Blowfish.php

<?php

/**
 * Pure-PHP implementation of Blowfish.
 *
 * Uses an internal implementation.
 *
 * PHP version 5
 *
 * Useful resources are as follows:
 *
 *  - {@link http://en.wikipedia.org/wiki/Blowfish_(cipher) Wikipedia description of Blowfish}
 *
 * # An overview of bcrypt vs Blowfish
 *
 * OpenSSH private keys use a customized version of bcrypt. Specifically, instead of
 * encrypting OrpheanBeholderScryDoubt 64 times OpenSSH's bcrypt variant encrypts
 * OxychromaticBlowfishSwatDynamite 64 times. so we can't use crypt().
 *
 * bcrypt is basically Blowfish but instead of performing the key expansion once it performs
 * the expansion 129 times for each round, with the first key expansion interleaving the salt
 * and password. This renders OpenSSL unusable and forces us to use a pure-PHP implementation
 * of blowfish.
 *
 * # phpseclib's three different _encryptBlock() implementations
 *
 * When using Blowfish as an encryption algorithm, _encryptBlock() is called 9 + 512 +
 * (the number of blocks in the plaintext) times.
 *
 * Each of the first 9 calls to _encryptBlock() modify the P-array. Each of the next 512
 * calls modify the S-boxes. The remaining _encryptBlock() calls operate on the plaintext to
 * produce the ciphertext. In the pure-PHP implementation of Blowfish these remaining
 * _encryptBlock() calls are highly optimized through the use of eval(). Among other things,
 * P-array lookups are eliminated by hard-coding the key-dependent P-array values, and thus we
 * have explained 2 of the 4 different _encryptBlock() implementations.
 *
 * With bcrypt things are a bit different. _encryptBlock() is called 1,079,296 times,
 * assuming 16 rounds (which is what OpenSSH's bcrypt defaults to). The eval()-optimized
 * _encryptBlock() isn't as beneficial because the P-array values are not constant. Well, they
 * are constant, but only for, at most, 777 _encryptBlock() calls, which is equivalent to ~6KB
 * of data. The average length of back to back _encryptBlock() calls with a fixed P-array is
 * 514.12, which is ~4KB of data. Creating an eval()-optimized _encryptBlock() has an upfront
 * cost, which is CPU dependent and is probably not going to be worth it for just ~4KB of
 * data. Conseqeuently, bcrypt does not benefit from the eval()-optimized _encryptBlock().
 *
 * The regular _encryptBlock() does unpack() and pack() on every call, as well, and that can
 * begin to add up after one million function calls.
 *
 * In theory, one might think that it might be beneficial to rewrite all block ciphers so
 * that, instead of passing strings to _encryptBlock(), you convert the string to an array of
 * integers and then pass successive subarrays of that array to _encryptBlock. This, however,
 * kills PHP's memory use. Like let's say you have a 1MB long string. After doing
 * $in = str_repeat('a', 1024 * 1024); PHP's memory utilization jumps up by ~1MB. After doing
 * $blocks = str_split($in, 4); it jumps up by an additional ~16MB. After
 * $blocks = array_map(fn($x) => unpack('N*', $x), $blocks); it jumps up by an additional
 * ~90MB, yielding a 106x increase in memory usage. Consequently, it bcrypt calls a different
 * _encryptBlock() then the regular Blowfish does. That said, the Blowfish _encryptBlock() is
 * basically just a thin wrapper around the bcrypt _encryptBlock(), so there's that.
 *
 * # phpseclib's three different _setupKey() implementations
 *
 * Every bcrypt round is the equivalent of encrypting 512KB of data. Since OpenSSH uses 16
 * rounds by default that's ~8MB of data that's essentially being encrypted whenever
 * you use bcrypt. That's a lot of data, however, bcrypt operates within tighter constraints
 * than regular Blowfish, so we can use that to our advantage. In particular, whereas Blowfish
 * supports variable length keys, in bcrypt, the initial "key" is the sha512 hash of the
 * password. sha512 hashes are 512 bits or 64 bytes long and thus the bcrypt keys are of a
 * fixed length whereas Blowfish keys are not of a fixed length.
 *
 * bcrypt actually has two different key expansion steps. The first one (expandstate) is
 * constantly XOR'ing every _encryptBlock() parameter against the salt prior _encryptBlock()'s
 * being called. The second one (expand0state) is more similar to Blowfish's _setupKey()
 * but it can still use the fixed length key optimization discussed above and can do away with
 * the pack() / unpack() calls.
 *
 * I suppose _setupKey() could be made to be a thin wrapper around expandstate() but idk it's
 * just a lot of work for very marginal benefits as _setupKey() is only called once for
 * regular Blowfish vs the 128 times it's called --per round-- with bcrypt.
 *
 * # blowfish + bcrypt in the same class
 *
 * Altho there's a lot of Blowfish code that bcrypt doesn't re-use, bcrypt does re-use the
 * initial S-boxes, the initial P-array and the int-only _encryptBlock() implementation.
 *
 * # Credit
 *
 * phpseclib's bcrypt implementation is based losely off of OpenSSH's implementation:
 *
 * https://github.com/openssh/openssh-portable/blob/master/openbsd-compat/bcrypt_pbkdf.c
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $blowfish = new \phpseclib3\Crypt\Blowfish('ctr');
 *
 *    $blowfish->setKey('12345678901234567890123456789012');
 *
 *    $plaintext = str_repeat('a', 1024);
 *
 *    echo $blowfish->decrypt($blowfish->encrypt($plaintext));
 * ?>
 * </code>
 *
 * @author    Jim Wigginton <terrafrost@php.net>
 * @author    Hans-Juergen Petrich <petrich@tronic-media.com>
 * @copyright 2007 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

declare(strict_types=1);

namespace phpseclib3\Crypt;

use phpseclib3\Crypt\Common\BlockCipher;
use phpseclib3\Exception\InvalidArgumentException;
use phpseclib3\Exception\LengthException;

/**
 * Pure-PHP implementation of Blowfish.
 *
 * @author  Jim Wigginton <terrafrost@php.net>
 * @author  Hans-Juergen Petrich <petrich@tronic-media.com>
 */
class Blowfish extends BlockCipher
{
    /**
     * Block Length of the cipher
     *
     * @see \phpseclib3\Crypt\Common\SymmetricKey::block_size
     * @var int
     */
    protected $block_size = 8;

