<?php

/**
 * Pure-PHP implementations of keyed-hash message authentication codes (HMACs) and various cryptographic hashing functions.
 *
 * Uses hash() or mhash() if available and an internal implementation, otherwise.  Currently supports the following:
 *
 * md2, md5, md5-96, sha1, sha1-96, sha256, sha256-96, sha384, and sha512, sha512-96
 *
 * If {@link self::setKey() setKey()} is called, {@link self::hash() hash()} will return the HMAC as opposed to
 * the hash.  If no valid algorithm is provided, sha1 will be used.
 *
 * PHP version 5
 *
 * {@internal The variable names are the same as those in
 * {@link http://tools.ietf.org/html/rfc2104#section-2 RFC2104}.}}
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $hash = new \phpseclib\Crypt\Hash('sha1');
 *
 *    $hash->setKey('abcdefg');
 *
 *    echo base64_encode($hash->hash('abcdefg'));
 * ?>
 * </code>
 *
 * @category  Crypt
 * @package   Hash
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2007 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib\Crypt;

use phpseclib\Math\BigInteger;

/**
 * Pure-PHP implementations of keyed-hash message authentication codes (HMACs) and various cryptographic hashing functions.
 *
 * @package Hash
 * @author  Jim Wigginton <terrafrost@php.net>
 * @access  public
 */
class Hash
{
    /**#@+
     * @access private
     * @see \phpseclib\Crypt\Hash::__construct()
     */
    /**
     * Toggles the internal implementation
     */
    const MODE_INTERNAL = 1;
    /**
     * Toggles the mhash() implementation, which has been deprecated on PHP 5.3.0+.
     */
    const MODE_MHASH = 2;
    /**
     * Toggles the hash() implementation, which works on PHP 5.1.2+.
     */
    const MODE_HASH = 3;
    /**#@-*/

    /**
     * Hash Parameter
     *
     * @see self::setHash()
     * @var int
     * @access private
     */
    var $hashParam;

    /**
     * Byte-length of compression blocks / key (Internal HMAC)
     *
     * @see self::setAlgorithm()
     * @var int
     * @access private
     */
    var $b;

    /**
     * Byte-length of hash output (Internal HMAC)
     *
     * @see self::setHash()
     * @var int
     * @access private
     */
    var $l = false;

    /**
     * Hash Algorithm
     *
     * @see self::setHash()
     * @var string
     * @access private
     */
    var $hash;

    /**
     * Key
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $key = false;

    /**
     * Computed Key
     *
     * @see self::_computeKey()
     * @var string
     * @access private
     */
    var $computedKey = false;

    /**
     * Outer XOR (Internal HMAC)
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $opad;

    /**
     * Inner XOR (Internal HMAC)
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $ipad;

    /**
     * Engine
     *
     * @see self::setHash()
     * @var string
     * @access private
     */
    var $engine;

    /**
     * Default Constructor.
     *
     * @param string $hash
     * @return \phpseclib\Crypt\Hash
     * @access public
     */
    function __construct($hash = 'sha1')
    {
        if (!defined('CRYPT_HASH_MODE')) {
            switch (true) {
                case extension_loaded('hash'):
                    define('CRYPT_HASH_MODE', self::MODE_HASH);
                    break;
                case extension_loaded('mhash'):
                    define('CRYPT_HASH_MODE', self::MODE_MHASH);
                    break;
                default:
                    define('CRYPT_HASH_MODE', self::MODE_INTERNAL);
            }
        }

        $this->setHash($hash);
    }

    /**
     * Sets the key for HMACs
     *
     * Keys can be of any length.
     *
     * @access public
     * @param string $key
     */
    function setKey($key = false)
    {
        $this->key = $key;
        $this->_computeKey();
    }

