--- /dev/null
+<?php
+/**
+ * An implementation of the RFC 10833-2 KDF1 Standard key derivation function
+ *
+ * PHP version 5.3
+ *
+ * @category PHPCryptLib
+ * @package Key
+ * @subpackage Derivation
+ * @author Anthony Ferrara <ircmaxell@ircmaxell.com>
+ * @copyright 2011 The Authors
+ * @license http://www.opensource.org/licenses/mit-license.html MIT License
+ * @version Build @@version@@
+ */
+
+namespace CryptLib\Key\Derivation\KDF;
+
+use CryptLib\Hash\Hash;
+
+/**
+ * An implementation of the RFC 10833-2 KDF1 Standard key derivation function
+ *
+ * @category PHPCryptLib
+ * @package Key
+ * @subpackage Derivation
+ * @author Anthony Ferrara <ircmaxell@ircmaxell.com>
+ */
+class KDF1
+ extends \CryptLib\Key\Derivation\AbstractDerivation
+ implements \CryptLib\Key\Derivation\KDF
+{
+
+ /**
+ * Derive a key of the specified length based on the inputted secret
+ *
+ * @param string $secret The secret to base the key on
+ * @param int $length The length of the key to derive
+ * @param string $other Additional data to append to the key
+ *
+ * @return string The generated key
+ */
+ public function derive($secret, $length, $other = '') {
+ $size = Hash::getHashSize($this->hash);
+ $len = ceil($length / $size);
+ $res = '';
+ for ($i = 0; $i < $len; $i++) {
+ $tmp = pack('N', $i);
+ $res .= hash($this->hash, $secret . $tmp . $other, true);
+ }
+ return substr($res, 0, $length);
+ }
+
+}
+