    /**
     * The fixed subkeys boxes ($sbox0 - $sbox3) with 256 entries each
     *
     * S-Box 0
     *
     * @var    array
     */
    private static $sbox0 = [
        0xd1310ba6, 0x98dfb5ac, 0x2ffd72db, 0xd01adfb7, 0xb8e1afed, 0x6a267e96, 0xba7c9045, 0xf12c7f99,
        0x24a19947, 0xb3916cf7, 0x0801f2e2, 0x858efc16, 0x636920d8, 0x71574e69, 0xa458fea3, 0xf4933d7e,
        0x0d95748f, 0x728eb658, 0x718bcd58, 0x82154aee, 0x7b54a41d, 0xc25a59b5, 0x9c30d539, 0x2af26013,
        0xc5d1b023, 0x286085f0, 0xca417918, 0xb8db38ef, 0x8e79dcb0, 0x603a180e, 0x6c9e0e8b, 0xb01e8a3e,
        0xd71577c1, 0xbd314b27, 0x78af2fda, 0x55605c60, 0xe65525f3, 0xaa55ab94, 0x57489862, 0x63e81440,
        0x55ca396a, 0x2aab10b6, 0xb4cc5c34, 0x1141e8ce, 0xa15486af, 0x7c72e993, 0xb3ee1411, 0x636fbc2a,
        0x2ba9c55d, 0x741831f6, 0xce5c3e16, 0x9b87931e, 0xafd6ba33, 0x6c24cf5c, 0x7a325381, 0x28958677,
        0x3b8f4898, 0x6b4bb9af, 0xc4bfe81b, 0x66282193, 0x61d809cc, 0xfb21a991, 0x487cac60, 0x5dec8032,
        0xef845d5d, 0xe98575b1, 0xdc262302, 0xeb651b88, 0x23893e81, 0xd396acc5, 0x0f6d6ff3, 0x83f44239,
        0x2e0b4482, 0xa4842004, 0x69c8f04a, 0x9e1f9b5e, 0x21c66842, 0xf6e96c9a, 0x670c9c61, 0xabd388f0,
        0x6a51a0d2, 0xd8542f68, 0x960fa728, 0xab5133a3, 0x6eef0b6c, 0x137a3be4, 0xba3bf050, 0x7efb2a98,
        0xa1f1651d, 0x39af0176, 0x66ca593e, 0x82430e88, 0x8cee8619, 0x456f9fb4, 0x7d84a5c3, 0x3b8b5ebe,
        0xe06f75d8, 0x85c12073, 0x401a449f, 0x56c16aa6, 0x4ed3aa62, 0x363f7706, 0x1bfedf72, 0x429b023d,
        0x37d0d724, 0xd00a1248, 0xdb0fead3, 0x49f1c09b, 0x075372c9, 0x80991b7b, 0x25d479d8, 0xf6e8def7,
        0xe3fe501a, 0xb6794c3b, 0x976ce0bd, 0x04c006ba, 0xc1a94fb6, 0x409f60c4, 0x5e5c9ec2, 0x196a2463,
        0x68fb6faf, 0x3e6c53b5, 0x1339b2eb, 0x3b52ec6f, 0x6dfc511f, 0x9b30952c, 0xcc814544, 0xaf5ebd09,
        0xbee3d004, 0xde334afd, 0x660f2807, 0x192e4bb3, 0xc0cba857, 0x45c8740f, 0xd20b5f39, 0xb9d3fbdb,
        0x5579c0bd, 0x1a60320a, 0xd6a100c6, 0x402c7279, 0x679f25fe, 0xfb1fa3cc, 0x8ea5e9f8, 0xdb3222f8,
        0x3c7516df, 0xfd616b15, 0x2f501ec8, 0xad0552ab, 0x323db5fa, 0xfd238760, 0x53317b48, 0x3e00df82,
        0x9e5c57bb, 0xca6f8ca0, 0x1a87562e, 0xdf1769db, 0xd542a8f6, 0x287effc3, 0xac6732c6, 0x8c4f5573,
        0x695b27b0, 0xbbca58c8, 0xe1ffa35d, 0xb8f011a0, 0x10fa3d98, 0xfd2183b8, 0x4afcb56c, 0x2dd1d35b,
        0x9a53e479, 0xb6f84565, 0xd28e49bc, 0x4bfb9790, 0xe1ddf2da, 0xa4cb7e33, 0x62fb1341, 0xcee4c6e8,
        0xef20cada, 0x36774c01, 0xd07e9efe, 0x2bf11fb4, 0x95dbda4d, 0xae909198, 0xeaad8e71, 0x6b93d5a0,
        0xd08ed1d0, 0xafc725e0, 0x8e3c5b2f, 0x8e7594b7, 0x8ff6e2fb, 0xf2122b64, 0x8888b812, 0x900df01c,
        0x4fad5ea0, 0x688fc31c, 0xd1cff191, 0xb3a8c1ad, 0x2f2f2218, 0xbe0e1777, 0xea752dfe, 0x8b021fa1,
        0xe5a0cc0f, 0xb56f74e8, 0x18acf3d6, 0xce89e299, 0xb4a84fe0, 0xfd13e0b7, 0x7cc43b81, 0xd2ada8d9,
        0x165fa266, 0x80957705, 0x93cc7314, 0x211a1477, 0xe6ad2065, 0x77b5fa86, 0xc75442f5, 0xfb9d35cf,
        0xebcdaf0c, 0x7b3e89a0, 0xd6411bd3, 0xae1e7e49, 0x00250e2d, 0x2071b35e, 0x226800bb, 0x57b8e0af,
        0x2464369b, 0xf009b91e, 0x5563911d, 0x59dfa6aa, 0x78c14389, 0xd95a537f, 0x207d5ba2, 0x02e5b9c5,
        0x83260376, 0x6295cfa9, 0x11c81968, 0x4e734a41, 0xb3472dca, 0x7b14a94a, 0x1b510052, 0x9a532915,
        0xd60f573f, 0xbc9bc6e4, 0x2b60a476, 0x81e67400, 0x08ba6fb5, 0x571be91f, 0xf296ec6b, 0x2a0dd915,
        0xb6636521, 0xe7b9f9b6, 0xff34052e, 0xc5855664, 0x53b02d5d, 0xa99f8fa1, 0x08ba4799, 0x6e85076a,
    ];

