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;
+    }
+}