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浅谈加密算法BCrypt

@Test
    public void contextLoads() {
        String password = "12345";
        String hashed = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed);
 
        String hashed01 = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed01);
 
        String hashed02 = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed02);
 
 
        String hashed03 = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed03);
 
 
        String hashed04 = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed04);
 
        String hashed05 = BCrypt.hashpw(password, BCrypt.gensalt());
        System.out.println(hashed05);
// gensalt's log_rounds parameter determines the complexity
// the work factor is 2**log_rounds, and the default is 10
        String hashed2 = BCrypt.hashpw(password, BCrypt.gensalt(12));
 
// Check that an unencrypted password matches one that has
// previously been hashed
        String candidate = "12345";
 
        if (BCrypt.checkpw(candidate, hashed))
            System.out.println("It matches");
        else
            System.out.println("It does not match");
    }

　　在最新的Springboot secrity包中，登录加密的方式是BCrypt

当然，也可以直接下载BCrypt的jar包，进行加密和判断输入是否一致

<dependency>
    <groupId>org.mindrot</groupId>
    <artifactId>jbcrypt</artifactId>
    <version>0.4</version>
</dependency>

　　也可以到官网 http://www.mindrot.org/projects/jBCrypt/

ok，依赖的事情说完时候，可以用上述测试代码查看一下，加密之后的字符串，运行了对于字符串12345的加密，结果如下

其中：$是分割符，无意义；2a是bcrypt加密版本号；10是cost的值；而后的前22位是salt值；再然后的字符串就是密码的密文了。

这块代码的格式拼接可以查看gensalt()方法源码：

从最下面往上看，返回log_rounds = 10，这就是版本号；

下一步，返回版本号和引用对象；

下一步，rs指向一个StringBuffer对象，先不管三七二十一，添加 $2a$

再判断 log_rounds 的值，小于10的按照0处理，大于30的抛出异常

11-29之间（包含），在 $2a$ 先添加 log_rounds 的值，再添加 $ , 再添加 base64位的加密

这一切之后，返回了salt值

public static String hashpw(String password, String salt) {
        char minor = 0;
        int off = false;
        StringBuffer rs = new StringBuffer();
        if (salt.charAt(0) == '$' && salt.charAt(1) == '2') {
            byte off;
            if (salt.charAt(2) == '$') {
                off = 3;
            } else {
                minor = salt.charAt(2);
                if (minor != 'a' || salt.charAt(3) != '$') {
                    throw new IllegalArgumentException("Invalid salt revision");
                }
 
                off = 4;
            }
 
            if (salt.charAt(off + 2) > '$') {
                throw new IllegalArgumentException("Missing salt rounds");
            } else {
                int rounds = Integer.parseInt(salt.substring(off, off + 2));
                String real_salt = salt.substring(off + 3, off + 25);
 
                byte[] passwordb;
                try {
                    passwordb = (password + (minor >= 'a' ? "\u0000" : "")).getBytes("UTF-8");
                } catch (UnsupportedEncodingException var12) {
                    throw new AssertionError("UTF-8 is not supported");
                }
 
                byte[] saltb = decode_base64(real_salt, 16);
                BCrypt B = new BCrypt();
                byte[] hashed = B.crypt_raw(passwordb, saltb, rounds, (int[])((int[])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)");
                } else {
                    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();
                }
            }
        } else {
            throw new IllegalArgumentException("Invalid salt version");
        }
    }