    /**
     * S-Box 1
     *
     * @var    array
     */
    private static $sbox1 = [
        0x4b7a70e9, 0xb5b32944, 0xdb75092e, 0xc4192623, 0xad6ea6b0, 0x49a7df7d, 0x9cee60b8, 0x8fedb266,
        0xecaa8c71, 0x699a17ff, 0x5664526c, 0xc2b19ee1, 0x193602a5, 0x75094c29, 0xa0591340, 0xe4183a3e,
        0x3f54989a, 0x5b429d65, 0x6b8fe4d6, 0x99f73fd6, 0xa1d29c07, 0xefe830f5, 0x4d2d38e6, 0xf0255dc1,
        0x4cdd2086, 0x8470eb26, 0x6382e9c6, 0x021ecc5e, 0x09686b3f, 0x3ebaefc9, 0x3c971814, 0x6b6a70a1,
        0x687f3584, 0x52a0e286, 0xb79c5305, 0xaa500737, 0x3e07841c, 0x7fdeae5c, 0x8e7d44ec, 0x5716f2b8,
        0xb03ada37, 0xf0500c0d, 0xf01c1f04, 0x0200b3ff, 0xae0cf51a, 0x3cb574b2, 0x25837a58, 0xdc0921bd,
        0xd19113f9, 0x7ca92ff6, 0x94324773, 0x22f54701, 0x3ae5e581, 0x37c2dadc, 0xc8b57634, 0x9af3dda7,
        0xa9446146, 0x0fd0030e, 0xecc8c73e, 0xa4751e41, 0xe238cd99, 0x3bea0e2f, 0x3280bba1, 0x183eb331,
        0x4e548b38, 0x4f6db908, 0x6f420d03, 0xf60a04bf, 0x2cb81290, 0x24977c79, 0x5679b072, 0xbcaf89af,
        0xde9a771f, 0xd9930810, 0xb38bae12, 0xdccf3f2e, 0x5512721f, 0x2e6b7124, 0x501adde6, 0x9f84cd87,
        0x7a584718, 0x7408da17, 0xbc9f9abc, 0xe94b7d8c, 0xec7aec3a, 0xdb851dfa, 0x63094366, 0xc464c3d2,
        0xef1c1847, 0x3215d908, 0xdd433b37, 0x24c2ba16, 0x12a14d43, 0x2a65c451, 0x50940002, 0x133ae4dd,
        0x71dff89e, 0x10314e55, 0x81ac77d6, 0x5f11199b, 0x043556f1, 0xd7a3c76b, 0x3c11183b, 0x5924a509,
        0xf28fe6ed, 0x97f1fbfa, 0x9ebabf2c, 0x1e153c6e, 0x86e34570, 0xeae96fb1, 0x860e5e0a, 0x5a3e2ab3,
        0x771fe71c, 0x4e3d06fa, 0x2965dcb9, 0x99e71d0f, 0x803e89d6, 0x5266c825, 0x2e4cc978, 0x9c10b36a,
        0xc6150eba, 0x94e2ea78, 0xa5fc3c53, 0x1e0a2df4, 0xf2f74ea7, 0x361d2b3d, 0x1939260f, 0x19c27960,
        0x5223a708, 0xf71312b6, 0xebadfe6e, 0xeac31f66, 0xe3bc4595, 0xa67bc883, 0xb17f37d1, 0x018cff28,
        0xc332ddef, 0xbe6c5aa5, 0x65582185, 0x68ab9802, 0xeecea50f, 0xdb2f953b, 0x2aef7dad, 0x5b6e2f84,
        0x1521b628, 0x29076170, 0xecdd4775, 0x619f1510, 0x13cca830, 0xeb61bd96, 0x0334fe1e, 0xaa0363cf,
        0xb5735c90, 0x4c70a239, 0xd59e9e0b, 0xcbaade14, 0xeecc86bc, 0x60622ca7, 0x9cab5cab, 0xb2f3846e,
        0x648b1eaf, 0x19bdf0ca, 0xa02369b9, 0x655abb50, 0x40685a32, 0x3c2ab4b3, 0x319ee9d5, 0xc021b8f7,
        0x9b540b19, 0x875fa099, 0x95f7997e, 0x623d7da8, 0xf837889a, 0x97e32d77, 0x11ed935f, 0x16681281,
        0x0e358829, 0xc7e61fd6, 0x96dedfa1, 0x7858ba99, 0x57f584a5, 0x1b227263, 0x9b83c3ff, 0x1ac24696,
        0xcdb30aeb, 0x532e3054, 0x8fd948e4, 0x6dbc3128, 0x58ebf2ef, 0x34c6ffea, 0xfe28ed61, 0xee7c3c73,
        0x5d4a14d9, 0xe864b7e3, 0x42105d14, 0x203e13e0, 0x45eee2b6, 0xa3aaabea, 0xdb6c4f15, 0xfacb4fd0,
        0xc742f442, 0xef6abbb5, 0x654f3b1d, 0x41cd2105, 0xd81e799e, 0x86854dc7, 0xe44b476a, 0x3d816250,
        0xcf62a1f2, 0x5b8d2646, 0xfc8883a0, 0xc1c7b6a3, 0x7f1524c3, 0x69cb7492, 0x47848a0b, 0x5692b285,
        0x095bbf00, 0xad19489d, 0x1462b174, 0x23820e00, 0x58428d2a, 0x0c55f5ea, 0x1dadf43e, 0x233f7061,
        0x3372f092, 0x8d937e41, 0xd65fecf1, 0x6c223bdb, 0x7cde3759, 0xcbee7460, 0x4085f2a7, 0xce77326e,
        0xa6078084, 0x19f8509e, 0xe8efd855, 0x61d99735, 0xa969a7aa, 0xc50c06c2, 0x5a04abfc, 0x800bcadc,
        0x9e447a2e, 0xc3453484, 0xfdd56705, 0x0e1e9ec9, 0xdb73dbd3, 0x105588cd, 0x675fda79, 0xe3674340,
        0xc5c43465, 0x713e38d8, 0x3d28f89e, 0xf16dff20, 0x153e21e7, 0x8fb03d4a, 0xe6e39f2b, 0xdb83adf7,
    ];

