系统安全-主流密码加密算法BCrypt 和PBKDF2详解

1. BCrypt 加密算法详解

1.1 技术原理

• Bcrypt 是一种密码哈希算法，而非对称或分组加密算法。BCrypt 基于 Blowfish 对称分组密码变形而来，专用于密码存储。
• BCrypt 的核心机制是：对用户密码进行加盐（salt）后，再进行多次哈希迭代，从而生成最终密文。其“工作因子”（cost factor）可配置，决定了迭代次数，计算成本随因子指数级增长。
• BCrypt 每次哈希时会自动生成一个随机盐，并将盐值嵌入到最终密文中，验证时从密文提取盐，与用户输入重新哈希比对。

1.2 优缺点

优点：

• 抗暴力破解：通过可调工作因子，哈希过程变慢，增加攻击成本。
• 自动加盐：每次哈希结果不同，有效防止彩虹表攻击。
• 成熟可靠：经过多年实战检验，社区支持广泛。
  缺点：
• 计算资源消耗高：迭代次数多，对服务器性能有影响。
• 内存消耗固定：不像 Scrypt 等算法，BCrypt 内存消耗固定，面对 GPU/ASIC 等硬件加速攻击时防御力相对弱。

1.3 适用场景

• Web应用密码存储：如用户注册/登录密码哈希，是 Spring Security 等框架的默认选择。
• 需要抗暴力破解的密码验证场景：尤其适合高安全性要求的应用。

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代码实现

实现了BCrypt加密算法，用于密码哈希。主要功能包括：
密码加密：crypt方法对密码和盐进行多轮加密。
哈希生成：hashpw生成包含盐和哈希的完整字符串。
盐生成：gensalt生成随机盐值。
密码验证：checkpw比对明文密码与哈希是否匹配。
使用Blowfish加密和Base64编码，支持自定义轮数增强安全性

