package org.bouncycastle.crypto.generators;

import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.digests.SHA512Digest;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.Pack;
import org.bouncycastle.util.Strings;

/**
 * Core of password hashing scheme Bcrypt,
 * designed by Niels Provos and David Mazières,
 * corresponds to the C reference implementation.
 * <p>
 * This implementation does not correspondent to the 1999 published paper
 * "A Future-Adaptable Password Scheme" of Niels Provos and David Mazières,
 * see: https://www.usenix.org/legacy/events/usenix99/provos/provos_html/node1.html.
 * In contrast to the paper, the order of key setup and salt setup is reversed:
 * state &lt;- ExpandKey(state, 0, key)
 * state &lt;- ExpandKey(state, 0, salt)
 * This corresponds to the OpenBSD reference implementation of Bcrypt. 
 * </p><p>
 * Note: 
 * There is no successful cryptanalysis (status 2015), but
 * the amount of memory and the band width of Bcrypt
 * may be insufficient to effectively prevent attacks 
 * with custom hardware like FPGAs, ASICs
 * </p><p>
 * This implementation uses some parts of Bouncy Castle's BlowfishEngine.
 * </p>
 */
public final class BCrypt
{
    // magic String "OrpheanBeholderScryDoubt" is used as clear text for encryption
    private static final int[] MAGIC_STRING =
        {
            0x4F727068, 0x65616E42, 0x65686F6C,
            0x64657253, 0x63727944, 0x6F756274
        };
    final static int MAGIC_STRING_LENGTH = 6;


    private final static int[]
        KP = {
        0x243F6A88, 0x85A308D3, 0x13198A2E, 0x03707344,
        0xA4093822, 0x299F31D0, 0x082EFA98, 0xEC4E6C89,
        0x452821E6, 0x38D01377, 0xBE5466CF, 0x34E90C6C,
        0xC0AC29B7, 0xC97C50DD, 0x3F84D5B5, 0xB5470917,
        0x9216D5D9, 0x8979FB1B
    },

    KS0 = {
        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
    },

    KS1 = {
        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
    },

    KS2 = {
        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
    },

    KS3 = {
        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
    };

    //====================================
    // Useful constants
    //====================================

    private static final int ROUNDS = 16;
    private static final int SBOX_SK = 256;
    private static final int SBOX_SK2 = SBOX_SK * 2;
    private static final int SBOX_SK3 = SBOX_SK * 3;
    private static final int P_SZ = ROUNDS + 2;


    private final int[] S;    // the s-boxes
    private final int[] P;    // the p-array

    private BCrypt()
    {
        S = new int[SBOX_SK * 4];
        P = new int[P_SZ];
    }

    //==================================
    // Private Implementation
    //==================================

    private int F(int x)
    {
        return (((S[(x >>> 24)] + S[SBOX_SK + ((x >>> 16) & 0xff)])
            ^ S[SBOX_SK2 + ((x >>> 8) & 0xff)]) + S[SBOX_SK3 + (x & 0xff)]);
    }

    /*
     * apply the encryption cycle to each value pair in the table.
     */
    private void processTable(
        int xl,
        int xr,
        int[] table)
    {
        int size = table.length;

        for (int s = 0; s < size; s += 2)
        {
            xl ^= P[0];

            for (int i = 1; i < ROUNDS; i += 2)
            {
                xr ^= F(xl) ^ P[i];
                xl ^= F(xr) ^ P[i + 1];
            }

            xr ^= P[ROUNDS + 1];

            table[s] = xr;
            table[s + 1] = xl;  // lgtm [java/index-out-of-bounds]

            xr = xl;            // end of cycle swap
            xl = table[s];
        }
    }

    /*
     * Initialize the S-boxes and the P-array, with a fixed string
     * This string contains the hexadecimal digits of pi (3.141...)
     */
    private void initState()
    {
        System.arraycopy(KS0, 0, S, 0, SBOX_SK);
        System.arraycopy(KS1, 0, S, SBOX_SK, SBOX_SK);
        System.arraycopy(KS2, 0, S, SBOX_SK2, SBOX_SK);
        System.arraycopy(KS3, 0, S, SBOX_SK3, SBOX_SK);

        System.arraycopy(KP, 0, P, 0, P_SZ);