    /**
     * S-Box 2
     *
     * @var    array
     */
    private static $sbox2 = [
        0xe93d5a68, 0x948140f7, 0xf64c261c, 0x94692934, 0x411520f7, 0x7602d4f7, 0xbcf46b2e, 0xd4a20068,
        0xd4082471, 0x3320f46a, 0x43b7d4b7, 0x500061af, 0x1e39f62e, 0x97244546, 0x14214f74, 0xbf8b8840,
        0x4d95fc1d, 0x96b591af, 0x70f4ddd3, 0x66a02f45, 0xbfbc09ec, 0x03bd9785, 0x7fac6dd0, 0x31cb8504,
        0x96eb27b3, 0x55fd3941, 0xda2547e6, 0xabca0a9a, 0x28507825, 0x530429f4, 0x0a2c86da, 0xe9b66dfb,
        0x68dc1462, 0xd7486900, 0x680ec0a4, 0x27a18dee, 0x4f3ffea2, 0xe887ad8c, 0xb58ce006, 0x7af4d6b6,
        0xaace1e7c, 0xd3375fec, 0xce78a399, 0x406b2a42, 0x20fe9e35, 0xd9f385b9, 0xee39d7ab, 0x3b124e8b,
        0x1dc9faf7, 0x4b6d1856, 0x26a36631, 0xeae397b2, 0x3a6efa74, 0xdd5b4332, 0x6841e7f7, 0xca7820fb,
        0xfb0af54e, 0xd8feb397, 0x454056ac, 0xba489527, 0x55533a3a, 0x20838d87, 0xfe6ba9b7, 0xd096954b,
        0x55a867bc, 0xa1159a58, 0xcca92963, 0x99e1db33, 0xa62a4a56, 0x3f3125f9, 0x5ef47e1c, 0x9029317c,
        0xfdf8e802, 0x04272f70, 0x80bb155c, 0x05282ce3, 0x95c11548, 0xe4c66d22, 0x48c1133f, 0xc70f86dc,
        0x07f9c9ee, 0x41041f0f, 0x404779a4, 0x5d886e17, 0x325f51eb, 0xd59bc0d1, 0xf2bcc18f, 0x41113564,
        0x257b7834, 0x602a9c60, 0xdff8e8a3, 0x1f636c1b, 0x0e12b4c2, 0x02e1329e, 0xaf664fd1, 0xcad18115,
        0x6b2395e0, 0x333e92e1, 0x3b240b62, 0xeebeb922, 0x85b2a20e, 0xe6ba0d99, 0xde720c8c, 0x2da2f728,
        0xd0127845, 0x95b794fd, 0x647d0862, 0xe7ccf5f0, 0x5449a36f, 0x877d48fa, 0xc39dfd27, 0xf33e8d1e,
        0x0a476341, 0x992eff74, 0x3a6f6eab, 0xf4f8fd37, 0xa812dc60, 0xa1ebddf8, 0x991be14c, 0xdb6e6b0d,
        0xc67b5510, 0x6d672c37, 0x2765d43b, 0xdcd0e804, 0xf1290dc7, 0xcc00ffa3, 0xb5390f92, 0x690fed0b,
        0x667b9ffb, 0xcedb7d9c, 0xa091cf0b, 0xd9155ea3, 0xbb132f88, 0x515bad24, 0x7b9479bf, 0x763bd6eb,
        0x37392eb3, 0xcc115979, 0x8026e297, 0xf42e312d, 0x6842ada7, 0xc66a2b3b, 0x12754ccc, 0x782ef11c,
        0x6a124237, 0xb79251e7, 0x06a1bbe6, 0x4bfb6350, 0x1a6b1018, 0x11caedfa, 0x3d25bdd8, 0xe2e1c3c9,
        0x44421659, 0x0a121386, 0xd90cec6e, 0xd5abea2a, 0x64af674e, 0xda86a85f, 0xbebfe988, 0x64e4c3fe,
        0x9dbc8057, 0xf0f7c086, 0x60787bf8, 0x6003604d, 0xd1fd8346, 0xf6381fb0, 0x7745ae04, 0xd736fccc,
        0x83426b33, 0xf01eab71, 0xb0804187, 0x3c005e5f, 0x77a057be, 0xbde8ae24, 0x55464299, 0xbf582e61,
        0x4e58f48f, 0xf2ddfda2, 0xf474ef38, 0x8789bdc2, 0x5366f9c3, 0xc8b38e74, 0xb475f255, 0x46fcd9b9,
        0x7aeb2661, 0x8b1ddf84, 0x846a0e79, 0x915f95e2, 0x466e598e, 0x20b45770, 0x8cd55591, 0xc902de4c,
        0xb90bace1, 0xbb8205d0, 0x11a86248, 0x7574a99e, 0xb77f19b6, 0xe0a9dc09, 0x662d09a1, 0xc4324633,
        0xe85a1f02, 0x09f0be8c, 0x4a99a025, 0x1d6efe10, 0x1ab93d1d, 0x0ba5a4df, 0xa186f20f, 0x2868f169,
        0xdcb7da83, 0x573906fe, 0xa1e2ce9b, 0x4fcd7f52, 0x50115e01, 0xa70683fa, 0xa002b5c4, 0x0de6d027,
        0x9af88c27, 0x773f8641, 0xc3604c06, 0x61a806b5, 0xf0177a28, 0xc0f586e0, 0x006058aa, 0x30dc7d62,
        0x11e69ed7, 0x2338ea63, 0x53c2dd94, 0xc2c21634, 0xbbcbee56, 0x90bcb6de, 0xebfc7da1, 0xce591d76,
        0x6f05e409, 0x4b7c0188, 0x39720a3d, 0x7c927c24, 0x86e3725f, 0x724d9db9, 0x1ac15bb4, 0xd39eb8fc,
        0xed545578, 0x08fca5b5, 0xd83d7cd3, 0x4dad0fc4, 0x1e50ef5e, 0xb161e6f8, 0xa28514d9, 0x6c51133c,
        0x6fd5c7e7, 0x56e14ec4, 0x362abfce, 0xddc6c837, 0xd79a3234, 0x92638212, 0x670efa8e, 0x406000e0,
    ];

