     * generates the object for key validation
+     * Provide this data to navigator.credentials.get
+     * @param array $credentialIds binary
+     * @param int $timeout timeout in seconds
+     * @param bool $allowUsb allow removable USB
+     * @param bool $allowNfc allow Near Field Communication (NFC)
+     * @param bool $allowBle allow Bluetooth
+     * @param bool $allowHybrid allow a combination of (often separate) data-transport and proximity mechanisms.
+     * @param bool $allowInternal allow client device-specific transport. These authenticators are not removable from the client device.
+     * @param bool|string $requireUserVerification indicates that you require user verification and will fail the operation
+     *                                             if the response does not have the UV flag set.
+     *                                             Valid values:
+     *                                             true = required
+     *                                             false = preferred
+     *                                             string 'required' 'preferred' 'discouraged'
+     * @return \stdClass
+     */
+    public function getGetArgs($credentialIds=[], $timeout=20, $allowUsb=true, $allowNfc=true, $allowBle=true, $allowHybrid=true, $allowInternal=true, $requireUserVerification=false) {
+
+        // validate User Verification Requirement
+        if (\is_bool($requireUserVerification)) {
+            $requireUserVerification = $requireUserVerification ? 'required' : 'preferred';
+        } else if (\is_string($requireUserVerification) && \in_array(\strtolower($requireUserVerification), ['required', 'preferred', 'discouraged'])) {
+            $requireUserVerification = \strtolower($requireUserVerification);
+        } else {
+            $requireUserVerification = 'preferred';
+        }
+
+        $args = new \stdClass();
+        $args->publicKey = new \stdClass();
+        $args->publicKey->timeout = $timeout * 1000; // microseconds
+        $args->publicKey->challenge = $this->_createChallenge();  // binary
+        $args->publicKey->userVerification = $requireUserVerification;
+        $args->publicKey->rpId = $this->_rpId;
+
+        if (\is_array($credentialIds) && \count($credentialIds) > 0) {
+            $args->publicKey->allowCredentials = [];
+
+            foreach ($credentialIds as $id) {
+                $tmp = new \stdClass();
+                $tmp->id = $id instanceof ByteBuffer ? $id : new ByteBuffer($id);  // binary
+                $tmp->transports = [];
+
+                if ($allowUsb) {
+                    $tmp->transports[] = 'usb';
+                }
+                if ($allowNfc) {
+                    $tmp->transports[] = 'nfc';
+                }
+                if ($allowBle) {
+                    $tmp->transports[] = 'ble';
+                }
+                if ($allowHybrid) {
+                    $tmp->transports[] = 'hybrid';
+                }
+                if ($allowInternal) {
+                    $tmp->transports[] = 'internal';
+                }
+
+                $tmp->type = 'public-key';
+                $args->publicKey->allowCredentials[] = $tmp;
+                unset ($tmp);
+            }
+        }
+
+        return $args;
+    }
+
+    /**
+     * returns the new signature counter value.
+     * returns null if there is no counter
+     * @return ?int
+     */
+    public function getSignatureCounter() {
+        return \is_int($this->_signatureCounter) ? $this->_signatureCounter : null;
+    }
+
+    /**
+     * process a create request and returns data to save for future logins
+     * @param string $clientDataJSON binary from browser
+     * @param string $attestationObject binary from browser
+     * @param string|ByteBuffer $challenge binary used challange
+     * @param bool $requireUserVerification true, if the device must verify user (e.g. by biometric data or pin)
+     * @param bool $requireUserPresent false, if the device must NOT check user presence (e.g. by pressing a button)
+     * @param bool $failIfRootMismatch false, if there should be no error thrown if root certificate doesn't match
+     * @param bool $requireCtsProfileMatch false, if you don't want to check if the device is approved as a Google-certified Android device.