    /**
     * Pre-compute the key used by the HMAC
     *
     * Quoting http://tools.ietf.org/html/rfc2104#section-2, "Applications that use keys longer than B bytes
     * will first hash the key using H and then use the resultant L byte string as the actual key to HMAC."
     *
     * As documented in https://www.reddit.com/r/PHP/comments/9nct2l/symfonypolyfill_hash_pbkdf2_correct_fix_for/
     * when doing an HMAC multiple times it's faster to compute the hash once instead of computing it during
     * every call
     *
     * @access private
     */
    function _computeKey()
    {
        if ($this->key === false) {
            $this->computedKey = false;
            return;
        }

        if (strlen($this->key) <= $this->b) {
            $this->computedKey = $this->key;
            return;
        }

        switch ($this->engine) {
            case self::MODE_MHASH:
                $this->computedKey = mhash($this->hash, $this->key);
                break;
            case self::MODE_HASH:
                $this->computedKey = hash($this->hash, $this->key, true);
                break;
            case self::MODE_INTERNAL:
                $this->computedKey = call_user_func($this->hash, $this->key);
        }
    }

    /**
     * Gets the hash function.
     *
     * As set by the constructor or by the setHash() method.
     *
     * @access public
     * @return string
     */
    function getHash()
    {
        return $this->hashParam;
    }

    /**
     * Sets the hash function.
     *
     * @access public
     * @param string $hash
     */
    function setHash($hash)
    {
        $this->hashParam = $hash = strtolower($hash);
        switch ($hash) {
            case 'md5-96':
            case 'sha1-96':
            case 'sha256-96':
            case 'sha512-96':
                $hash = substr($hash, 0, -3);
                $this->l = 12; // 96 / 8 = 12
                break;
            case 'md2':
            case 'md5':
                $this->l = 16;
                break;
            case 'sha1':
                $this->l = 20;
                break;
            case 'sha256':
                $this->l = 32;
                break;
            case 'sha384':
                $this->l = 48;
                break;
            case 'sha512':
                $this->l = 64;
        }

        switch ($hash) {
            case 'md2-96':
            case 'md2':
                $this->b = 16;
            case 'md5-96':
            case 'sha1-96':
            case 'sha224-96':
            case 'sha256-96':
            case 'md2':
            case 'md5':
            case 'sha1':
            case 'sha224':
            case 'sha256':
                $this->b = 64;
                break;
            default:
                $this->b = 128;
        }

        switch ($hash) {
            case 'md2':
                $this->engine = CRYPT_HASH_MODE == self::MODE_HASH && in_array('md2', hash_algos()) ?
                    self::MODE_HASH : self::MODE_INTERNAL;
                break;
            case 'sha384':
            case 'sha512':
                $this->engine = CRYPT_HASH_MODE == self::MODE_MHASH ? self::MODE_INTERNAL : CRYPT_HASH_MODE;
                break;
            default:
                $this->engine = CRYPT_HASH_MODE;
        }

        switch ($this->engine) {
            case self::MODE_MHASH:
                switch ($hash) {
                    case 'md5':
                        $this->hash = MHASH_MD5;
                        break;
                    case 'sha256':
                        $this->hash = MHASH_SHA256;
                        break;
                    case 'sha1':
                    default:
                        $this->hash = MHASH_SHA1;
                }
                $this->_computeKey(self::MODE_MHASH);
                return;
            case self::MODE_HASH:
                switch ($hash) {
                    case 'md5':
                        $this->hash = 'md5';
                        return;
                    case 'md2':
                    case 'sha256':
                    case 'sha384':
                    case 'sha512':
                        $this->hash = $hash;
                        return;
                    case 'sha1':
                    default:
                        $this->hash = 'sha1';
                }
                $this->_computeKey(self::MODE_HASH);
                return;
        }

        switch ($hash) {
            case 'md2':
                $this->hash = array($this, '_md2');
                break;
            case 'md5':
                $this->hash = array($this, '_md5');
                break;
            case 'sha256':
                $this->hash = array($this, '_sha256');
                break;
            case 'sha384':
            case 'sha512':
                $this->hash = array($this, '_sha512');
                break;
            case 'sha1':
            default:
                $this->hash = array($this, '_sha1');
        }

        $this->ipad = str_repeat(chr(0x36), $this->b);
        $this->opad = str_repeat(chr(0x5C), $this->b);