    /**
     * S-Box 3
     *
     * @var    array
     */
    private static $sbox3 = [
        0x3a39ce37, 0xd3faf5cf, 0xabc27737, 0x5ac52d1b, 0x5cb0679e, 0x4fa33742, 0xd3822740, 0x99bc9bbe,
        0xd5118e9d, 0xbf0f7315, 0xd62d1c7e, 0xc700c47b, 0xb78c1b6b, 0x21a19045, 0xb26eb1be, 0x6a366eb4,
        0x5748ab2f, 0xbc946e79, 0xc6a376d2, 0x6549c2c8, 0x530ff8ee, 0x468dde7d, 0xd5730a1d, 0x4cd04dc6,
        0x2939bbdb, 0xa9ba4650, 0xac9526e8, 0xbe5ee304, 0xa1fad5f0, 0x6a2d519a, 0x63ef8ce2, 0x9a86ee22,
        0xc089c2b8, 0x43242ef6, 0xa51e03aa, 0x9cf2d0a4, 0x83c061ba, 0x9be96a4d, 0x8fe51550, 0xba645bd6,
        0x2826a2f9, 0xa73a3ae1, 0x4ba99586, 0xef5562e9, 0xc72fefd3, 0xf752f7da, 0x3f046f69, 0x77fa0a59,
        0x80e4a915, 0x87b08601, 0x9b09e6ad, 0x3b3ee593, 0xe990fd5a, 0x9e34d797, 0x2cf0b7d9, 0x022b8b51,
        0x96d5ac3a, 0x017da67d, 0xd1cf3ed6, 0x7c7d2d28, 0x1f9f25cf, 0xadf2b89b, 0x5ad6b472, 0x5a88f54c,
        0xe029ac71, 0xe019a5e6, 0x47b0acfd, 0xed93fa9b, 0xe8d3c48d, 0x283b57cc, 0xf8d56629, 0x79132e28,
        0x785f0191, 0xed756055, 0xf7960e44, 0xe3d35e8c, 0x15056dd4, 0x88f46dba, 0x03a16125, 0x0564f0bd,
        0xc3eb9e15, 0x3c9057a2, 0x97271aec, 0xa93a072a, 0x1b3f6d9b, 0x1e6321f5, 0xf59c66fb, 0x26dcf319,
        0x7533d928, 0xb155fdf5, 0x03563482, 0x8aba3cbb, 0x28517711, 0xc20ad9f8, 0xabcc5167, 0xccad925f,
        0x4de81751, 0x3830dc8e, 0x379d5862, 0x9320f991, 0xea7a90c2, 0xfb3e7bce, 0x5121ce64, 0x774fbe32,
        0xa8b6e37e, 0xc3293d46, 0x48de5369, 0x6413e680, 0xa2ae0810, 0xdd6db224, 0x69852dfd, 0x09072166,
        0xb39a460a, 0x6445c0dd, 0x586cdecf, 0x1c20c8ae, 0x5bbef7dd, 0x1b588d40, 0xccd2017f, 0x6bb4e3bb,
        0xdda26a7e, 0x3a59ff45, 0x3e350a44, 0xbcb4cdd5, 0x72eacea8, 0xfa6484bb, 0x8d6612ae, 0xbf3c6f47,
        0xd29be463, 0x542f5d9e, 0xaec2771b, 0xf64e6370, 0x740e0d8d, 0xe75b1357, 0xf8721671, 0xaf537d5d,
        0x4040cb08, 0x4eb4e2cc, 0x34d2466a, 0x0115af84, 0xe1b00428, 0x95983a1d, 0x06b89fb4, 0xce6ea048,
        0x6f3f3b82, 0x3520ab82, 0x011a1d4b, 0x277227f8, 0x611560b1, 0xe7933fdc, 0xbb3a792b, 0x344525bd,
        0xa08839e1, 0x51ce794b, 0x2f32c9b7, 0xa01fbac9, 0xe01cc87e, 0xbcc7d1f6, 0xcf0111c3, 0xa1e8aac7,
        0x1a908749, 0xd44fbd9a, 0xd0dadecb, 0xd50ada38, 0x0339c32a, 0xc6913667, 0x8df9317c, 0xe0b12b4f,
        0xf79e59b7, 0x43f5bb3a, 0xf2d519ff, 0x27d9459c, 0xbf97222c, 0x15e6fc2a, 0x0f91fc71, 0x9b941525,
        0xfae59361, 0xceb69ceb, 0xc2a86459, 0x12baa8d1, 0xb6c1075e, 0xe3056a0c, 0x10d25065, 0xcb03a442,
        0xe0ec6e0e, 0x1698db3b, 0x4c98a0be, 0x3278e964, 0x9f1f9532, 0xe0d392df, 0xd3a0342b, 0x8971f21e,
        0x1b0a7441, 0x4ba3348c, 0xc5be7120, 0xc37632d8, 0xdf359f8d, 0x9b992f2e, 0xe60b6f47, 0x0fe3f11d,
        0xe54cda54, 0x1edad891, 0xce6279cf, 0xcd3e7e6f, 0x1618b166, 0xfd2c1d05, 0x848fd2c5, 0xf6fb2299,
        0xf523f357, 0xa6327623, 0x93a83531, 0x56cccd02, 0xacf08162, 0x5a75ebb5, 0x6e163697, 0x88d273cc,
        0xde966292, 0x81b949d0, 0x4c50901b, 0x71c65614, 0xe6c6c7bd, 0x327a140a, 0x45e1d006, 0xc3f27b9a,
        0xc9aa53fd, 0x62a80f00, 0xbb25bfe2, 0x35bdd2f6, 0x71126905, 0xb2040222, 0xb6cbcf7c, 0xcd769c2b,
        0x53113ec0, 0x1640e3d3, 0x38abbd60, 0x2547adf0, 0xba38209c, 0xf746ce76, 0x77afa1c5, 0x20756060,
        0x85cbfe4e, 0x8ae88dd8, 0x7aaaf9b0, 0x4cf9aa7e, 0x1948c25c, 0x02fb8a8c, 0x01c36ae4, 0xd6ebe1f9,
        0x90d4f869, 0xa65cdea0, 0x3f09252d, 0xc208e69f, 0xb74e6132, 0xce77e25b, 0x578fdfe3, 0x3ac372e6,
    ];

    /**
     * P-Array consists of 18 32-bit subkeys
     *
     * @var array
     */
    private static $parray = [
        0x243f6a88, 0x85a308d3, 0x13198a2e, 0x03707344, 0xa4093822, 0x299f31d0,
        0x082efa98, 0xec4e6c89, 0x452821e6, 0x38d01377, 0xbe5466cf, 0x34e90c6c,
        0xc0ac29b7, 0xc97c50dd, 0x3f84d5b5, 0xb5470917, 0x9216d5d9, 0x8979fb1b,
    ];

    /**
     * The BCTX-working Array
     *
     * Holds the expanded key [p] and the key-depended s-boxes [sb]
     *
     * @var array
     */
    private $bctx;

    /**
     * Holds the last used key
     *
     * @var array
     */
    private $kl;

    /**
     * The Key Length (in bytes)
     * {@internal The max value is 256 / 8 = 32, the min value is 128 / 8 = 16.  Exists in conjunction with $Nk
     *    because the encryption / decryption / key schedule creation requires this number and not $key_length.  We could
     *    derive this from $key_length or vice versa, but that'd mean we'd have to do multiple shift operations, so in lieu
     *    of that, we'll just precompute it once.}
     *
     * @see \phpseclib3\Crypt\Common\SymmetricKey::setKeyLength()
     * @var int
     */
    protected $key_length = 16;