　　之后加密计算返回加密后的字符串，方法名是hashpw，具体实现有点长，复制了代码如上

具体的encode_base64加密和解密，和我以前了解的不太一致

以前的了解是单个字符串进行base64加密和解密，可逆 https://www.cnblogs.com/qianjinyan/p/9541368.html

而此时是如下

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//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
 
package org.mindrot.jbcrypt;
 
import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;
 
public class BCrypt {
    private static final int GENSALT_DEFAULT_LOG2_ROUNDS = 10;
    private static final int BCRYPT_SALT_LEN = 16;
    private static final int BLOWFISH_NUM_ROUNDS = 16;
    private static final int[] P_orig = new int[]{608135816, -2052912941, 320440878, 57701188, -1542899678, 698298832, 137296536, -330404727, 1160258022, 953160567, -1101764913, 887688300, -1062458953, -914599715, 1065670069, -1253635817, -1843997223, -1988494565};
    private static final int[] S_orig = new int[]{-785314906, -1730169428, 805139163, -803545161, -1193168915, 1780907670, -1166241723, -248741991, 614570311, -1282315017, 134345442, -2054226922, 1667834072, 1901547113, -1537671517, -191677058, 227898511, 1921955416, 1904987480, -2112533778, 2069144605, -1034266187, -1674521287, 720527379, -976113629, 677414384, -901678824, -1193592593, -1904616272, 1614419982, 1822297739, -1340175810, -686458943, -1120842969, 2024746970, 1432378464, -430627341, -1437226092, 1464375394, 1676153920, 1439316330, 715854006, -1261675468, 289532110, -1588296017, 2087905683, -1276242927, 1668267050, 732546397, 1947742710, -832815594, -1685613794, -1344882125, 1814351708, 2050118529, 680887927, 999245976, 1800124847, -994056165, 1713906067, 1641548236, -81679983, 1216130144, 1575780402, -276538019, -377129551, -601480446, -345695352, 596196993, -745100091, 258830323, -2081144263, 772490370, -1534844924, 1774776394, -1642095778, 566650946, -152474470, 1728879713, -1412200208, 1783734482, -665571480, -1777359064, -1420741725, 1861159788, 326777828, -1170476976, 2130389656, -1578015459, 967770486, 1724537150, -2109534584, -1930525159, 1164943284, 2105845187, 998989502, -529566248, -2050940813, 1075463327, 1455516326, 1322494562, 910128902, 469688178, 1117454909, 936433444, -804646328, -619713837, 1240580251, 122909385, -2137449605, 634681816, -152510729, -469872614, -1233564613, -1754472259, 79693498, -1045868618, 1084186820, 1583128258, 426386531, 1761308591, 1047286709, 322548459, 995290223, 1845252383, -1691314900, -863943356, -1352745719, -1092366332, -567063811, 1712269319, 422464435, -1060394921, 1170764815, -771006663, -1177289765, 1434042557, 442511882, -694091578, 1076654713, 1738483198, -81812532, -1901729288, -617471240, 1014306527, -43947243, 793779912, -1392160085, 842905082, -48003232, 1395751752, 1040244610, -1638115397, -898659168, 445077038, -552113701, -717051658, 679411651, -1402522938, -1940957837, 1767581616, 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146436021, 1461446943, -224990101, 705550613, -1235000031, -407242314, -13368018, -981117340, 1404054877, -1449160799, 146425753, 1854211946, 1266315497, -1246549692, -613086930, -1004984797, -1385257296, 1235738493, -1662099272, -1880247706, -324367247, 1771706367, 1449415276, -1028546847, 422970021, 1963543593, -1604775104, -468174274, 1062508698, 1531092325, 1804592342, -1711849514, -1580033017, -269995787, 1294809318, -265986623, 1289560198, -2072974554, 1669523910, 35572830, 157838143, 1052438473, 1016535060, 1802137761, 1753167236, 1386275462, -1214491899, -1437595849, 1040679964, 2145300060, -1904392980, 1461121720, -1338320329, -263189491, -266592508, 33600511, -1374882534, 1018524850, 629373528, -603381315, -779021319, 2091462646, -1808644237, 586499841, 988145025, 935516892, -927631820, -1695294041, -1455136442, 265290510, -322386114, -1535828415, -499593831, 1005194799, 847297441, 406762289, 1314163512, 1332590856, 1866599683, -167115585, 750260880, 613907577, 1450815602, -1129346641, -560302305, -644675568, -1282691566, -590397650, 1427272223, 778793252, 1343938022, -1618686585, 2052605720, 1946737175, -1130390852, -380928628, -327488454, -612033030, 1661551462, -1000029230, -283371449, 840292616, -582796489, 616741398, 312560963, 711312465, 1351876610, 322626781, 1910503582, 271666773, -2119403562, 1594956187, 70604529, -677132437, 1007753275, 1495573769, -225450259, -1745748998, -1631928532, 504708206, -2031925904, -353800271, -2045878774, 1514023603, 1998579484, 1312622330, 694541497, -1712906993, -2143385130, 1382467621, 776784248, -1676627094, -971698502, -1797068168, -1510196141, 503983604, -218673497, 907881277, 423175695, 432175456, 1378068232, -149744970, -340918674, -356311194, -474200683, -1501837181, -1317062703, 26017576, -1020076561, -1100195163, 1700274565, 1756076034, -288447217, -617638597, 720338349, 1533947780, 354530856, 688349552, -321042571, 1637815568, 332179504, -345916010, 53804574, -1442618417, -1250730864, 1282449977, 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-989067582, 1510255612, -2146710820, -1639679442, -1018874748, -36346107, 236887753, -613164077, 274041037, 1734335097, -479771840, -976997275, 1899903192, 1026095262, -244449504, 356393447, -1884275382, -421290197, -612127241, -381855128, -1803468553, -162781668, -1805047500, 1091903735, 1979897079, -1124832466, -727580568, -737663887, 857797738, 1136121015, 1342202287, 507115054, -1759230650, 337727348, -1081374656, 1301675037, -1766485585, 1895095763, 1721773893, -1078195732, 62756741, 2142006736, 835421444, -1762973773, 1442658625, -635090970, -1412822374, 676362277, 1392781812, 170690266, -373920261, 1759253602, -683120384, 1745797284, 664899054, 1329594018, -393761396, -1249058810, 2062866102, -1429332356, -751345684, -830954599, 1080764994, 553557557, -638351943, -298199125, 991055499, 499776247, 1265440854, 648242737, -354183246, 980351604, -581221582, 1749149687, -898096901, -83167922, -654396521, 1161844396, -1169648345, 1431517754, 545492359, -26498633, -795437749, 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    private static final int[] bf_crypt_ciphertext = new int[]{1332899944, 1700884034, 1701343084, 1684370003, 1668446532, 1869963892};
    private static final char[] base64_code = new char[]{'.', '/', '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'};
    private static final byte[] index_64 = new byte[]{-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};
    private int[] P;
    private int[] S;
 