+     * @return \stdClass
+     * @throws WebAuthnException
+     */
+    public function processCreate($clientDataJSON, $attestationObject, $challenge, $requireUserVerification=false, $requireUserPresent=true, $failIfRootMismatch=true, $requireCtsProfileMatch=true) {
+        $clientDataHash = \hash('sha256', $clientDataJSON, true);
+        $clientData = \json_decode($clientDataJSON);
+        $challenge = $challenge instanceof ByteBuffer ? $challenge : new ByteBuffer($challenge);
+
+        // security: https://www.w3.org/TR/webauthn/#registering-a-new-credential
+
+        // 2. Let C, the client data claimed as collected during the credential creation,
+        //    be the result of running an implementation-specific JSON parser on JSONtext.
+        if (!\is_object($clientData)) {
+            throw new WebAuthnException('invalid client data', WebAuthnException::INVALID_DATA);
+        }
+
+        // 3. Verify that the value of C.type is webauthn.create.
+        if (!\property_exists($clientData, 'type') || $clientData->type !== 'webauthn.create') {
+            throw new WebAuthnException('invalid type', WebAuthnException::INVALID_TYPE);
+        }
+
+        // 4. Verify that the value of C.challenge matches the challenge that was sent to the authenticator in the create() call.
+        if (!\property_exists($clientData, 'challenge') || ByteBuffer::fromBase64Url($clientData->challenge)->getBinaryString() !== $challenge->getBinaryString()) {
+            throw new WebAuthnException('invalid challenge', WebAuthnException::INVALID_CHALLENGE);
+        }
+
+        // 5. Verify that the value of C.origin matches the Relying Party's origin.
+        if (!\property_exists($clientData, 'origin') || !$this->_checkOrigin($clientData->origin)) {
+            throw new WebAuthnException('invalid origin', WebAuthnException::INVALID_ORIGIN);
+        }
+
+        // Attestation
+        $attestationObject = new Attestation\AttestationObject($attestationObject, $this->_formats);
+
+        // 9. Verify that the RP ID hash in authData is indeed the SHA-256 hash of the RP ID expected by the RP.
+        if (!$attestationObject->validateRpIdHash($this->_rpIdHash)) {
+            throw new WebAuthnException('invalid rpId hash', WebAuthnException::INVALID_RELYING_PARTY);
+        }
+
+        // 14. Verify that attStmt is a correct attestation statement, conveying a valid attestation signature
+        if (!$attestationObject->validateAttestation($clientDataHash)) {
+            throw new WebAuthnException('invalid certificate signature', WebAuthnException::INVALID_SIGNATURE);
+        }
+
+        // Android-SafetyNet: if required, check for Compatibility Testing Suite (CTS).
+        if ($requireCtsProfileMatch && $attestationObject->getAttestationFormat() instanceof Attestation\Format\AndroidSafetyNet) {
+            if (!$attestationObject->getAttestationFormat()->ctsProfileMatch()) {
+                 throw new WebAuthnException('invalid ctsProfileMatch: device is not approved as a Google-certified Android device.', WebAuthnException::ANDROID_NOT_TRUSTED);
+            }
+        }
+
+        // 15. If validation is successful, obtain a list of acceptable trust anchors
+        $rootValid = is_array($this->_caFiles) ? $attestationObject->validateRootCertificate($this->_caFiles) : null;
+        if ($failIfRootMismatch && is_array($this->_caFiles) && !$rootValid) {
+            throw new WebAuthnException('invalid root certificate', WebAuthnException::CERTIFICATE_NOT_TRUSTED);
+        }
+
+        // 10. Verify that the User Present bit of the flags in authData is set.
+        $userPresent = $attestationObject->getAuthenticatorData()->getUserPresent();
+        if ($requireUserPresent && !$userPresent) {
+            throw new WebAuthnException('user not present during authentication', WebAuthnException::USER_PRESENT);
+        }
+
+        // 11. If user verification is required for this registration, verify that the User Verified bit of the flags in authData is set.