    }

    /*
     * XOR P with key cyclic.
     * This is the first part of ExpandKey function
     */
    private final void cyclicXorKey(byte[] key)
    {
        int keyLength = key.length;
        int keyIndex = 0;

        for (int i = 0; i < P_SZ; i++)
        {
            // get the 32 bits of the key, in 4 * 8 bit chunks
            int data = 0x0000000;
            for (int j = 0; j < 4; j++)
            {
                // create a 32 bit block
                data = (data << 8) | (key[keyIndex++] & 0xff);

                // wrap when we get to the end of the key
                if (keyIndex >= keyLength)
                {
                    keyIndex = 0;
                }
            }
            // XOR the newly created 32 bit chunk onto the P-array
            P[i] ^= data;
        }
    }


    /*
     *  encrypt magic String 64 times in ECB
     */
    private byte[] encryptMagicString()
    {
        int[] text = {
            MAGIC_STRING[0], MAGIC_STRING[1],
            MAGIC_STRING[2], MAGIC_STRING[3],
            MAGIC_STRING[4], MAGIC_STRING[5]
        };
        for (int i = 0; i < 64; i++)
        {
            for (int j = 0; j < MAGIC_STRING_LENGTH; j += 2)
            {
                int left = text[j];
                int right = text[j + 1];

                left ^= P[0];
                for (int k = 1; k < ROUNDS; k += 2)
                {
                    right ^= F(left) ^ P[k];
                    left ^= F(right) ^ P[k + 1];
                }
                right ^= P[ROUNDS + 1];
                // swap values:
                text[j] = right;
                text[j + 1] = left;
            }
        }
        byte[] result = new byte[24]; // holds 192 bit key
        Pack.intToBigEndian(text, result, 0);
        Arrays.fill(text, 0);
        Arrays.fill(P, 0);
        Arrays.fill(S, 0);

        return result;
    }

    /*
     * This is a part of Eksblowfish function
     *
     * @param     table: sub-keys or working key
     * @param     salt32Bit: a 16 byte salt as two 32 bit words
     * @param     iv1: value from last proceeded table
     * @param     iv2: value from last proceeded table
     */
    private void processTableWithSalt(
        int[] table,
        int[] salt32Bit,
        int iv1,
        int iv2)
    {
        int xl = iv1 ^ salt32Bit[0];
        int xr = iv2 ^ salt32Bit[1];

        int yl;
        int yr;
        int size = table.length;

        for (int s = 0; s < size; s += 4)
        {
            xl ^= P[0];
            for (int i = 1; i < ROUNDS; i += 2)
            {
                xr ^= F(xl) ^ P[i];
                xl ^= F(xr) ^ P[i + 1];
            }
            xr ^= P[ROUNDS + 1];

            // suppress LGTM warnings index-out-of-bounds since the loop increments s by 4
            table[s] = xr;
            table[s + 1] = xl;  // lgtm [java/index-out-of-bounds]

            yl = salt32Bit[2] ^ xr;
            yr = salt32Bit[3] ^ xl;

            if (s + 2 >= size) // P holds 18 values
            {
                break;
            }

            yl ^= P[0];
            for (int i = 1; i < ROUNDS; i += 2)
            {
                yr ^= F(yl) ^ P[i];
                yl ^= F(yr) ^ P[i + 1];
            }
            yr ^= P[ROUNDS + 1];

            table[s + 2] = yr;  // lgtm [java/index-out-of-bounds]
            table[s + 3] = yl;  // lgtm [java/index-out-of-bounds]

            xl = salt32Bit[0] ^ yr;
            xr = salt32Bit[1] ^ yl;
        }
    }

    /**
     * Derives a raw 192 bit Bcrypt key
     *
     * @param cost the cost factor, treated as an exponent of 2
     * @param salt a 16 byte salt
     * @param psw  the password
     * @return a 192 bit key
     */
    private final byte[] deriveRawKey(
        int cost,
        byte[] salt,
        byte[] psw)
    {
        if (salt.length != 16)
        {
            throw new DataLengthException("Invalid salt size: 16 bytes expected.");
        }
        if (cost < 4 || cost > 31)
        {
            throw new IllegalArgumentException("Illegal cost factor: 4 - 31 expected.");
        }

        if (psw.length == 0)
        {
            psw = new byte[4];
        }

        // state <- InitState()
        initState();

        int[] salt32Bit = new int[4]; // holds 16 byte salt
        Pack.bigEndianToInt(salt, 0, salt32Bit);

        int[] salt32Bit2 = new int[salt.length]; // swapped values
        salt32Bit2[0] = salt32Bit[2];
        salt32Bit2[1] = salt32Bit[3];
        salt32Bit2[2] = salt32Bit[0];
        salt32Bit2[3] = salt32Bit[1];