    public BCrypt() {
    }
 
    private static String encode_base64(byte[] d, int len) throws IllegalArgumentException {
        int off = 0;
        StringBuffer rs = new StringBuffer();
        if (len > 0 && len <= d.length) {
            while(off < len) {
                int c1 = d[off++] & 255;
                rs.append(base64_code[c1 >> 2 & 63]);
                c1 = (c1 & 3) << 4;
                if (off >= len) {
                    rs.append(base64_code[c1 & 63]);
                    break;
                }
 
                int c2 = d[off++] & 255;
                c1 |= c2 >> 4 & 15;
                rs.append(base64_code[c1 & 63]);
                c1 = (c2 & 15) << 2;
                if (off >= len) {
                    rs.append(base64_code[c1 & 63]);
                    break;
                }
 
                c2 = d[off++] & 255;
                c1 |= c2 >> 6 & 3;
                rs.append(base64_code[c1 & 63]);
                rs.append(base64_code[c2 & 63]);
            }
 
            return rs.toString();
        } else {
            throw new IllegalArgumentException("Invalid len");
        }
    }
 
    private static byte char64(char x) {
        return x >= 0 && x <= index_64.length ? index_64[x] : -1;
    }
 
    private static byte[] decode_base64(String s, int maxolen) throws IllegalArgumentException {
        StringBuffer rs = new StringBuffer();
        int off = 0;
        int slen = s.length();
        int olen = 0;
        if (maxolen <= 0) {
            throw new IllegalArgumentException("Invalid maxolen");
        } else {
            while(off < slen - 1 && olen < maxolen) {
                byte c1 = char64(s.charAt(off++));
                byte c2 = char64(s.charAt(off++));
                if (c1 == -1 || c2 == -1) {
                    break;
                }
 