+        $userVerified = $attestationObject->getAuthenticatorData()->getUserVerified();
+        if ($requireUserVerification && !$userVerified) {
+            throw new WebAuthnException('user not verified during authentication', WebAuthnException::USER_VERIFICATED);
+        }
+
+        $signCount = $attestationObject->getAuthenticatorData()->getSignCount();
+        if ($signCount > 0) {
+            $this->_signatureCounter = $signCount;
+        }
+
+        // prepare data to store for future logins
+        $data = new \stdClass();
+        $data->rpId = $this->_rpId;
+        $data->attestationFormat = $attestationObject->getAttestationFormatName();
+        $data->credentialId = $attestationObject->getAuthenticatorData()->getCredentialId();
+        $data->credentialPublicKey = $attestationObject->getAuthenticatorData()->getPublicKeyPem();
+        $data->certificateChain = $attestationObject->getCertificateChain();
+        $data->certificate = $attestationObject->getCertificatePem();
+        $data->certificateIssuer = $attestationObject->getCertificateIssuer();
+        $data->certificateSubject = $attestationObject->getCertificateSubject();
+        $data->signatureCounter = $this->_signatureCounter;
+        $data->AAGUID = $attestationObject->getAuthenticatorData()->getAAGUID();
+        $data->rootValid = $rootValid;
+        $data->userPresent = $userPresent;
+        $data->userVerified = $userVerified;
+        return $data;
+    }
+
+
+    /**
+     * process a get request
+     * @param string $clientDataJSON binary from browser
+     * @param string $authenticatorData binary from browser
+     * @param string $signature binary from browser
+     * @param string $credentialPublicKey string PEM-formated public key from used credentialId
+     * @param string|ByteBuffer $challenge  binary from used challange
+     * @param int $prevSignatureCnt signature count value of the last login
+     * @param bool $requireUserVerification true, if the device must verify user (e.g. by biometric data or pin)
+     * @param bool $requireUserPresent true, if the device must check user presence (e.g. by pressing a button)
+     * @return boolean true if get is successful
+     * @throws WebAuthnException
+     */
+    public function processGet($clientDataJSON, $authenticatorData, $signature, $credentialPublicKey, $challenge, $prevSignatureCnt=null, $requireUserVerification=false, $requireUserPresent=true) {
+        $authenticatorObj = new Attestation\AuthenticatorData($authenticatorData);
+        $clientDataHash = \hash('sha256', $clientDataJSON, true);
+        $clientData = \json_decode($clientDataJSON);
+        $challenge = $challenge instanceof ByteBuffer ? $challenge : new ByteBuffer($challenge);
+
+        // https://www.w3.org/TR/webauthn/#verifying-assertion
+
+        // 1. If the allowCredentials option was given when this authentication ceremony was initiated,
+        //    verify that credential.id identifies one of the public key credentials that were listed in allowCredentials.
+        //    -> TO BE VERIFIED BY IMPLEMENTATION
+
+        // 2. If credential.response.userHandle is present, verify that the user identified
+        //    by this value is the owner of the public key credential identified by credential.id.
+        //    -> TO BE VERIFIED BY IMPLEMENTATION
+
+        // 3. Using credential’s id attribute (or the corresponding rawId, if base64url encoding is
+        //    inappropriate for your use case), look up the corresponding credential public key.
+        //    -> TO BE LOOKED UP BY IMPLEMENTATION
+
+        // 5. Let JSONtext be the result of running UTF-8 decode on the value of cData.
+        if (!\is_object($clientData)) {
+            throw new WebAuthnException('invalid client data', WebAuthnException::INVALID_DATA);
+        }
+
+        // 7. Verify that the value of C.type is the string webauthn.get.
+        if (!\property_exists($clientData, 'type') || $clientData->type !== 'webauthn.get') {
+            throw new WebAuthnException('invalid type', WebAuthnException::INVALID_TYPE);
+        }
+
+        // 8. Verify that the value of C.challenge matches the challenge that was sent to the
+        //    authenticator in the PublicKeyCredentialRequestOptions passed to the get() call.