        // ExpandKey( state, salt, key):
        cyclicXorKey(psw);
        processTableWithSalt(P, salt32Bit, 0, 0);
        Arrays.fill(salt32Bit, 0);
        processTableWithSalt(S, salt32Bit2, P[P.length - 2], P[P.length - 1]);
        Arrays.fill(salt32Bit2, 0);

        int rounds = 1 << cost;
        for (int i = 0; i != rounds; i++)        // rounds may be negative if cost is 31
        {
            // state <- ExpandKey(state, 0, key);
            cyclicXorKey(psw);
            processTable(0, 0, P);
            processTable(P[P_SZ - 2], P[P_SZ - 1], S);

            // state <- ExpandKey(state, 0, salt);
            cyclicXorKey(salt);
            processTable(0, 0, P);
            processTable(P[P_SZ - 2], P[P_SZ - 1], S);
        }

        // encrypt magicString 64 times
        return encryptMagicString();
    }

    /**
     * Size of the salt parameter in bytes
     */
    static final int SALT_SIZE_BYTES = 16;

    /**
     * Minimum value of cost parameter, equal to log2(bytes of salt)
     */
    static final int MIN_COST = 4;

    /**
     * Maximum value of cost parameter (31 == 2,147,483,648)
     */
    static final int MAX_COST = 31;

    /**
     * Maximum size of password == max (unrestricted) size of Blowfish key
     */
    // Blowfish spec limits keys to 448bit/56 bytes to ensure all bits of key affect all ciphertext
    // bits, but technically algorithm handles 72 byte keys and most implementations support this.
    static final int MAX_PASSWORD_BYTES = 72;

    /**
     * Converts a character password to bytes incorporating the required trailing zero byte.
     *
     * @param password the password to be encoded.
     * @return a byte representation of the password in UTF8 + trailing zero.
     */
    public static byte[] passwordToByteArray(char[] password)
    {
        return Arrays.append(Strings.toUTF8ByteArray(password), (byte)0);
    }

    /**
     * Calculates the <b>bcrypt</b> hash of an input, passing the password bytes through to the
     * EksBlowfishSetup password schedule unchanged. The bcrypt specification requires the password
     * input to be null-terminated; this overload does not append the terminator, so the caller must
     * supply {@code pwInput} already terminated (for example via {@link #passwordToByteArray(char[])}).
     * Without a trailing 0x00 byte, distinct passwords whose encodings differ only by repetition
     * (e.g. {@code "abc"} and {@code "abcabc"}) collide and produce identical hashes.
     * <p>
     * This implements the raw <b>bcrypt</b> function as defined in the bcrypt specification, not
     * the crypt encoded version implemented in OpenBSD, see {@link OpenBSDBCrypt} for that.
     * </p>
     * @param pwInput    the password bytes (up to 72 bytes) to use for this invocation.
     * @param salt     the 128 bit salt to use for this invocation.
     * @param cost     the bcrypt cost parameter. The cost of the bcrypt function grows as
     *                 <code>2^cost</code>. Legal values are 4..31 inclusive.
     * @return the output of the raw bcrypt operation: a 192 bit (24 byte) hash.
     * @deprecated as a direct replacement use {@link #generate(byte[], byte[], int, boolean)} so
     *             the terminator choice is explicit at the call site &mdash; pass {@code true} to
     *             have the spec-required 0x00 terminator appended (equivalent to feeding
     *             {@code pwInput} through {@link #passwordToByteArray(char[])}), {@code false}
     *             when the supplied bytes already include it. For general password hashing prefer
     *             {@link OpenBSDBCrypt}, which handles termination, salt formatting and the
     *             modular crypt output line; this raw primitive remains available for test-vector
     *             validation and interop with implementations that emit the 24-byte hash directly
     *             (issue #1741).
     */
    public static byte[] generate(byte[] pwInput, byte[] salt, int cost)
    {
        return generate(pwInput, salt, cost, false);
    }