                byte o = (byte)(c1 << 2);
                o = (byte)(o | (c2 & 48) >> 4);
                rs.append((char)o);
                ++olen;
                if (olen >= maxolen || off >= slen) {
                    break;
                }
 
                byte c3 = char64(s.charAt(off++));
                if (c3 == -1) {
                    break;
                }
 
                o = (byte)((c2 & 15) << 4);
                o = (byte)(o | (c3 & 60) >> 2);
                rs.append((char)o);
                ++olen;
                if (olen >= maxolen || off >= slen) {
                    break;
                }
 
                byte c4 = char64(s.charAt(off++));
                o = (byte)((c3 & 3) << 6);
                o |= c4;
                rs.append((char)o);
                ++olen;
            }
 
            byte[] ret = new byte[olen];
 
            for(off = 0; off < olen; ++off) {
                ret[off] = (byte)rs.charAt(off);
            }
 
            return ret;
        }
    }
 
    private final void encipher(int[] lr, int off) {
        int l = lr[off];
        int r = lr[off + 1];
        l ^= this.P[0];
 
        int n;
        for(int i = 0; i <= 14; l ^= n ^ this.P[i]) {
            n = this.S[l >> 24 & 255];
            n += this.S[256 | l >> 16 & 255];
            n ^= this.S[512 | l >> 8 & 255];
            n += this.S[768 | l & 255];
            ++i;
            r ^= n ^ this.P[i];
            n = this.S[r >> 24 & 255];
            n += this.S[256 | r >> 16 & 255];
            n ^= this.S[512 | r >> 8 & 255];
            n += this.S[768 | r & 255];
            ++i;
        }
 
        lr[off] = r ^ this.P[17];
        lr[off + 1] = l;
    }
 
    private static int streamtoword(byte[] data, int[] offp) {
        int word = 0;
        int off = offp[0];
 
        for(int i = 0; i < 4; ++i) {
            word = word << 8 | data[off] & 255;
            off = (off + 1) % data.length;
        }
 
        offp[0] = off;
        return word;
    }
 
    private void init_key() {
        this.P = (int[])((int[])P_orig.clone());
        this.S = (int[])((int[])S_orig.clone());
    }
 
    private void key(byte[] key) {
        int[] koffp = new int[]{0};
        int[] lr = new int[]{0, 0};
        int plen = this.P.length;
        int slen = this.S.length;
 
        int i;
        for(i = 0; i < plen; ++i) {
            this.P[i] ^= streamtoword(key, koffp);
        }
 
        for(i = 0; i < plen; i += 2) {
            this.encipher(lr, 0);
            this.P[i] = lr[0];
            this.P[i + 1] = lr[1];
        }
 
        for(i = 0; i < slen; i += 2) {
            this.encipher(lr, 0);
            this.S[i] = lr[0];
            this.S[i + 1] = lr[1];
        }
 
    }
 
    private void ekskey(byte[] data, byte[] key) {
        int[] koffp = new int[]{0};
        int[] doffp = new int[]{0};
        int[] lr = new int[]{0, 0};
        int plen = this.P.length;
        int slen = this.S.length;
 
        int i;
        for(i = 0; i < plen; ++i) {
            this.P[i] ^= streamtoword(key, koffp);
        }
 
        for(i = 0; i < plen; i += 2) {
            lr[0] ^= streamtoword(data, doffp);
            lr[1] ^= streamtoword(data, doffp);
            this.encipher(lr, 0);
            this.P[i] = lr[0];
            this.P[i + 1] = lr[1];
        }
 
        for(i = 0; i < slen; i += 2) {
            lr[0] ^= streamtoword(data, doffp);
            lr[1] ^= streamtoword(data, doffp);
            this.encipher(lr, 0);
            this.S[i] = lr[0];
            this.S[i + 1] = lr[1];
        }
 