    /**
     * Default Constructor.
     *
     * @throws InvalidArgumentException if an invalid / unsupported mode is provided
     */
    public function __construct(string $mode)
    {
        parent::__construct($mode);

        if ($this->mode == self::MODE_STREAM) {
            throw new InvalidArgumentException('Block ciphers cannot be ran in stream mode');
        }
    }

    /**
     * Sets the key length.
     *
     * Key lengths can be between 32 and 448 bits.
     */
    public function setKeyLength(int $length): void
    {
        if ($length < 32 || $length > 448) {
                throw new LengthException('Key size of ' . $length . ' bits is not supported by this algorithm. Only keys of sizes between 32 and 448 bits are supported');
        }

        $this->key_length = $length >> 3;

        parent::setKeyLength($length);
    }

    /**
     * Test for engine validity
     *
     * This is mainly just a wrapper to set things up for \phpseclib3\Crypt\Common\SymmetricKey::isValidEngine()
     *
     * @see \phpseclib3\Crypt\Common\SymmetricKey::isValidEngine()
     */
    protected function isValidEngineHelper(int $engine): bool
    {
        if ($engine == self::ENGINE_OPENSSL) {
            if ($this->key_length < 16) {
                return false;
            }
            // quoting https://www.openssl.org/news/openssl-3.0-notes.html, OpenSSL 3.0.1
            // "Moved all variations of the EVP ciphers CAST5, BF, IDEA, SEED, RC2, RC4, RC5, and DES to the legacy provider"
            // in theory openssl_get_cipher_methods() should catch this but, on GitHub Actions, at least, it does not
            if (defined('OPENSSL_VERSION_TEXT') && version_compare(preg_replace('#OpenSSL (\d+\.\d+\.\d+) .*#', '$1', OPENSSL_VERSION_TEXT), '3.0.1', '>=')) {
                return false;
            }
            $this->cipher_name_openssl_ecb = 'bf-ecb';
            $this->cipher_name_openssl = 'bf-' . $this->openssl_translate_mode();
        }

        return parent::isValidEngineHelper($engine);
    }

    /**
     * Setup the key (expansion)
     *
     * @see \phpseclib3\Crypt\Common\SymmetricKey::_setupKey()
     */
    protected function setupKey(): void
    {
        if (isset($this->kl['key']) && $this->key === $this->kl['key']) {
            // already expanded
            return;
        }
        $this->kl = ['key' => $this->key];

        /* key-expanding p[] and S-Box building sb[] */
        $this->bctx = [
            'p'  => [],
            'sb' => [
                self::$sbox0,
                self::$sbox1,
                self::$sbox2,
                self::$sbox3,
            ],
        ];

        // unpack binary string in unsigned chars
        $key  = array_values(unpack('C*', $this->key));
        $keyl = count($key);
        // with bcrypt $keyl will always be 16 (because the key is the sha512 of the key you provide)
        for ($j = 0, $i = 0; $i < 18; ++$i) {
            // xor P1 with the first 32-bits of the key, xor P2 with the second 32-bits ...
            for ($data = 0, $k = 0; $k < 4; ++$k) {
                $data = ($data << 8) | $key[$j];
                if (++$j >= $keyl) {
                    $j = 0;
                }
            }
            $this->bctx['p'][] = self::$parray[$i] ^ intval($data);
        }

        // encrypt the zero-string, replace P1 and P2 with the encrypted data,
        // encrypt P3 and P4 with the new P1 and P2, do it with all P-array and subkeys
        $data = "\0\0\0\0\0\0\0\0";
        for ($i = 0; $i < 18; $i += 2) {
            [$l, $r] = array_values(unpack('N*', $data = $this->encryptBlock($data)));
            $this->bctx['p'][$i    ] = $l;
            $this->bctx['p'][$i + 1] = $r;
        }
        for ($i = 0; $i < 4; ++$i) {
            for ($j = 0; $j < 256; $j += 2) {
                [$l, $r] = array_values(unpack('N*', $data = $this->encryptBlock($data)));
                $this->bctx['sb'][$i][$j    ] = $l;
                $this->bctx['sb'][$i][$j + 1] = $r;
            }
        }
    }

    /**
     * Initialize Static Variables
     */
    protected static function initialize_static_variables(): void
    {
        if (is_float(self::$sbox2[0])) {
            self::$sbox0 = array_map('intval', self::$sbox0);
            self::$sbox1 = array_map('intval', self::$sbox1);
            self::$sbox2 = array_map('intval', self::$sbox2);
            self::$sbox3 = array_map('intval', self::$sbox3);
            self::$parray = array_map('intval', self::$parray);
        }

        parent::initialize_static_variables();
    }

    /**
     * bcrypt
     */
    private static function bcrypt_hash(string $sha2pass, string $sha2salt): string
    {
        $p = self::$parray;
        $sbox0 = self::$sbox0;
        $sbox1 = self::$sbox1;
        $sbox2 = self::$sbox2;
        $sbox3 = self::$sbox3;

        $cdata = array_values(unpack('N*', 'OxychromaticBlowfishSwatDynamite'));
        $sha2pass = array_values(unpack('N*', $sha2pass));
        $sha2salt = array_values(unpack('N*', $sha2salt));

        self::expandstate($sha2salt, $sha2pass, $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 0; $i < 64; $i++) {
            self::expand0state($sha2salt, $sbox0, $sbox1, $sbox2, $sbox3, $p);
            self::expand0state($sha2pass, $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        for ($i = 0; $i < 64; $i++) {
            for ($j = 0; $j < 8; $j += 2) { // count($cdata) == 8
                [$cdata[$j], $cdata[$j + 1]] = self::encryptBlockHelperFast($cdata[$j], $cdata[$j + 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
            }
        }

        return pack('L*', ...$cdata);
    }

    /**
     * Performs OpenSSH-style bcrypt
     */
    public static function bcrypt_pbkdf(string $pass, string $salt, int $keylen, int $rounds): string
    {
        self::initialize_static_variables();

        if (PHP_INT_SIZE == 4) {
            throw new \RuntimeException('bcrypt is far too slow to be practical on 32-bit versions of PHP');
        }

        $sha2pass = hash('sha512', $pass, true);
        $results = [];
        $count = 1;
        while (32 * count($results) < $keylen) {
            $countsalt = $salt . pack('N', $count++);
            $sha2salt = hash('sha512', $countsalt, true);
            $out = $tmpout = self::bcrypt_hash($sha2pass, $sha2salt);
            for ($i = 1; $i < $rounds; $i++) {
                $sha2salt = hash('sha512', $tmpout, true);
                $tmpout = self::bcrypt_hash($sha2pass, $sha2salt);
                $out ^= $tmpout;
            }
            $results[] = $out;
        }
        $output = '';
        for ($i = 0; $i < 32; $i++) {
            foreach ($results as $result) {
                $output .= $result[$i];
            }
        }
        return substr($output, 0, $keylen);
    }