        $this->_computeKey(self::MODE_INTERNAL);
    }

    /**
     * Compute the HMAC.
     *
     * @access public
     * @param string $text
     * @return string
     */
    function hash($text)
    {
        if (!empty($this->key) || is_string($this->key)) {
            switch ($this->engine) {
                case self::MODE_MHASH:
                    $output = mhash($this->hash, $text, $this->computedKey);
                    break;
                case self::MODE_HASH:
                    $output = hash_hmac($this->hash, $text, $this->computedKey, true);
                    break;
                case self::MODE_INTERNAL:
                    $key    = str_pad($this->computedKey, $this->b, chr(0)); // step 1
                    $temp   = $this->ipad ^ $key;                            // step 2
                    $temp  .= $text;                                         // step 3
                    $temp   = call_user_func($this->hash, $temp);            // step 4
                    $output = $this->opad ^ $key;                            // step 5
                    $output.= $temp;                                         // step 6
                    $output = call_user_func($this->hash, $output);          // step 7
            }
        } else {
            switch ($this->engine) {
                case self::MODE_MHASH:
                    $output = mhash($this->hash, $text);
                    break;
                case self::MODE_HASH:
                    $output = hash($this->hash, $text, true);
                    break;
                case self::MODE_INTERNAL:
                    $output = call_user_func($this->hash, $text);
            }
        }

        return substr($output, 0, $this->l);
    }

    /**
     * Returns the hash length (in bytes)
     *
     * @access public
     * @return int
     */
    function getLength()
    {
        return $this->l;
    }

    /**
     * Wrapper for MD5
     *
     * @access private
     * @param string $m
     */
    function _md5($m)
    {
        return pack('H*', md5($m));
    }

    /**
     * Wrapper for SHA1
     *
     * @access private
     * @param string $m
     */
    function _sha1($m)
    {
        return pack('H*', sha1($m));
    }

    /**
     * Pure-PHP implementation of MD2
     *
     * See {@link http://tools.ietf.org/html/rfc1319 RFC1319}.
     *
     * @access private
     * @param string $m
     */
    function _md2($m)
    {
        static $s = array(
             41,  46,  67, 201, 162, 216, 124,   1,  61,  54,  84, 161, 236, 240, 6,
             19,  98, 167,   5, 243, 192, 199, 115, 140, 152, 147,  43, 217, 188,
             76, 130, 202,  30, 155,  87,  60, 253, 212, 224,  22, 103,  66, 111, 24,
            138,  23, 229,  18, 190,  78, 196, 214, 218, 158, 222,  73, 160, 251,
            245, 142, 187,  47, 238, 122, 169, 104, 121, 145,  21, 178,   7,  63,
            148, 194,  16, 137,  11,  34,  95,  33, 128, 127,  93, 154,  90, 144, 50,
             39,  53,  62, 204, 231, 191, 247, 151,   3, 255,  25,  48, 179,  72, 165,
            181, 209, 215,  94, 146,  42, 172,  86, 170, 198,  79, 184,  56, 210,
            150, 164, 125, 182, 118, 252, 107, 226, 156, 116,   4, 241,  69, 157,
            112,  89, 100, 113, 135,  32, 134,  91, 207, 101, 230,  45, 168,   2, 27,
             96,  37, 173, 174, 176, 185, 246,  28,  70,  97, 105,  52,  64, 126, 15,
             85,  71, 163,  35, 221,  81, 175,  58, 195,  92, 249, 206, 186, 197,
            234,  38,  44,  83,  13, 110, 133,  40, 132,   9, 211, 223, 205, 244, 65,
            129,  77,  82, 106, 220,  55, 200, 108, 193, 171, 250,  36, 225, 123,
              8,  12, 189, 177,  74, 120, 136, 149, 139, 227,  99, 232, 109, 233,
            203, 213, 254,  59,   0,  29,  57, 242, 239, 183,  14, 102,  88, 208, 228,
            166, 119, 114, 248, 235, 117,  75,  10,  49,  68,  80, 180, 143, 237,
             31,  26, 219, 153, 141,  51, 159,  17, 131, 20
        );

        // Step 1. Append Padding Bytes
        $pad = 16 - (strlen($m) & 0xF);
        $m.= str_repeat(chr($pad), $pad);