import cn.hutool.core.util.CharsetUtil;
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, 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-1549095958, -613658859, -87339056, -951913406, -278217803, 1699691293, 1103962373, -669091426, -2038084153, -464828566, 1031889488, -815619598, 1535977030, -58162272, -1043876189, 2132092099, 1774941330, 1199868427, 1452454533, 157007616, -1390851939, 342012276, 595725824, 1480756522, 206960106, 497939518, 591360097, 863170706, -1919713727, -698356495, 1814182875, 2094937945, -873565088, 1082520231, -831049106, -1509457788, 435703966, -386934699, 1641649973, -1452693590, -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, 1437099964, -1592419752, -861329053, -1713251533, -1507177898, 1060185593, 1593081372, -1876348548, -34019326, 69676912, -2135222948, 86519011, -1782508216, -456757982, 1220612927, -955283748, 133810670, 1090789135, 1078426020, 1569222167, 845107691, -711212847, -222510705, 1091646820, 628848692, 1613405280, -537335645, 526609435, 236106946, 48312990, -1352249391, -892239595, 1797494240, 859738849, 992217954, -289490654, -2051890674, -424014439, -562951028, 765654824, -804095931, -1783130883, 1685915746, -405998096, 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-1932175983, -922558900, -1190417183, -1149106736, 296247880, 1970579870, -1216407114, -525738999, 1714227617, -1003338189, -396747006, 166772364, 1251581989, 493813264, 448347421, 195405023, -1584991729, 677966185, -591930749, 1463355134, -1578971493, 1338867538, 1343315457, -1492745222, -1610435132, 233230375, -1694987225, 2000651841, -1017099258, 1638401717, -266896856, -1057650976, 6314154, 819756386, 300326615, 590932579, 1405279636, -1027467724, -1144263082, -1866680610, -335774303, -833020554, 1862657033, 1266418056, 963775037, 2089974820, -2031914401, 1917689273, 448879540, -744572676, -313240200, 150775221, -667058989, 1303187396, 508620638, -1318983944, -1568336679, 1817252668, 1876281319, 1457606340, 908771278, -574175177, -677760460, -1838972398, 1729034894, 1080033504, 976866871, -738527793, -1413318857, 1522871579, 1555064734, 1336096578, -746444992, -1715692610, -720269667, -1089506539, -701686658, -956251013, -1215554709, 564236357, -1301368386, 1781952180, 1464380207, -1131123079, -962365742, 1699332808, 1393555694, 1183702653, -713881059, 1288719814, 691649499, -1447410096, -1399511320, -1101077756, -1577396752, 1781354906, 1676643554, -1702433246, -1064713544, 1126444790, -1524759638, -1661808476, -2084544070, -1679201715, -1880812208, -1167828010, 673620729, -1489356063, 1269405062, -279616791, -953159725, -145557542, 1057255273, 2012875353, -2132498155, -2018474495, -1693849939, 993977747, -376373926, -1640704105, 753973209, 36408145, -1764381638, 25011837, -774947114, 2088578344, 530523599, -1376601957, 1524020338, 1518925132, -534139791, -535190042, 1202760957, -309069157, -388774771, 674977740, -120232407, 2031300136, 2019492241, -311074731, -141160892, -472686964, 352677332, -1997247046, 60907813, 90501309, -1007968747, 1016092578, -1759044884, -1455814870, 457141659, 509813237, -174299397, 652014361, 1966332200, -1319764491, 55981186, -1967506245, 676427537, -1039476232, -1412673177, -861040033, 1307055953, 942726286, 933058658, -1826555503, -361066302, -79791154, 1361170020, 2001714738, -1464409218, -1020707514, 1222529897, 1679025792, -1565652976, -580013532, 1770335741, 151462246, -1281735158, 1682292957, 1483529935, 471910574, 1539241949, 458788160, -858652289, 1807016891, -576558466, 978976581, 1043663428, -1129001515, 1927990952, -94075717, -1922690386, -1086558393, -761535389, 1412390302, -1362987237, -162634896, 1947078029, -413461673, -126740879, -1353482915, 1077988104, 1320477388, 886195818, 18198404, -508558296, -1785185763, 112762804, -831610808, 1866414978, 891333506, 18488651, 661792760, 1628790961, -409780260, -1153795797, 876946877, -1601685023, 1372485963, 791857591, -1608533303, -534984578, -1127755274, -822013501, -1578587449, 445679433, -732971622, -790962485, -720709064, 54117162, -963561881, -1913048708, -525259953, -140617289, 1140177722, -220915201, 668550556, -1080614356, 367459370, 261225585, -1684794075, -85617823, -826893077, -1029151655, 314222801, -1228863650, -486184436, 282218597, -888953790, -521376242, 379116347, 1285071038, 846784868, -1625320142, -523005217, -744475605, -1989021154, 