    }
 
    public byte[] crypt_raw(byte[] password, byte[] salt, int log_rounds, int[] cdata) {
        int clen = cdata.length;
        if (log_rounds >= 4 && log_rounds <= 30) {
            int rounds = 1 << log_rounds;
            if (salt.length != 16) {
                throw new IllegalArgumentException("Bad salt length");
            } else {
                this.init_key();
                this.ekskey(salt, password);
 
                int i;
                for(i = 0; i != rounds; ++i) {
                    this.key(password);
                    this.key(salt);
                }
 
                int j;
                for(i = 0; i < 64; ++i) {
                    for(j = 0; j < clen >> 1; ++j) {
                        this.encipher(cdata, j << 1);
                    }
                }
 
                byte[] ret = new byte[clen * 4];
                i = 0;
 
                for(j = 0; i < clen; ++i) {
                    ret[j++] = (byte)(cdata[i] >> 24 & 255);
                    ret[j++] = (byte)(cdata[i] >> 16 & 255);
                    ret[j++] = (byte)(cdata[i] >> 8 & 255);
                    ret[j++] = (byte)(cdata[i] & 255);
                }
 
                return ret;
            }
        } else {
            throw new IllegalArgumentException("Bad number of rounds");
        }
    }
 
    public static String hashpw(String password, String salt) {
        char minor = 0;
        int off = false;
        StringBuffer rs = new StringBuffer();
        if (salt.charAt(0) == '$' && salt.charAt(1) == '2') {
            byte off;
            if (salt.charAt(2) == '$') {
                off = 3;
            } else {
                minor = salt.charAt(2);
                if (minor != 'a' || salt.charAt(3) != '$') {
                    throw new IllegalArgumentException("Invalid salt revision");
                }
 
                off = 4;
            }
 
            if (salt.charAt(off + 2) > '$') {
                throw new IllegalArgumentException("Missing salt rounds");
            } else {
                int rounds = Integer.parseInt(salt.substring(off, off + 2));
                String real_salt = salt.substring(off + 3, off + 25);
 
                byte[] passwordb;
                try {
                    passwordb = (password + (minor >= 'a' ? "\u0000" : "")).getBytes("UTF-8");
                } catch (UnsupportedEncodingException var12) {
                    throw new AssertionError("UTF-8 is not supported");
                }
 
                byte[] saltb = decode_base64(real_salt, 16);
                BCrypt B = new BCrypt();
                byte[] hashed = B.crypt_raw(passwordb, saltb, rounds, (int[])((int[])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)");
                } else {
                    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();
                }
            }
        } else {
            throw new IllegalArgumentException("Invalid salt version");
        }
    }
 
    public static String gensalt(int log_rounds, SecureRandom random) {
        StringBuffer rs = new StringBuffer();
        byte[] rnd = new byte[16];
        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)");
        } else {
            rs.append(Integer.toString(log_rounds));
            rs.append("$");
            rs.append(encode_base64(rnd, rnd.length));
            return rs.toString();
        }
    }
 
    public static String gensalt(int log_rounds) {
        return gensalt(log_rounds, new SecureRandom());
    }
 
    public static String gensalt() {
        return gensalt(10);
    }
 
    public static boolean checkpw(String plaintext, String hashed) {
        byte[] hashed_bytes;
        byte[] try_bytes;
        try {
            String try_pw = hashpw(plaintext, hashed);
            hashed_bytes = hashed.getBytes("UTF-8");
            try_bytes = try_pw.getBytes("UTF-8");
        } catch (UnsupportedEncodingException var6) {
            return false;
        }
 
        if (hashed_bytes.length != try_bytes.length) {
            return false;
        } else {
            byte ret = 0;
 
            for(int i = 0; i < try_bytes.length; ++i) {
                ret = (byte)(ret | hashed_bytes[i] ^ try_bytes[i]);
            }
 
            return ret == 0;
        }
    }
}　　