// Copyright (c) 2006 Damien Miller <djm@mindrot.org>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

package com.jcraft.jsch.jbcrypt;

import java.nio.charset.StandardCharsets;
import java.security.DigestException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * BCrypt implements OpenBSD-style Blowfish password hashing using the scheme described in "A
 * Future-Adaptable Password Scheme" by Niels Provos and David Mazieres.
 *
 * <p>
 * This password hashing system tries to thwart off-line password cracking using a
 * computationally-intensive hashing algorithm, based on Bruce Schneier's Blowfish cipher. The work
 * factor of the algorithm is parameterised, so it can be increased as computers get faster.
 *
 * <p>
 * Usage is really simple. To hash a password for the first time, call the hashpw method with a
 * random salt, like this:
 *
 * <p>
 * <code>
 * String pw_hash = BCrypt.hashpw(plain_password, BCrypt.gensalt()); <br>
 * </code>
 *
 * <p>
 * To check whether a plaintext password matches one that has been hashed previously, use the
 * checkpw method:
 *
 * <p>
 * <code>
 * if (BCrypt.checkpw(candidate_password, stored_hash))<br>
 * &nbsp;&nbsp;&nbsp;&nbsp;System.out.println("It matches");<br>
 * else<br>
 * &nbsp;&nbsp;&nbsp;&nbsp;System.out.println("It does not match");<br>
 * </code>
 *
 * <p>
 * The gensalt() method takes an optional parameter (log_rounds) that determines the computational
 * complexity of the hashing:
 *
 * <p>
 * <code>
 * String strong_salt = BCrypt.gensalt(10)<br>
 * String stronger_salt = BCrypt.gensalt(12)<br>
 * </code>
 *
 * <p>
 * The amount of work increases exponentially (2**log_rounds), so each increment is twice as much
 * work. The default log_rounds is 10, and the valid range is 4 to 30.
 *
 * @author Damien Miller
 * @version 0.2
 */
public class BCrypt {
  // BCrypt parameters
  private static final int GENSALT_DEFAULT_LOG2_ROUNDS = 10;
  private static final int BCRYPT_SALT_LEN = 16;

  // Blowfish parameters
  private static final int BLOWFISH_NUM_ROUNDS = 16;

  // Initial contents of key schedule
  private static final int P_orig[] = {0x243f6a88, 0x85a308d3, 0x13198a2e, 0x03707344, 0xa4093822,
      0x299f31d0, 0x082efa98, 0xec4e6c89, 0x452821e6, 0x38d01377, 0xbe5466cf, 0x34e90c6c,
      0xc0ac29b7, 0xc97c50dd, 0x3f84d5b5, 0xb5470917, 0x9216d5d9, 0x8979fb1b};
  private static final int S_orig[] = {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, 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, 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,
      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};

  // OpenBSD IV: "OxychromaticBlowfishSwatDynamite" in big endian
  private static final int[] openbsd_iv = new int[] {0x4f787963, 0x68726f6d, 0x61746963, 0x426c6f77,
      0x66697368, 0x53776174, 0x44796e61, 0x6d697465};

  // bcrypt IV: "OrpheanBeholderScryDoubt". The C implementation calls
  // this "ciphertext", but it is really plaintext or an IV. We keep
  // the name to make code comparison easier.
  private static final int bf_crypt_ciphertext[] =
      {0x4f727068, 0x65616e42, 0x65686f6c, 0x64657253, 0x63727944, 0x6f756274};

  // Table for Base64 encoding
  private static final char base64_code[] = {'.', '/', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
      'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b',
      'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u',
      'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};

  // Table for Base64 decoding
  private static final byte index_64[] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, -1, -1, -1,
      -1, -1, -1, -1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
      23, 24, 25, 26, 27, -1, -1, -1, -1, -1, -1, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
      40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, -1, -1, -1, -1, -1};

  // Expanded Blowfish key
  private int P[];
  private int S[];