+        if (!\property_exists($clientData, 'challenge') || ByteBuffer::fromBase64Url($clientData->challenge)->getBinaryString() !== $challenge->getBinaryString()) {
+            throw new WebAuthnException('invalid challenge', WebAuthnException::INVALID_CHALLENGE);
+        }
+
+        // 9. Verify that the value of C.origin matches the Relying Party's origin.
+        if (!\property_exists($clientData, 'origin') || !$this->_checkOrigin($clientData->origin)) {
+            throw new WebAuthnException('invalid origin', WebAuthnException::INVALID_ORIGIN);
+        }
+
+        // 11. Verify that the rpIdHash in authData is the SHA-256 hash of the RP ID expected by the Relying Party.
+        if ($authenticatorObj->getRpIdHash() !== $this->_rpIdHash) {
+            throw new WebAuthnException('invalid rpId hash', WebAuthnException::INVALID_RELYING_PARTY);
+        }
+
+        // 12. Verify that the User Present bit of the flags in authData is set
+        if ($requireUserPresent && !$authenticatorObj->getUserPresent()) {
+            throw new WebAuthnException('user not present during authentication', WebAuthnException::USER_PRESENT);
+        }
+
+        // 13. If user verification is required for this assertion, verify that the User Verified bit of the flags in authData is set.
+        if ($requireUserVerification && !$authenticatorObj->getUserVerified()) {
+            throw new WebAuthnException('user not verificated during authentication', WebAuthnException::USER_VERIFICATED);
+        }
+
+        // 14. Verify the values of the client extension outputs
+        //     (extensions not implemented)
+
+        // 16. Using the credential public key looked up in step 3, verify that sig is a valid signature
+        //     over the binary concatenation of authData and hash.
+        $dataToVerify = '';
+        $dataToVerify .= $authenticatorData;
+        $dataToVerify .= $clientDataHash;
+
+        if (!$this->_verifySignature($dataToVerify, $signature, $credentialPublicKey)) {
+            throw new WebAuthnException('invalid signature', WebAuthnException::INVALID_SIGNATURE);
+        }
+
+        $signatureCounter = $authenticatorObj->getSignCount();
+        if ($signatureCounter !== 0) {
+            $this->_signatureCounter = $signatureCounter;
+        }
+
+        // 17. If either of the signature counter value authData.signCount or
+        //     previous signature count is nonzero, and if authData.signCount
+        //     less than or equal to previous signature count, it's a signal
+        //     that the authenticator may be cloned
+        if ($prevSignatureCnt !== null) {
+            if ($signatureCounter !== 0 || $prevSignatureCnt !== 0) {
+                if ($prevSignatureCnt >= $signatureCounter) {
+                    throw new WebAuthnException('signature counter not valid', WebAuthnException::SIGNATURE_COUNTER);
+                }
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Downloads root certificates from FIDO Alliance Metadata Service (MDS) to a specific folder
+     * https://fidoalliance.org/metadata/
+     * @param string $certFolder Folder path to save the certificates in PEM format.
+     * @param bool $deleteCerts delete certificates in the target folder before adding the new ones.