        $length = strlen($m);

        // Step 2. Append Checksum
        $c = str_repeat(chr(0), 16);
        $l = chr(0);
        for ($i = 0; $i < $length; $i+= 16) {
            for ($j = 0; $j < 16; $j++) {
                // RFC1319 incorrectly states that C[j] should be set to S[c xor L]
                //$c[$j] = chr($s[ord($m[$i + $j] ^ $l)]);
                // per <http://www.rfc-editor.org/errata_search.php?rfc=1319>, however, C[j] should be set to S[c xor L] xor C[j]
                $c[$j] = chr($s[ord($m[$i + $j] ^ $l)] ^ ord($c[$j]));
                $l = $c[$j];
            }
        }
        $m.= $c;

        $length+= 16;

        // Step 3. Initialize MD Buffer
        $x = str_repeat(chr(0), 48);

        // Step 4. Process Message in 16-Byte Blocks
        for ($i = 0; $i < $length; $i+= 16) {
            for ($j = 0; $j < 16; $j++) {
                $x[$j + 16] = $m[$i + $j];
                $x[$j + 32] = $x[$j + 16] ^ $x[$j];
            }
            $t = chr(0);
            for ($j = 0; $j < 18; $j++) {
                for ($k = 0; $k < 48; $k++) {
                    $x[$k] = $t = $x[$k] ^ chr($s[ord($t)]);
                    //$t = $x[$k] = $x[$k] ^ chr($s[ord($t)]);
                }
                $t = chr(ord($t) + $j);
            }
        }

        // Step 5. Output
        return substr($x, 0, 16);
    }

    /**
     * Pure-PHP implementation of SHA256
     *
     * See {@link http://en.wikipedia.org/wiki/SHA_hash_functions#SHA-256_.28a_SHA-2_variant.29_pseudocode SHA-256 (a SHA-2 variant) pseudocode - Wikipedia}.
     *
     * @access private
     * @param string $m
     */
    function _sha256($m)
    {
        if (extension_loaded('suhosin')) {
            return pack('H*', sha256($m));
        }

        // Initialize variables
        $hash = array(
            0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
        );
        // Initialize table of round constants
        // (first 32 bits of the fractional parts of the cube roots of the first 64 primes 2..311)
        static $k = array(
            0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
            0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
            0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
            0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
            0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
            0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
            0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
            0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
        );

        // Pre-processing
        $length = strlen($m);
        // to round to nearest 56 mod 64, we'll add 64 - (length + (64 - 56)) % 64
        $m.= str_repeat(chr(0), 64 - (($length + 8) & 0x3F));
        $m[$length] = chr(0x80);
        // we don't support hashing strings 512MB long
        $m.= pack('N2', 0, $length << 3);

        // Process the message in successive 512-bit chunks
        $chunks = str_split($m, 64);
        foreach ($chunks as $chunk) {
            $w = array();
            for ($i = 0; $i < 16; $i++) {
                extract(unpack('Ntemp', $this->_string_shift($chunk, 4)));
                $w[] = $temp;
            }

            // Extend the sixteen 32-bit words into sixty-four 32-bit words
            for ($i = 16; $i < 64; $i++) {
                // @codingStandardsIgnoreStart
                $s0 = $this->_rightRotate($w[$i - 15],  7) ^
                      $this->_rightRotate($w[$i - 15], 18) ^
                      $this->_rightShift( $w[$i - 15],  3);
                $s1 = $this->_rightRotate($w[$i - 2], 17) ^
                      $this->_rightRotate($w[$i - 2], 19) ^
                      $this->_rightShift( $w[$i - 2], 10);
                // @codingStandardsIgnoreEnd
                $w[$i] = $this->_add($w[$i - 16], $s0, $w[$i - 7], $s1);
            }

            // Initialize hash value for this chunk
            list($a, $b, $c, $d, $e, $f, $g, $h) = $hash;