    /**
     * Calculates the <b>bcrypt</b> hash of an input, optionally appending the bcrypt password
     * terminator (a single 0x00 byte) to {@code pwInput} before the EksBlowfishSetup password
     * schedule. For general password hashing use {@link OpenBSDBCrypt} rather than this primitive;
     * this entry point is intended for callers driving the raw bcrypt function against published
     * test vectors or interoperating with another implementation that produces the 24-byte raw
     * hash directly.
     * <p>
     * Setting {@code addTerminator} {@code true} is equivalent to feeding bytes produced by
     * {@link #passwordToByteArray(char[])} and is the right choice for any caller that has not
     * already terminated the input. Setting it {@code false} passes {@code pwInput} through
     * unchanged &mdash; appropriate when the supplied bytes are already terminated, or when
     * reproducing a test vector that fixes the exact input.
     * </p>
     * <p>
     * When {@code pwInput.length} is exactly {@value #MAX_PASSWORD_BYTES} (the bcrypt 72-byte
     * input limit), {@code addTerminator} is ignored and the input is used as-is &mdash; there is
     * no room for an additional byte without exceeding the limit. Two 72-byte inputs sharing a
     * common prefix may therefore collide in the same way an unterminated shorter input does.
     * </p>
     *
     * @param pwInput       the password bytes (up to 72 bytes) to use for this invocation.
     * @param salt          the 128 bit salt to use for this invocation.
     * @param cost          the bcrypt cost parameter. The cost of the bcrypt function grows as
     *                      <code>2^cost</code>. Legal values are 4..31 inclusive.
     * @param addTerminator whether to append the bcrypt password-terminator byte (0x00) to
     *                      {@code pwInput} before the password schedule. Ignored when
     *                      {@code pwInput.length} is exactly 72.
     * @return the output of the raw bcrypt operation: a 192 bit (24 byte) hash.
     */
    public static byte[] generate(byte[] pwInput, byte[] salt, int cost, boolean addTerminator)
    {
        if (pwInput == null || salt == null)
        {
            throw new IllegalArgumentException("pwInput and salt are required");
        }
        if (salt.length != SALT_SIZE_BYTES)
        {
            throw new IllegalArgumentException("BCrypt salt must be 128 bits");
        }
        if (pwInput.length > MAX_PASSWORD_BYTES)
        {
            throw new IllegalArgumentException("BCrypt password must be <= 72 bytes");
        }
        if (cost < MIN_COST || cost > MAX_COST)
        {
            throw new IllegalArgumentException("BCrypt cost must be from 4..31");
        }

        byte[] effective = pwInput;
        if (addTerminator && pwInput.length < MAX_PASSWORD_BYTES)
        {
            effective = Arrays.append(pwInput, (byte)0);
        }

        return new BCrypt().deriveRawKey(cost, salt, effective);
    }

    //====================================
    // OpenSSH bcrypt_pbkdf
    //====================================

    /**
     * Clear text for the OpenSSH bcrypt_pbkdf hash step ("OxychromaticBlowfishSwatDynamite",
     * 32 bytes = 8 32-bit words). Distinct from the OpenBSD MAGIC_STRING used by the password
     * hash above.
     */
    private static final byte[] BCRYPT_PBKDF_MAGIC = Strings.toByteArray("OxychromaticBlowfishSwatDynamite");

    /**
     * Output size, in bytes, of a single OpenSSH {@code bcrypt_hash} block.
     */
    private static final int BCRYPT_PBKDF_HASH_SIZE = 32;

    /**
     * The generic Blowfish encipher operation (16 rounds), updating {@code lr[0]} / {@code lr[1]}
     * in place. Uses the current {@link #P} / {@link #S} state and matches the layout the existing
     * {@link #processTable} fill relies on (output stored as the swapped pair).
     */
    private void encipher(int[] lr)
    {
        int xl = lr[0];
        int xr = lr[1];

        xl ^= P[0];
        for (int i = 1; i < ROUNDS; i += 2)
        {
            xr ^= F(xl) ^ P[i];
            xl ^= F(xr) ^ P[i + 1];
        }
        xr ^= P[ROUNDS + 1];

        lr[0] = xr;
        lr[1] = xl;
    }

    /**
     * OpenSSH {@code Blowfish_stream2word}: read the next big-endian 32-bit word from {@code data},
     * cycling back to the start when the end is reached. {@code offset[0]} carries the cursor.
     */
    private static int streamToWord(byte[] data, int[] offset)
    {
        int word = 0;
        int off = offset[0];
        for (int i = 0; i < 4; i++)
        {
            word = (word << 8) | (data[off] & 0xff);
            off = (off + 1) % data.length;
        }
        offset[0] = off;
        return word;
    }