+     * @return int number of cetificates
+     * @throws WebAuthnException
+     */
+    public function queryFidoMetaDataService($certFolder, $deleteCerts=true) {
+        $url = 'https://mds.fidoalliance.org/';
+        $raw = null;
+        if (\function_exists('curl_init')) {
+            $ch = \curl_init($url);
+            \curl_setopt($ch, CURLOPT_HEADER, false);
+            \curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+            \curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
+            \curl_setopt($ch, CURLOPT_USERAGENT, 'github.com/lbuchs/WebAuthn - A simple PHP WebAuthn server library');
+            $raw = \curl_exec($ch);
+            \curl_close($ch);
+        } else {
+            $raw = \file_get_contents($url);
+        }
+
+        $certFolder = \rtrim(\realpath($certFolder), '\\/');
+        if (!is_dir($certFolder)) {
+            throw new WebAuthnException('Invalid folder path for query FIDO Alliance Metadata Service');
+        }
+
+        if (!\is_string($raw)) {
+            throw new WebAuthnException('Unable to query FIDO Alliance Metadata Service');
+        }
+
+        $jwt = \explode('.', $raw);
+        if (\count($jwt) !== 3) {
+            throw new WebAuthnException('Invalid JWT from FIDO Alliance Metadata Service');
+        }
+
+        if ($deleteCerts) {
+            foreach (\scandir($certFolder) as $ca) {
+                if (\substr($ca, -4) === '.pem') {
+                    if (\unlink($certFolder . DIRECTORY_SEPARATOR . $ca) === false) {
+                        throw new WebAuthnException('Cannot delete certs in folder for FIDO Alliance Metadata Service');
+                    }
+                }
+            }
+        }
+
+        list($header, $payload, $hash) = $jwt;
+        $payload = Binary\ByteBuffer::fromBase64Url($payload)->getJson();
+
+        $count = 0;
+        if (\is_object($payload) && \property_exists($payload, 'entries') && \is_array($payload->entries)) {
+            foreach ($payload->entries as $entry) {
+                if (\is_object($entry) && \property_exists($entry, 'metadataStatement') && \is_object($entry->metadataStatement)) {
+                    $description = $entry->metadataStatement->description ?? null;
+                    $attestationRootCertificates = $entry->metadataStatement->attestationRootCertificates ?? null;
+
+                    if ($description && $attestationRootCertificates) {
+
+                        // create filename
+                        $certFilename = \preg_replace('/[^a-z0-9]/i', '_', $description);
+                        $certFilename = \trim(\preg_replace('/\_{2,}/i', '_', $certFilename),'_') . '.pem';
+                        $certFilename = \strtolower($certFilename);
+
+                        // add certificate
+                        $certContent = $description . "\n";
+                        $certContent .= \str_repeat('-', \mb_strlen($description)) . "\n";
+
+                        foreach ($attestationRootCertificates as $attestationRootCertificate) {
+                            $attestationRootCertificate = \str_replace(["\n", "\r", ' '], '', \trim($attestationRootCertificate));
+                            $count++;
+                            $certContent .= "\n-----BEGIN CERTIFICATE-----\n";
+                            $certContent .= \chunk_split($attestationRootCertificate, 64, "\n");
+                            $certContent .= "-----END CERTIFICATE-----\n";
+                        }
+
+                        if (\file_put_contents($certFolder . DIRECTORY_SEPARATOR . $certFilename, $certContent) === false) {
+                            throw new WebAuthnException('unable to save certificate from FIDO Alliance Metadata Service');
+                        }
+                    }
+                }
+            }
+        }
+
+        return $count;
+    }
+
+    // -----------------------------------------------
+    // PRIVATE
+    // -----------------------------------------------
+
+    /**
+     * checks if the origin matchs the RP ID
+     * @param string $origin
+     * @return boolean
+     * @throws WebAuthnException
+     */
+    private function _checkOrigin($origin) {
+        // https://www.w3.org/TR/webauthn/#rp-id
+
+        // The origin's scheme must be https
+        if ($this->_rpId !== 'localhost' && \parse_url($origin, PHP_URL_SCHEME) !== 'https') {
+            return false;
+        }
+
+        // extract host from origin
+        $host = \parse_url($origin, PHP_URL_HOST);
+        $host = \trim($host, '.');
+
+        // The RP ID must be equal to the origin's effective domain, or a registrable
+        // domain suffix of the origin's effective domain.