            // Main loop
            for ($i = 0; $i < 64; $i++) {
                $s0 = $this->_rightRotate($a,  2) ^
                      $this->_rightRotate($a, 13) ^
                      $this->_rightRotate($a, 22);
                $maj = ($a & $b) ^
                       ($a & $c) ^
                       ($b & $c);
                $t2 = $this->_add($s0, $maj);

                $s1 = $this->_rightRotate($e,  6) ^
                      $this->_rightRotate($e, 11) ^
                      $this->_rightRotate($e, 25);
                $ch = ($e & $f) ^
                      ($this->_not($e) & $g);
                $t1 = $this->_add($h, $s1, $ch, $k[$i], $w[$i]);

                $h = $g;
                $g = $f;
                $f = $e;
                $e = $this->_add($d, $t1);
                $d = $c;
                $c = $b;
                $b = $a;
                $a = $this->_add($t1, $t2);
            }

            // Add this chunk's hash to result so far
            $hash = array(
                $this->_add($hash[0], $a),
                $this->_add($hash[1], $b),
                $this->_add($hash[2], $c),
                $this->_add($hash[3], $d),
                $this->_add($hash[4], $e),
                $this->_add($hash[5], $f),
                $this->_add($hash[6], $g),
                $this->_add($hash[7], $h)
            );
        }

        // Produce the final hash value (big-endian)
        return pack('N8', $hash[0], $hash[1], $hash[2], $hash[3], $hash[4], $hash[5], $hash[6], $hash[7]);
    }

    /**
     * Pure-PHP implementation of SHA384 and SHA512
     *
     * @access private
     * @param string $m
     */
    function _sha512($m)
    {
        static $init384, $init512, $k;

        if (!isset($k)) {
            // Initialize variables
            $init384 = array( // initial values for SHA384
                'cbbb9d5dc1059ed8', '629a292a367cd507', '9159015a3070dd17', '152fecd8f70e5939',
                '67332667ffc00b31', '8eb44a8768581511', 'db0c2e0d64f98fa7', '47b5481dbefa4fa4'
            );
            $init512 = array( // initial values for SHA512
                '6a09e667f3bcc908', 'bb67ae8584caa73b', '3c6ef372fe94f82b', 'a54ff53a5f1d36f1',
                '510e527fade682d1', '9b05688c2b3e6c1f', '1f83d9abfb41bd6b', '5be0cd19137e2179'
            );

            for ($i = 0; $i < 8; $i++) {
                $init384[$i] = new BigInteger($init384[$i], 16);
                $init384[$i]->setPrecision(64);
                $init512[$i] = new BigInteger($init512[$i], 16);
                $init512[$i]->setPrecision(64);
            }

            // Initialize table of round constants
            // (first 64 bits of the fractional parts of the cube roots of the first 80 primes 2..409)
            $k = array(
                '428a2f98d728ae22', '7137449123ef65cd', 'b5c0fbcfec4d3b2f', 'e9b5dba58189dbbc',
                '3956c25bf348b538', '59f111f1b605d019', '923f82a4af194f9b', 'ab1c5ed5da6d8118',
                'd807aa98a3030242', '12835b0145706fbe', '243185be4ee4b28c', '550c7dc3d5ffb4e2',
                '72be5d74f27b896f', '80deb1fe3b1696b1', '9bdc06a725c71235', 'c19bf174cf692694',
                'e49b69c19ef14ad2', 'efbe4786384f25e3', '0fc19dc68b8cd5b5', '240ca1cc77ac9c65',
                '2de92c6f592b0275', '4a7484aa6ea6e483', '5cb0a9dcbd41fbd4', '76f988da831153b5',
                '983e5152ee66dfab', 'a831c66d2db43210', 'b00327c898fb213f', 'bf597fc7beef0ee4',
                'c6e00bf33da88fc2', 'd5a79147930aa725', '06ca6351e003826f', '142929670a0e6e70',
                '27b70a8546d22ffc', '2e1b21385c26c926', '4d2c6dfc5ac42aed', '53380d139d95b3df',
                '650a73548baf63de', '766a0abb3c77b2a8', '81c2c92e47edaee6', '92722c851482353b',
                'a2bfe8a14cf10364', 'a81a664bbc423001', 'c24b8b70d0f89791', 'c76c51a30654be30',
                'd192e819d6ef5218', 'd69906245565a910', 'f40e35855771202a', '106aa07032bbd1b8',
                '19a4c116b8d2d0c8', '1e376c085141ab53', '2748774cdf8eeb99', '34b0bcb5e19b48a8',
                '391c0cb3c5c95a63', '4ed8aa4ae3418acb', '5b9cca4f7763e373', '682e6ff3d6b2b8a3',
                '748f82ee5defb2fc', '78a5636f43172f60', '84c87814a1f0ab72', '8cc702081a6439ec',
                '90befffa23631e28', 'a4506cebde82bde9', 'bef9a3f7b2c67915', 'c67178f2e372532b',
                'ca273eceea26619c', 'd186b8c721c0c207', 'eada7dd6cde0eb1e', 'f57d4f7fee6ed178',
                '06f067aa72176fba', '0a637dc5a2c898a6', '113f9804bef90dae', '1b710b35131c471b',
                '28db77f523047d84', '32caab7b40c72493', '3c9ebe0a15c9bebc', '431d67c49c100d4c',
                '4cc5d4becb3e42b6', '597f299cfc657e2a', '5fcb6fab3ad6faec', '6c44198c4a475817'
            );