    /**
     * Key expansion without salt
     *
     * @access private
     * @param int[] $key
     * @param int[] $sbox0
     * @param int[] $sbox1
     * @param int[] $sbox2
     * @param int[] $sbox3
     * @param int[] $p
     * @see self::_bcrypt_hash()
     */
    private static function expand0state(array $key, array &$sbox0, array &$sbox1, array &$sbox2, array &$sbox3, array &$p): void
    {
        // expand0state is basically the same thing as this:
        //return self::expandstate(array_fill(0, 16, 0), $key);
        // but this separate function eliminates a bunch of XORs and array lookups

        $p = [
            $p[0] ^ $key[0],
            $p[1] ^ $key[1],
            $p[2] ^ $key[2],
            $p[3] ^ $key[3],
            $p[4] ^ $key[4],
            $p[5] ^ $key[5],
            $p[6] ^ $key[6],
            $p[7] ^ $key[7],
            $p[8] ^ $key[8],
            $p[9] ^ $key[9],
            $p[10] ^ $key[10],
            $p[11] ^ $key[11],
            $p[12] ^ $key[12],
            $p[13] ^ $key[13],
            $p[14] ^ $key[14],
            $p[15] ^ $key[15],
            $p[16] ^ $key[0],
            $p[17] ^ $key[1],
        ];

        [$p[0], $p[1]] = self::encryptBlockHelperFast(0, 0, $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2; $i < 18; $i += 2) {
            [$p[$i], $p[$i + 1]] = self::encryptBlockHelperFast($p[$i - 2], $p[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox0[0], $sbox0[1]] = self::encryptBlockHelperFast($p[16], $p[17], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2; $i < 256; $i += 2) {
            [$sbox0[$i], $sbox0[$i + 1]] = self::encryptBlockHelperFast($sbox0[$i - 2], $sbox0[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox1[0], $sbox1[1]] = self::encryptBlockHelperFast($sbox0[254], $sbox0[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2; $i < 256; $i += 2) {
            [$sbox1[$i], $sbox1[$i + 1]] = self::encryptBlockHelperFast($sbox1[$i - 2], $sbox1[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox2[0], $sbox2[1]] = self::encryptBlockHelperFast($sbox1[254], $sbox1[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2; $i < 256; $i += 2) {
            [$sbox2[$i], $sbox2[$i + 1]] = self::encryptBlockHelperFast($sbox2[$i - 2], $sbox2[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox3[0], $sbox3[1]] = self::encryptBlockHelperFast($sbox2[254], $sbox2[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2; $i < 256; $i += 2) {
            [$sbox3[$i], $sbox3[$i + 1]] = self::encryptBlockHelperFast($sbox3[$i - 2], $sbox3[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }
    }

    /**
     * Key expansion with salt
     *
     * @access private
     * @param int[] $data
     * @param int[] $key
     * @param int[] $sbox0
     * @param int[] $sbox1
     * @param int[] $sbox2
     * @param int[] $sbox3
     * @param int[] $p
     * @see self::_bcrypt_hash()
     */
    private static function expandstate(array $data, array $key, array &$sbox0, array &$sbox1, array &$sbox2, array &$sbox3, array &$p): void
    {
        $p = [
            $p[0] ^ $key[0],
            $p[1] ^ $key[1],
            $p[2] ^ $key[2],
            $p[3] ^ $key[3],
            $p[4] ^ $key[4],
            $p[5] ^ $key[5],
            $p[6] ^ $key[6],
            $p[7] ^ $key[7],
            $p[8] ^ $key[8],
            $p[9] ^ $key[9],
            $p[10] ^ $key[10],
            $p[11] ^ $key[11],
            $p[12] ^ $key[12],
            $p[13] ^ $key[13],
            $p[14] ^ $key[14],
            $p[15] ^ $key[15],
            $p[16] ^ $key[0],
            $p[17] ^ $key[1],
        ];

        [$p[0], $p[1]] = self::encryptBlockHelperFast($data[0], $data[1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2, $j = 2; $i < 18; $i += 2, $j = ($j + 2) % 16) {
            [$p[$i], $p[$i + 1]] = self::encryptBlockHelperFast($data[$j] ^ $p[$i - 2], $data[$j + 1] ^ $p[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox0[0], $sbox0[1]] = self::encryptBlockHelperFast($data[2] ^ $p[16], $data[3] ^ $p[17], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2, $j = 4; $i < 256; $i += 2, $j = ($j + 2) % 16) { // instead of 16 maybe count($data) would be better?
            [$sbox0[$i], $sbox0[$i + 1]] = self::encryptBlockHelperFast($data[$j] ^ $sbox0[$i - 2], $data[$j + 1] ^ $sbox0[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox1[0], $sbox1[1]] = self::encryptBlockHelperFast($data[2] ^ $sbox0[254], $data[3] ^ $sbox0[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2, $j = 4; $i < 256; $i += 2, $j = ($j + 2) % 16) {
            [$sbox1[$i], $sbox1[$i + 1]] = self::encryptBlockHelperFast($data[$j] ^ $sbox1[$i - 2], $data[$j + 1] ^ $sbox1[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox2[0], $sbox2[1]] = self::encryptBlockHelperFast($data[2] ^ $sbox1[254], $data[3] ^ $sbox1[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2, $j = 4; $i < 256; $i += 2, $j = ($j + 2) % 16) {
            [$sbox2[$i], $sbox2[$i + 1]] = self::encryptBlockHelperFast($data[$j] ^ $sbox2[$i - 2], $data[$j + 1] ^ $sbox2[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }

        [$sbox3[0], $sbox3[1]] = self::encryptBlockHelperFast($data[2] ^ $sbox2[254], $data[3] ^ $sbox2[255], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        for ($i = 2, $j = 4; $i < 256; $i += 2, $j = ($j + 2) % 16) {
            [$sbox3[$i], $sbox3[$i + 1]] = self::encryptBlockHelperFast($data[$j] ^ $sbox3[$i - 2], $data[$j + 1] ^ $sbox3[$i - 1], $sbox0, $sbox1, $sbox2, $sbox3, $p);
        }
    }