  /**
   * Encode a byte array using bcrypt's slightly-modified base64 encoding scheme. Note that this is
   * *not* compatible with the standard MIME-base64 encoding.
   *
   * @param d the byte array to encode
   * @param len the number of bytes to encode
   * @return base64-encoded string
   * @exception IllegalArgumentException if the length is invalid
   */
  private static String encode_base64(byte d[], int len) throws IllegalArgumentException {
    int off = 0;
    StringBuilder rs = new StringBuilder();
    int c1, c2;

    if (len <= 0 || len > d.length)
      throw new IllegalArgumentException("Invalid len");

    while (off < len) {
      c1 = d[off++] & 0xff;
      rs.append(base64_code[(c1 >> 2) & 0x3f]);
      c1 = (c1 & 0x03) << 4;
      if (off >= len) {
        rs.append(base64_code[c1 & 0x3f]);
        break;
      }
      c2 = d[off++] & 0xff;
      c1 |= (c2 >> 4) & 0x0f;
      rs.append(base64_code[c1 & 0x3f]);
      c1 = (c2 & 0x0f) << 2;
      if (off >= len) {
        rs.append(base64_code[c1 & 0x3f]);
        break;
      }
      c2 = d[off++] & 0xff;
      c1 |= (c2 >> 6) & 0x03;
      rs.append(base64_code[c1 & 0x3f]);
      rs.append(base64_code[c2 & 0x3f]);
    }
    return rs.toString();
  }

  /**
   * Look up the 3 bits base64-encoded by the specified character, range-checking againt conversion
   * table
   *
   * @param x the base64-encoded value
   * @return the decoded value of x
   */
  private static byte char64(char x) {
    if ((int) x < 0 || (int) x > index_64.length)
      return -1;
    return index_64[(int) x];
  }

  /**
   * Decode a string encoded using bcrypt's base64 scheme to a byte array. Note that this is *not*
   * compatible with the standard MIME-base64 encoding.
   *
   * @param s the string to decode
   * @param maxolen the maximum number of bytes to decode
   * @return an array containing the decoded bytes
   * @throws IllegalArgumentException if maxolen is invalid
   */
  private static byte[] decode_base64(String s, int maxolen) throws IllegalArgumentException {
    StringBuilder rs = new StringBuilder();
    int off = 0, slen = s.length(), olen = 0;
    byte ret[];
    byte c1, c2, c3, c4, o;

    if (maxolen <= 0)
      throw new IllegalArgumentException("Invalid maxolen");

    while (off < slen - 1 && olen < maxolen) {
      c1 = char64(s.charAt(off++));
      c2 = char64(s.charAt(off++));
      if (c1 == -1 || c2 == -1)
        break;
      o = (byte) (c1 << 2);
      o |= (byte) ((c2 & 0x30) >> 4);
      rs.append((char) o);
      if (++olen >= maxolen || off >= slen)
        break;
      c3 = char64(s.charAt(off++));
      if (c3 == -1)
        break;
      o = (byte) ((c2 & 0x0f) << 4);
      o |= (byte) ((c3 & 0x3c) >> 2);
      rs.append((char) o);
      if (++olen >= maxolen || off >= slen)
        break;
      c4 = char64(s.charAt(off++));
      o = (byte) ((c3 & 0x03) << 6);
      o |= c4;
      rs.append((char) o);
      ++olen;
    }

    ret = new byte[olen];
    for (off = 0; off < olen; off++)
      ret[off] = (byte) rs.charAt(off);
    return ret;
  }

