using System;

using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Crypto.Generators
{
    /**
     * 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 sealed class BCrypt
    {
        // magic String "OrpheanBeholderScryDoubt" is used as clear text for encryption
        private static readonly uint[] MAGIC_STRING =
        {
            0x4F727068, 0x65616E42, 0x65686F6C,
            0x64657253, 0x63727944, 0x6F756274
        };

        internal const int MAGIC_STRING_LENGTH = 6;

        private static readonly uint[]
            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 const int ROUNDS = 16;
        private const int SBOX_SK = 256;
        private const int SBOX_SK2 = SBOX_SK * 2;
        private const int SBOX_SK3 = SBOX_SK * 3;
        private const int P_SZ = ROUNDS + 2;

        private readonly uint[] S;    // the s-boxes
        private readonly uint[] P;    // the p-array

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

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

        private uint F(uint 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(uint xl, uint xr, uint[] 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;

                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()
        {
            Array.Copy(KS0, 0, S, 0, SBOX_SK);
            Array.Copy(KS1, 0, S, SBOX_SK, SBOX_SK);
            Array.Copy(KS2, 0, S, SBOX_SK2, SBOX_SK);
            Array.Copy(KS3, 0, S, SBOX_SK3, SBOX_SK);

            Array.Copy(KP, 0, P, 0, P_SZ);
        }

        /*
         * XOR P with key cyclic.
         * This is the first part of ExpandKey function
         */
        private 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
                uint data = 0x0000000;
                for (int j = 0; j < 4; j++)
                {
                    // create a 32 bit block
                    data = (data << 8) | key[keyIndex];

                    // 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()
        {
            uint[] 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)
                {
                    uint left = text[j];
                    uint 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.UInt32_To_BE(text, result, 0);
            Array.Clear(text, 0, text.Length);
            Array.Clear(P, 0, P.Length);
            Array.Clear(S, 0, S.Length);

            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(uint[] table, uint[] salt32Bit, uint iv1, uint iv2)
        {
            uint xl = iv1 ^ salt32Bit[0];
            uint xr = iv2 ^ salt32Bit[1];

            uint yl;
            uint 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];

                table[s] = xr;
                table[s + 1] = xl;

                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;
                table[s + 3] = yl;

                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 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 ArgumentException("Illegal cost factor: 4 - 31 expected.", "cost");

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

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

            uint[] salt32Bit = new uint[4]; // holds 16 byte salt
            Pack.BE_To_UInt32(salt, 0, salt32Bit);

            uint[] salt32Bit2 = new uint[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);
            Array.Clear(salt32Bit, 0, salt32Bit.Length);
            ProcessTableWithSalt(S, salt32Bit2, P[P.Length - 2], P[P.Length - 1]);
            Array.Clear(salt32Bit2, 0, salt32Bit2.Length);

            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
         */
        internal const int SALT_SIZE_BYTES = 16;

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

        /**
         * Maximum value of cost parameter (31 == 2,147,483,648)
         */
        internal const 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.
        internal const 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), 0);
        }

        /**
         * Calculates the <b>bcrypt</b> hash of a password.
         * <p>
         * This implements the raw <b>bcrypt</b> function as defined in the bcrypt specification, not
         * the crypt encoded version implemented in OpenBSD.
         * </p>
         * @param password 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.
         */
        public static byte[] Generate(byte[] password, byte[] salt, int cost)
        {
            if (password == null)
                throw new ArgumentNullException("password");
            if (password.Length > MAX_PASSWORD_BYTES)
                throw new ArgumentException("BCrypt password must be <= 72 bytes", "password");
            if (salt == null)
                throw new ArgumentNullException("salt");
            if (salt.Length != SALT_SIZE_BYTES)
                throw new ArgumentException("BCrypt salt must be 128 bits", "salt");
            if (cost < MIN_COST || cost > MAX_COST)
                throw new ArgumentException("BCrypt cost must be from 4..31", "cost");

            return new BCrypt().DeriveRawKey(cost, salt, password);
        }
    }
}
