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), '+/', '-_'), '=');
+    }
+}