    /**
     * Encrypts a block
     */
    protected function encryptBlock(string $in): string
    {
        $p = $this->bctx['p'];
        // extract($this->bctx['sb'], EXTR_PREFIX_ALL, 'sb'); // slower
        $sb_0 = $this->bctx['sb'][0];
        $sb_1 = $this->bctx['sb'][1];
        $sb_2 = $this->bctx['sb'][2];
        $sb_3 = $this->bctx['sb'][3];

        $in = unpack('N*', $in);
        $l = $in[1];
        $r = $in[2];

        [$r, $l] = PHP_INT_SIZE == 4 ?
            self::encryptBlockHelperSlow($l, $r, $sb_0, $sb_1, $sb_2, $sb_3, $p) :
            self::encryptBlockHelperFast($l, $r, $sb_0, $sb_1, $sb_2, $sb_3, $p);

        return pack("N*", $r, $l);
    }

    /**
     * Fast helper function for block encryption
     *
     * @access private
     * @param int[] $sbox0
     * @param int[] $sbox1
     * @param int[] $sbox2
     * @param int[] $sbox3
     * @param int[] $p
     * @return int[]
     */
    private static function encryptBlockHelperFast(int $x0, int $x1, array $sbox0, array $sbox1, array $sbox2, array $sbox3, array $p): array
    {
        $x0 ^= $p[0];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[1];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[2];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[3];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[4];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[5];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[6];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[7];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[8];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[9];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[10];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[11];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[12];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[13];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[14];
        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[15];
        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[16];

        return [$x1 & 0xFFFFFFFF ^ $p[17], $x0 & 0xFFFFFFFF];
    }

    /**
     * Slow helper function for block encryption
     *
     * @access private
     * @param int[] $sbox0
     * @param int[] $sbox1
     * @param int[] $sbox2
     * @param int[] $sbox3
     * @param int[] $p
     * @return int[]
     */
    private static function encryptBlockHelperSlow(int $x0, int $x1, array $sbox0, array $sbox1, array $sbox2, array $sbox3, array $p): array
    {
        // -16777216 == intval(0xFF000000) on 32-bit PHP installs
        $x0 ^= $p[0];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[1];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[2];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[3];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[4];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[5];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[6];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[7];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[8];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[9];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[10];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[11];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[12];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[13];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[14];
        $x1 ^= intval((intval($sbox0[(($x0 & -16777216) >> 24) & 0xFF] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[15];
        $x0 ^= intval((intval($sbox0[(($x1 & -16777216) >> 24) & 0xFF] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[16];

        return [$x1 ^ $p[17], $x0];
    }

    /**
     * Decrypts a block
     */
    protected function decryptBlock(string $in): string
    {
        $p = $this->bctx['p'];
        $sb_0 = $this->bctx['sb'][0];
        $sb_1 = $this->bctx['sb'][1];
        $sb_2 = $this->bctx['sb'][2];
        $sb_3 = $this->bctx['sb'][3];

        $in = unpack('N*', $in);
        $l = $in[1];
        $r = $in[2];

        for ($i = 17; $i > 2; $i -= 2) {
            $l ^= $p[$i];
            $r ^= intval((intval($sb_0[$l >> 24 & 0xff] + $sb_1[$l >> 16 & 0xff]) ^
                  $sb_2[$l >>  8 & 0xff]) +
                  $sb_3[$l       & 0xff]);

            $r ^= $p[$i - 1];
            $l ^= intval((intval($sb_0[$r >> 24 & 0xff] + $sb_1[$r >> 16 & 0xff]) ^
                  $sb_2[$r >>  8 & 0xff]) +
                  $sb_3[$r       & 0xff]);
        }
        return pack('N*', $r ^ $p[0], $l ^ $p[1]);
    }

    /**
     * Setup the performance-optimized function for de/encrypt()
     *
     * @see \phpseclib3\Crypt\Common\SymmetricKey::_setupInlineCrypt()
     */
    protected function setupInlineCrypt(): void
    {
        $p = $this->bctx['p'];
        $init_crypt = '
            static $sb_0, $sb_1, $sb_2, $sb_3;
            if (!$sb_0) {
                $sb_0 = $this->bctx["sb"][0];
                $sb_1 = $this->bctx["sb"][1];
                $sb_2 = $this->bctx["sb"][2];
                $sb_3 = $this->bctx["sb"][3];
            }
        ';

        // Generating encrypt code:
        $encrypt_block = '
            $in = unpack("N*", $in);
            $l = $in[1];
            $r = $in[2];
        ';
        for ($i = 0; $i < 16; $i += 2) {
            $encrypt_block .= '
                $l^= ' . $p[$i] . ';
                $r^= intval((intval($sb_0[$l >> 24 & 0xff] + $sb_1[$l >> 16 & 0xff]) ^
                      $sb_2[$l >>  8 & 0xff]) +
                      $sb_3[$l       & 0xff]);

                $r^= ' . $p[$i + 1] . ';
                $l^= intval((intval($sb_0[$r >> 24 & 0xff] + $sb_1[$r >> 16 & 0xff])  ^
                      $sb_2[$r >>  8 & 0xff]) +
                      $sb_3[$r       & 0xff]);
            ';
        }
        $encrypt_block .= '
            $in = pack("N*",
                $r ^ ' . $p[17] . ',
                $l ^ ' . $p[16] . '
            );
        ';

         // Generating decrypt code:
        $decrypt_block = '
            $in = unpack("N*", $in);
            $l = $in[1];
            $r = $in[2];
        ';

        for ($i = 17; $i > 2; $i -= 2) {
            $decrypt_block .= '
                $l^= ' . $p[$i] . ';
                $r^= intval((intval($sb_0[$l >> 24 & 0xff] + $sb_1[$l >> 16 & 0xff]) ^
                      $sb_2[$l >>  8 & 0xff]) +
                      $sb_3[$l       & 0xff]);

                $r^= ' . $p[$i - 1] . ';
                $l^= intval((intval($sb_0[$r >> 24 & 0xff] + $sb_1[$r >> 16 & 0xff]) ^
                      $sb_2[$r >>  8 & 0xff]) +
                      $sb_3[$r       & 0xff]);
            ';
        }

        $decrypt_block .= '
            $in = pack("N*",
                $r ^ ' . $p[0] . ',
                $l ^ ' . $p[1] . '
            );
        ';

        $this->inline_crypt = $this->createInlineCryptFunction(
            [
               'init_crypt'    => $init_crypt,
               'init_encrypt'  => '',
               'init_decrypt'  => '',
               'encrypt_block' => $encrypt_block,
               'decrypt_block' => $decrypt_block,
            ]
        );
    }
}