    /**
     * OpenSSH {@code Blowfish_expandstate}: the salted (eksblowfish) key schedule, with both
     * {@code data} and {@code key} streamed cyclically. Unlike {@link #processTableWithSalt} this
     * accepts an arbitrary-length salt, as bcrypt_pbkdf passes 64-byte SHA-512 outputs.
     */
    private void expandState(byte[] data, byte[] key)
    {
        int[] keyOffset = new int[1];
        for (int i = 0; i < P_SZ; i++)
        {
            P[i] ^= streamToWord(key, keyOffset);
        }

        int[] lr = new int[2];
        int[] dataOffset = new int[1];
        for (int i = 0; i < P_SZ; i += 2)
        {
            lr[0] ^= streamToWord(data, dataOffset);
            lr[1] ^= streamToWord(data, dataOffset);
            encipher(lr);
            P[i] = lr[0];
            P[i + 1] = lr[1];
        }
        for (int i = 0; i < S.length; i += 2)
        {
            lr[0] ^= streamToWord(data, dataOffset);
            lr[1] ^= streamToWord(data, dataOffset);
            encipher(lr);
            S[i] = lr[0];
            S[i + 1] = lr[1];
        }
    }

    /**
     * OpenSSH {@code Blowfish_expand0state}: as {@link #expandState} but with an all-zero data
     * stream, so only the key is mixed into P and the encipher output chains through P and S.
     */
    private void expand0State(byte[] key)
    {
        int[] keyOffset = new int[1];
        for (int i = 0; i < P_SZ; i++)
        {
            P[i] ^= streamToWord(key, keyOffset);
        }

        int[] lr = new int[2];
        for (int i = 0; i < P_SZ; i += 2)
        {
            encipher(lr);
            P[i] = lr[0];
            P[i + 1] = lr[1];
        }
        for (int i = 0; i < S.length; i += 2)
        {
            encipher(lr);
            S[i] = lr[0];
            S[i + 1] = lr[1];
        }
    }

    /**
     * OpenSSH {@code bcrypt_hash}: 64-round eksblowfish setup over the two 64-byte SHA-512 inputs,
     * then 64 ECB encryptions of the 32-byte magic, emitted as little-endian words.
     */
    private byte[] bcryptHash(byte[] sha2pass, byte[] sha2salt)
    {
        initState();
        expandState(sha2salt, sha2pass);
        for (int i = 0; i < 64; i++)
        {
            expand0State(sha2salt);
            expand0State(sha2pass);
        }

        int[] cdata = new int[BCRYPT_PBKDF_HASH_SIZE / 4];
        int[] magicOffset = new int[1];
        for (int i = 0; i < cdata.length; i++)
        {
            cdata[i] = streamToWord(BCRYPT_PBKDF_MAGIC, magicOffset);
        }

        int[] lr = new int[2];
        for (int i = 0; i < 64; i++)
        {
            for (int j = 0; j < cdata.length; j += 2)
            {
                lr[0] = cdata[j];
                lr[1] = cdata[j + 1];
                encipher(lr);
                cdata[j] = lr[0];
                cdata[j + 1] = lr[1];
            }
        }

        byte[] out = new byte[BCRYPT_PBKDF_HASH_SIZE];
        for (int i = 0; i < cdata.length; i++)
        {
            // little-endian, the OpenSSH word swap
            out[4 * i] = (byte)cdata[i];
            out[4 * i + 1] = (byte)(cdata[i] >>> 8);
            out[4 * i + 2] = (byte)(cdata[i] >>> 16);
            out[4 * i + 3] = (byte)(cdata[i] >>> 24);
        }