  /**
   * Blowfish encipher a single 64-bit block encoded as two 32-bit halves
   *
   * @param lr an array containing the two 32-bit half blocks
   * @param off the position in the array of the blocks
   */
  private final void encipher(int lr[], int off) {
    int i, n, l = lr[off], r = lr[off + 1];

    l ^= P[0];
    for (i = 0; i <= BLOWFISH_NUM_ROUNDS - 2;) {
      // Feistel substitution on left word
      n = S[(l >> 24) & 0xff];
      n += S[0x100 | ((l >> 16) & 0xff)];
      n ^= S[0x200 | ((l >> 8) & 0xff)];
      n += S[0x300 | (l & 0xff)];
      r ^= n ^ P[++i];

      // Feistel substitution on right word
      n = S[(r >> 24) & 0xff];
      n += S[0x100 | ((r >> 16) & 0xff)];
      n ^= S[0x200 | ((r >> 8) & 0xff)];
      n += S[0x300 | (r & 0xff)];
      l ^= n ^ P[++i];
    }
    lr[off] = r ^ P[BLOWFISH_NUM_ROUNDS + 1];
    lr[off + 1] = l;
  }

  /**
   * Cycically extract a word of key material
   *
   * @param data the string to extract the data from
   * @param offp a "pointer" (as a one-entry array) to the current offset into data
   * @return the next word of material from data
   */
  private static int streamtoword(byte data[], int offp[]) {
    int i;
    int word = 0;
    int off = offp[0];

    for (i = 0; i < 4; i++) {
      word = (word << 8) | (data[off] & 0xff);
      off = (off + 1) % data.length;
    }

    offp[0] = off;
    return word;
  }

  /** Initialise the Blowfish key schedule */
  private void init_key() {
    P = P_orig.clone();
    S = S_orig.clone();
  }

  /**
   * Key the Blowfish cipher
   *
   * @param key an array containing the key
   */
  private void key(byte key[]) {
    int i;
    int koffp[] = {0};
    int lr[] = {0, 0};
    int plen = P.length, slen = S.length;

    for (i = 0; i < plen; i++)
      P[i] = P[i] ^ streamtoword(key, koffp);

    for (i = 0; i < plen; i += 2) {
      encipher(lr, 0);
      P[i] = lr[0];
      P[i + 1] = lr[1];
    }

    for (i = 0; i < slen; i += 2) {
      encipher(lr, 0);
      S[i] = lr[0];
      S[i + 1] = lr[1];
    }
  }

  /**
   * Perform the "enhanced key schedule" step described by Provos and Mazieres in "A
   * Future-Adaptable Password Scheme" http://www.openbsd.org/papers/bcrypt-paper.ps
   *
   * @param data salt information
   * @param key password information
   */
  private void ekskey(byte data[], byte key[]) {
    int i;
    int koffp[] = {0}, doffp[] = {0};
    int lr[] = {0, 0};
    int plen = P.length, slen = S.length;

    for (i = 0; i < plen; i++)
      P[i] = P[i] ^ streamtoword(key, koffp);

    for (i = 0; i < plen; i += 2) {
      lr[0] ^= streamtoword(data, doffp);
      lr[1] ^= streamtoword(data, doffp);
      encipher(lr, 0);
      P[i] = lr[0];
      P[i + 1] = lr[1];
    }

    for (i = 0; i < slen; i += 2) {
      lr[0] ^= streamtoword(data, doffp);
      lr[1] ^= streamtoword(data, doffp);
      encipher(lr, 0);
      S[i] = lr[0];
      S[i + 1] = lr[1];
    }
  }

  /** Compatibility with new OpenBSD function. */
  public void hash(byte[] hpass, byte[] hsalt, byte[] output) {
    init_key();
    ekskey(hsalt, hpass);
    for (int i = 0; i < 64; i++) {
      key(hsalt);
      key(hpass);
    }

    int[] buf = new int[openbsd_iv.length];
    System.arraycopy(openbsd_iv, 0, buf, 0, openbsd_iv.length);
    for (int i = 0; i < 8; i += 2) {
      for (int j = 0; j < 64; j++) {
        encipher(buf, i);
      }
    }

    for (int i = 0, j = 0; i < buf.length; i++) {
      // Output of this is little endian
      output[j++] = (byte) (buf[i] & 0xff);
      output[j++] = (byte) ((buf[i] >> 8) & 0xff);
      output[j++] = (byte) ((buf[i] >> 16) & 0xff);
      output[j++] = (byte) ((buf[i] >> 24) & 0xff);
    }
  }