            for ($i = 0; $i < 80; $i++) {
                $k[$i] = new BigInteger($k[$i], 16);
            }
        }

        $hash = $this->l == 48 ? $init384 : $init512;

        // Pre-processing
        $length = strlen($m);
        // to round to nearest 112 mod 128, we'll add 128 - (length + (128 - 112)) % 128
        $m.= str_repeat(chr(0), 128 - (($length + 16) & 0x7F));
        $m[$length] = chr(0x80);
        // we don't support hashing strings 512MB long
        $m.= pack('N4', 0, 0, 0, $length << 3);

        // Process the message in successive 1024-bit chunks
        $chunks = str_split($m, 128);
        foreach ($chunks as $chunk) {
            $w = array();
            for ($i = 0; $i < 16; $i++) {
                $temp = new BigInteger($this->_string_shift($chunk, 8), 256);
                $temp->setPrecision(64);
                $w[] = $temp;
            }

            // Extend the sixteen 32-bit words into eighty 32-bit words
            for ($i = 16; $i < 80; $i++) {
                $temp = array(
                          $w[$i - 15]->bitwise_rightRotate(1),
                          $w[$i - 15]->bitwise_rightRotate(8),
                          $w[$i - 15]->bitwise_rightShift(7)
                );
                $s0 = $temp[0]->bitwise_xor($temp[1]);
                $s0 = $s0->bitwise_xor($temp[2]);
                $temp = array(
                          $w[$i - 2]->bitwise_rightRotate(19),
                          $w[$i - 2]->bitwise_rightRotate(61),
                          $w[$i - 2]->bitwise_rightShift(6)
                );
                $s1 = $temp[0]->bitwise_xor($temp[1]);
                $s1 = $s1->bitwise_xor($temp[2]);
                $w[$i] = $w[$i - 16]->copy();
                $w[$i] = $w[$i]->add($s0);
                $w[$i] = $w[$i]->add($w[$i - 7]);
                $w[$i] = $w[$i]->add($s1);
            }

            // Initialize hash value for this chunk
            $a = $hash[0]->copy();
            $b = $hash[1]->copy();
            $c = $hash[2]->copy();
            $d = $hash[3]->copy();
            $e = $hash[4]->copy();
            $f = $hash[5]->copy();
            $g = $hash[6]->copy();
            $h = $hash[7]->copy();

            // Main loop
            for ($i = 0; $i < 80; $i++) {
                $temp = array(
                    $a->bitwise_rightRotate(28),
                    $a->bitwise_rightRotate(34),
                    $a->bitwise_rightRotate(39)
                );
                $s0 = $temp[0]->bitwise_xor($temp[1]);
                $s0 = $s0->bitwise_xor($temp[2]);
                $temp = array(
                    $a->bitwise_and($b),
                    $a->bitwise_and($c),
                    $b->bitwise_and($c)
                );
                $maj = $temp[0]->bitwise_xor($temp[1]);
                $maj = $maj->bitwise_xor($temp[2]);
                $t2 = $s0->add($maj);