+        return \preg_match('/' . \preg_quote($this->_rpId) . '$/i', $host) === 1;
+    }
+
+    /**
+     * generates a new challange
+     * @param int $length
+     * @return string
+     * @throws WebAuthnException
+     */
+    private function _createChallenge($length = 32) {
+        if (!$this->_challenge) {
+            $this->_challenge = ByteBuffer::randomBuffer($length);
+        }
+        return $this->_challenge;
+    }
+
+    /**
+     * check if the signature is valid.
+     * @param string $dataToVerify
+     * @param string $signature
+     * @param string $credentialPublicKey PEM format
+     * @return bool
+     */
+    private function _verifySignature($dataToVerify, $signature, $credentialPublicKey) {
+
+        // Use Sodium to verify EdDSA 25519 as its not yet supported by openssl
+        if (\function_exists('sodium_crypto_sign_verify_detached') && !\in_array('ed25519', \openssl_get_curve_names(), true)) {
+            $pkParts = [];
+            if (\preg_match('/BEGIN PUBLIC KEY\-+(?:\s|\n|\r)+([^\-]+)(?:\s|\n|\r)*\-+END PUBLIC KEY/i', $credentialPublicKey, $pkParts)) {
+                $rawPk = \base64_decode($pkParts[1]);
+
+                // 30        = der sequence
+                // 2a        = length 42 byte
+                // 30        = der sequence
+                // 05        = lenght 5 byte
+                // 06        = der OID
+                // 03        = OID length 3 byte
+                // 2b 65 70  = OID 1.3.101.112 curveEd25519 (EdDSA 25519 signature algorithm)
+                // 03        = der bit string
+                // 21        = length 33 byte
+                // 00        = null padding
+                // [...]     = 32 byte x-curve
+                $okpPrefix = "\x30\x2a\x30\x05\x06\x03\x2b\x65\x70\x03\x21\x00";
+
+                if ($rawPk && \strlen($rawPk) === 44 && \substr($rawPk,0, \strlen($okpPrefix)) === $okpPrefix) {
+                    $publicKeyXCurve = \substr($rawPk, \strlen($okpPrefix));
+
+                    return \sodium_crypto_sign_verify_detached($signature, $dataToVerify, $publicKeyXCurve);
+                }
+            }
+        }
+
+        // verify with openSSL
+        $publicKey = \openssl_pkey_get_public($credentialPublicKey);
+        if ($publicKey === false) {
+            throw new WebAuthnException('public key invalid', WebAuthnException::INVALID_PUBLIC_KEY);
+        }
+
+        return \openssl_verify($dataToVerify, $signature, $publicKey, OPENSSL_ALGO_SHA256) === 1;
+    }
+}
diff --git a/src/lib/WebAuthn/WebAuthnException.php b/src/lib/WebAuthn/WebAuthnException.php
new file mode 100644
index 0000000..f27eeec
--- /dev/null
+++ b/src/lib/WebAuthn/WebAuthnException.php
@@ -0,0 +1,28 @@
+<?php
+namespace lbuchs\WebAuthn;
+
+/**
+ * @author Lukas Buchs
+ * @license https://github.com/lbuchs/WebAuthn/blob/master/LICENSE MIT
+ */
+class WebAuthnException extends \Exception {
+    const INVALID_DATA = 1;
+    const INVALID_TYPE = 2;
+    const INVALID_CHALLENGE = 3;
+    const INVALID_ORIGIN = 4;
+    const INVALID_RELYING_PARTY = 5;
+    const INVALID_SIGNATURE = 6;
+    const INVALID_PUBLIC_KEY = 7;
+    const CERTIFICATE_NOT_TRUSTED = 8;
+    const USER_PRESENT = 9;
+    const USER_VERIFICATED = 10;
+    const SIGNATURE_COUNTER = 11;
+    const CRYPTO_STRONG = 13;
+    const BYTEBUFFER = 14;
+    const CBOR = 15;
+    const ANDROID_NOT_TRUSTED = 16;
+
+    public function __construct($message = "", $code = 0, $previous = null) {
+        parent::__construct($message, $code, $previous);
+    }
+}