        Arrays.fill(P, 0);
        Arrays.fill(S, 0);

        return out;
    }

    /**
     * The OpenSSH {@code bcrypt_pbkdf} password-based key derivation function, as used to protect
     * the {@code openssh-key-v1} private key format (kdfname {@code "bcrypt"}). It layers SHA-512
     * over a 32-byte {@code bcrypt_hash} primitive and distributes the output non-linearly; it is
     * <b>not</b> interchangeable with PBKDF2-over-bcrypt or with the OpenBSD password hash produced
     * by {@link #generate(byte[], byte[], int, boolean)} / {@link OpenBSDBCrypt}.
     *
     * @param password     the passphrase bytes (the OpenSSH client uses the raw UTF-8 bytes, with
     *                     no trailing NUL).
     * @param salt         the salt taken from the key's kdfoptions; must be non-empty.
     * @param rounds       the iteration count from the key's kdfoptions; must be at least 1.
     * @param outputLength the number of key bytes to derive (the cipher key length plus IV length);
     *                     must be between 1 and 1024 inclusive.
     * @return {@code outputLength} derived key bytes.
     */
    public static byte[] pbkdfGenerate(byte[] password, byte[] salt, int rounds, int outputLength)
    {
        if (password == null || salt == null)
        {
            throw new IllegalArgumentException("password and salt are required");
        }
        if (salt.length == 0)
        {
            throw new IllegalArgumentException("salt must not be empty");
        }
        if (rounds < 1)
        {
            throw new IllegalArgumentException("rounds must be at least 1");
        }
        if (outputLength < 1 || outputLength > BCRYPT_PBKDF_HASH_SIZE * BCRYPT_PBKDF_HASH_SIZE)
        {
            throw new IllegalArgumentException("outputLength must be from 1 to 1024");
        }

        SHA512Digest sha512 = new SHA512Digest();

        byte[] sha2pass = new byte[64];
        sha512.update(password, 0, password.length);
        sha512.doFinal(sha2pass, 0);

        byte[] sha2salt = new byte[64];
        byte[] out = new byte[BCRYPT_PBKDF_HASH_SIZE];
        byte[] tmpout = new byte[BCRYPT_PBKDF_HASH_SIZE];
        byte[] countsalt = new byte[4];
        byte[] key = new byte[outputLength];

        BCrypt bcrypt = new BCrypt();

        int stride = (outputLength + BCRYPT_PBKDF_HASH_SIZE - 1) / BCRYPT_PBKDF_HASH_SIZE;
        int amt = (outputLength + stride - 1) / stride;

        int keylen = outputLength;
        for (int count = 1; keylen > 0; count++)
        {
            Pack.intToBigEndian(count, countsalt, 0);

            // first round: salt is the supplied salt followed by the block counter
            sha512.update(salt, 0, salt.length);
            sha512.update(countsalt, 0, 4);
            sha512.doFinal(sha2salt, 0);

            byte[] hash = bcrypt.bcryptHash(sha2pass, sha2salt);
            System.arraycopy(hash, 0, out, 0, BCRYPT_PBKDF_HASH_SIZE);
            System.arraycopy(hash, 0, tmpout, 0, BCRYPT_PBKDF_HASH_SIZE);

            for (int i = 1; i < rounds; i++)
            {
                // subsequent rounds: salt is the previous output
                sha512.update(tmpout, 0, BCRYPT_PBKDF_HASH_SIZE);
                sha512.doFinal(sha2salt, 0);

                hash = bcrypt.bcryptHash(sha2pass, sha2salt);
                System.arraycopy(hash, 0, tmpout, 0, BCRYPT_PBKDF_HASH_SIZE);
                for (int j = 0; j < BCRYPT_PBKDF_HASH_SIZE; j++)
                {
                    out[j] ^= tmpout[j];
                }
            }

            // pbkdf2 deviation: output the key material non-linearly
            amt = Math.min(amt, keylen);
            int i;
            for (i = 0; i < amt; i++)
            {
                int dest = i * stride + (count - 1);
                if (dest >= outputLength)
                {
                    break;
                }
                key[dest] = out[i];
            }
            keylen -= i;
        }

        Arrays.fill(sha2pass, (byte)0);
        Arrays.fill(sha2salt, (byte)0);
        Arrays.fill(out, (byte)0);
        Arrays.fill(tmpout, (byte)0);

        return key;
    }
}