  /** Compatibility with new OpenBSD function. */
  public void pbkdf(byte[] password, byte[] salt, int rounds, byte[] output) {
    try {
      MessageDigest sha512 = MessageDigest.getInstance("SHA-512");

      int nblocks = (output.length + 31) / 32;
      byte[] hpass = sha512.digest(password);

      byte[] hsalt = new byte[64];
      byte[] block_b = new byte[4];
      byte[] out = new byte[32];
      byte[] tmp = new byte[32];
      for (int block = 1; block <= nblocks; block++) {
        // Block count is in big endian
        block_b[0] = (byte) ((block >> 24) & 0xFF);
        block_b[1] = (byte) ((block >> 16) & 0xFF);
        block_b[2] = (byte) ((block >> 8) & 0xFF);
        block_b[3] = (byte) (block & 0xFF);

        sha512.reset();
        sha512.update(salt);
        sha512.update(block_b);
        sha512.digest(hsalt, 0, hsalt.length);

        hash(hpass, hsalt, out);
        System.arraycopy(out, 0, tmp, 0, out.length);

        for (int round = 1; round < rounds; round++) {
          sha512.reset();
          sha512.update(tmp);
          sha512.digest(hsalt, 0, hsalt.length);

          hash(hpass, hsalt, tmp);

          for (int i = 0; i < tmp.length; i++) {
            out[i] ^= tmp[i];
          }
        }

        for (int i = 0; i < out.length; i++) {
          int idx = i * nblocks + (block - 1);
          if (idx < output.length) {
            output[idx] = out[i];
          }
        }
      }
    } catch (DigestException e) {
      throw new RuntimeException(e);
    } catch (NoSuchAlgorithmException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Perform the central password hashing step in the bcrypt scheme
   *
   * @param password the password to hash
   * @param salt the binary salt to hash with the password
   * @param log_rounds the binary logarithm of the number of rounds of hashing to apply
   * @param cdata the plaintext to encrypt
   * @return an array containing the binary hashed password
   */
  public byte[] crypt_raw(byte password[], byte salt[], int log_rounds, int cdata[]) {
    int rounds, i, j;
    int clen = cdata.length;
    byte ret[];

    if (log_rounds < 4 || log_rounds > 30)
      throw new IllegalArgumentException("Bad number of rounds");
    rounds = 1 << log_rounds;
    if (salt.length != BCRYPT_SALT_LEN)
      throw new IllegalArgumentException("Bad salt length");

    init_key();
    ekskey(salt, password);
    for (i = 0; i != rounds; i++) {
      key(password);
      key(salt);
    }

    for (i = 0; i < 64; i++) {
      for (j = 0; j < (clen >> 1); j++)
        encipher(cdata, j << 1);
    }

    ret = new byte[clen * 4];
    for (i = 0, j = 0; i < clen; i++) {
      ret[j++] = (byte) ((cdata[i] >> 24) & 0xff);
      ret[j++] = (byte) ((cdata[i] >> 16) & 0xff);
      ret[j++] = (byte) ((cdata[i] >> 8) & 0xff);
      ret[j++] = (byte) (cdata[i] & 0xff);
    }
    return ret;
  }