                $temp = array(
                    $e->bitwise_rightRotate(14),
                    $e->bitwise_rightRotate(18),
                    $e->bitwise_rightRotate(41)
                );
                $s1 = $temp[0]->bitwise_xor($temp[1]);
                $s1 = $s1->bitwise_xor($temp[2]);
                $temp = array(
                    $e->bitwise_and($f),
                    $g->bitwise_and($e->bitwise_not())
                );
                $ch = $temp[0]->bitwise_xor($temp[1]);
                $t1 = $h->add($s1);
                $t1 = $t1->add($ch);
                $t1 = $t1->add($k[$i]);
                $t1 = $t1->add($w[$i]);

                $h = $g->copy();
                $g = $f->copy();
                $f = $e->copy();
                $e = $d->add($t1);
                $d = $c->copy();
                $c = $b->copy();
                $b = $a->copy();
                $a = $t1->add($t2);
            }

            // Add this chunk's hash to result so far
            $hash = array(
                $hash[0]->add($a),
                $hash[1]->add($b),
                $hash[2]->add($c),
                $hash[3]->add($d),
                $hash[4]->add($e),
                $hash[5]->add($f),
                $hash[6]->add($g),
                $hash[7]->add($h)
            );
        }

        // Produce the final hash value (big-endian)
        // (\phpseclib\Crypt\Hash::hash() trims the output for hashes but not for HMACs.  as such, we trim the output here)
        $temp = $hash[0]->toBytes() . $hash[1]->toBytes() . $hash[2]->toBytes() . $hash[3]->toBytes() .
                $hash[4]->toBytes() . $hash[5]->toBytes();
        if ($this->l != 48) {
            $temp.= $hash[6]->toBytes() . $hash[7]->toBytes();
        }

        return $temp;
    }

    /**
     * Right Rotate
     *
     * @access private
     * @param int $int
     * @param int $amt
     * @see self::_sha256()
     * @return int
     */
    function _rightRotate($int, $amt)
    {
        $invamt = 32 - $amt;
        $mask = (1 << $invamt) - 1;
        return (($int << $invamt) & 0xFFFFFFFF) | (($int >> $amt) & $mask);
    }

    /**
     * Right Shift
     *
     * @access private
     * @param int $int
     * @param int $amt
     * @see self::_sha256()
     * @return int
     */
    function _rightShift($int, $amt)
    {
        $mask = (1 << (32 - $amt)) - 1;
        return ($int >> $amt) & $mask;
    }

    /**
     * Not
     *
     * @access private
     * @param int $int
     * @see self::_sha256()
     * @return int
     */
    function _not($int)
    {
        return ~$int & 0xFFFFFFFF;
    }

    /**
     * Add
     *
     * _sha256() adds multiple unsigned 32-bit integers.  Since PHP doesn't support unsigned integers and since the
     * possibility of overflow exists, care has to be taken.  BigInteger could be used but this should be faster.
     *
     * @param int $...
     * @return int
     * @see self::_sha256()
     * @access private
     */
    function _add()
    {
        static $mod;
        if (!isset($mod)) {
            $mod = pow(2, 32);
        }

        $result = 0;
        $arguments = func_get_args();
        foreach ($arguments as $argument) {
            $result+= $argument < 0 ? ($argument & 0x7FFFFFFF) + 0x80000000 : $argument;
        }

        if ((php_uname('m') & "\xDF\xDF\xDF") != 'ARM') {
            return fmod($result, $mod);
        }

        return (fmod($result, 0x80000000) & 0x7FFFFFFF) |
            ((fmod(floor($result / 0x80000000), 2) & 1) << 31);
    }

    /**
     * String Shift
     *
     * Inspired by array_shift
     *
     * @param string $string
     * @param int $index
     * @return string
     * @access private
     */
    function _string_shift(&$string, $index = 1)
    {
        $substr = substr($string, 0, $index);
        $string = substr($string, $index);
        return $substr;
    }
}