  /**
   * Hash a password using the OpenBSD bcrypt scheme
   *
   * @param password the password to hash
   * @param salt the salt to hash with (perhaps generated using BCrypt.gensalt)
   * @return the hashed password
   */
  public static String hashpw(String password, String salt) {
    BCrypt B;
    String real_salt;
    byte passwordb[], saltb[], hashed[];
    char minor = (char) 0;
    int rounds, off = 0;
    StringBuilder rs = new StringBuilder();

    if (salt.charAt(0) != '$' || salt.charAt(1) != '2')
      throw new IllegalArgumentException("Invalid salt version");
    if (salt.charAt(2) == '$')
      off = 3;
    else {
      minor = salt.charAt(2);
      if (minor != 'a' || salt.charAt(3) != '$')
        throw new IllegalArgumentException("Invalid salt revision");
      off = 4;
    }

    // Extract number of rounds
    if (salt.charAt(off + 2) > '$')
      throw new IllegalArgumentException("Missing salt rounds");
    rounds = Integer.parseInt(salt.substring(off, off + 2));

    real_salt = salt.substring(off + 3, off + 25);
    passwordb = (password + (minor >= 'a' ? "\000" : "")).getBytes(StandardCharsets.UTF_8);

    saltb = decode_base64(real_salt, BCRYPT_SALT_LEN);

    B = new BCrypt();
    hashed = B.crypt_raw(passwordb, saltb, rounds, bf_crypt_ciphertext.clone());

    rs.append("$2");
    if (minor >= 'a')
      rs.append(minor);
    rs.append("$");
    if (rounds < 10)
      rs.append("0");
    if (rounds > 30) {
      throw new IllegalArgumentException("rounds exceeds maximum (30)");
    }
    rs.append(Integer.toString(rounds));
    rs.append("$");
    rs.append(encode_base64(saltb, saltb.length));
    rs.append(encode_base64(hashed, bf_crypt_ciphertext.length * 4 - 1));
    return rs.toString();
  }

  /**
   * Generate a salt for use with the BCrypt.hashpw() method
   *
   * @param log_rounds the log2 of the number of rounds of hashing to apply - the work factor
   *        therefore increases as 2**log_rounds.
   * @param random an instance of SecureRandom to use
   * @return an encoded salt value
   */
  public static String gensalt(int log_rounds, SecureRandom random) {
    StringBuilder rs = new StringBuilder();
    byte rnd[] = new byte[BCRYPT_SALT_LEN];

    random.nextBytes(rnd);

    rs.append("$2a$");
    if (log_rounds < 10)
      rs.append("0");
    if (log_rounds > 30) {
      throw new IllegalArgumentException("log_rounds exceeds maximum (30)");
    }
    rs.append(Integer.toString(log_rounds));
    rs.append("$");
    rs.append(encode_base64(rnd, rnd.length));
    return rs.toString();
  }

  /**
   * Generate a salt for use with the BCrypt.hashpw() method
   *
   * @param log_rounds the log2 of the number of rounds of hashing to apply - the work factor
   *        therefore increases as 2**log_rounds.
   * @return an encoded salt value
   */
  public static String gensalt(int log_rounds) {
    return gensalt(log_rounds, new SecureRandom());
  }

  /**
   * Generate a salt for use with the BCrypt.hashpw() method, selecting a reasonable default for the
   * number of hashing rounds to apply
   *
   * @return an encoded salt value
   */
  public static String gensalt() {
    return gensalt(GENSALT_DEFAULT_LOG2_ROUNDS);
  }

  /**
   * Check that a plaintext password matches a previously hashed one
   *
   * @param plaintext the plaintext password to verify
   * @param hashed the previously-hashed password
   * @return true if the passwords match, false otherwise
   */
  public static boolean checkpw(String plaintext, String hashed) {
    String try_pw = hashpw(plaintext, hashed);
    byte hashed_bytes[] = hashed.getBytes(StandardCharsets.UTF_8);
    byte try_bytes[] = try_pw.getBytes(StandardCharsets.UTF_8);
    if (hashed_bytes.length != try_bytes.length)
      return false;
    byte ret = 0;
    for (int i = 0; i < try_bytes.length; i++)
      ret |= (byte) (hashed_bytes[i] ^ try_bytes[i]);
    return ret == 0;
  }
}