453669953, 1268987020, -977374944, -1015663912, -550133875, -1684459730, -435458233, 266596637, -447948204, 517658769, -832407089, -851542417, 370717030, -47440635, -2070949179, -151313767, -182193321, -1506642397, -1817692879, 1456262402, -1393524382, 1517677493, 1846949527, -1999473716, -560569710, -2118563376, 1280348187, 1908823572, -423180355, 846861322, 1172426758, -1007518822, -911584259, 1655181056, -1155153950, 901632758, 1897031941, -1308360158, -1228157060, -847864789, 1393639104, 373351379, 950779232, 625454576, -1170726756, -146354570, 2007998917, 544563296, -2050228658, -1964470824, 2058025392, 1291430526, 424198748, 50039436, 29584100, -689184263, -1865090967, -1503863136, 1057563949, -1039604065, -1219600078, -831004069, 1469046755, 985887462};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;StringBuilder rs = new StringBuilder();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 > index_64.length ? -1 : index_64[x];}private static byte[] decodeBase64(String s, int maxolen) throws IllegalArgumentException {StringBuilder rs = new StringBuilder();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 = (byte)(o | c4);rs.append((char)o);++olen;}byte[] ret = new byte[olen];for(int var15 = 0; var15 < olen; ++var15) {ret[var15] = (byte)rs.charAt(var15);}return ret;}}private 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[])P_orig.clone();this.S = (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;for(int i = 0; i < plen; ++i) {this.P[i] ^= streamToWord(key, koffp);}for(int var7 = 0; var7 < plen; var7 += 2) {this.encipher(lr, 0);this.P[var7] = lr[0];this.P[var7 + 1] = lr[1];}for(int var8 = 0; var8 < slen; var8 += 2) {this.encipher(lr, 0);this.S[var8] = lr[0];this.S[var8 + 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;for(int i = 0; i < plen; ++i) {this.P[i] ^= streamToWord(key, koffp);}for(int var9 = 0; var9 < plen; var9 += 2) {lr[0] ^= streamToWord(data, doffp);lr[1] ^= streamToWord(data, doffp);this.encipher(lr, 0);this.P[var9] = lr[0];this.P[var9 + 1] = lr[1];}for(int var10 = 0; var10 < slen; var10 += 2) {lr[0] ^= streamToWord(data, doffp);lr[1] ^= streamToWord(data, doffp);this.encipher(lr, 0);this.S[var10] = lr[0];this.S[var10 + 1] = lr[1];}}public byte[] crypt(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);for(int i = 0; i != rounds; ++i) {this.key(password);this.key(salt);}for(int var10 = 0; var10 < 64; ++var10) {for(int j = 0; j < clen >> 1; ++j) {this.encipher(cdata, j << 1);}}byte[] ret = new byte[clen * 4];int var11 = 0;for(int j = 0; var11 < clen; ++var11) {ret[j++] = (byte)(cdata[var11] >> 24 & 255);ret[j++] = (byte)(cdata[var11] >> 16 & 255);ret[j++] = (byte)(cdata[var11] >> 8 & 255);ret[j++] = (byte)(cdata[var11] & 255);}return ret;}} else {throw new IllegalArgumentException("Bad number of rounds");}}public static String hashpw(String password) {return hashpw(password, gensalt());}public static String hashpw(String password, String salt) {char minor = 0;StringBuilder rs = new StringBuilder();if (salt.charAt(0) == '$' && salt.charAt(1) == '2') {int off;if (salt.charAt(2) == '$') {off = 3;} else {minor = salt.charAt(2);if (minor != 'a' && minor != 'x' && minor != 'y' && minor != 'b' || 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 = (password + (minor >= 'a' ? "\u0000" : "")).getBytes(CharsetUtil.CHARSET_UTF_8);byte[] saltb = decodeBase64(real_salt, 16);BCrypt bcrypt = new BCrypt();byte[] hashed = bcrypt.crypt(passwordb, saltb, rounds, (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(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) {StringBuilder rs = new StringBuilder();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(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) {String try_pw;try {try_pw = hashpw(plaintext, hashed);} catch (Exception var7) {return false;}byte[] hashed_bytes = hashed.getBytes(CharsetUtil.CHARSET_UTF_8);byte[] try_bytes = try_pw.getBytes(CharsetUtil.CHARSET_UTF_8);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;}}
}

2. PBKDF2 加密算法详解

2.1 技术原理

• PBKDF2（Password-Based Key Derivation Function 2）是一种基于密码的密钥派生函数，通过对密码加盐后进行多次哈希迭代，生成加密密钥或哈希值。
• 主要输入参数：密码、盐、迭代次数、哈希函数（如 HMAC-SHA256）、输出密钥长度。
• 公式示例：DK = PBKDF2(P, S, c, dkLen)，其中 DK 为派生密钥，P 为密码，S 为盐，c 为迭代次数，dkLen 为输出长度。

2.2 优缺点

优点：

• 安全性高：通过盐和多次迭代，有效抵抗字典和暴力破解。
• 参数可调：可自定义迭代次数和密钥长度，灵活性强。
• 标准广泛支持：被 PKCS#5、RFC 等标准收录，几乎所有主流加密库都支持。
  缺点：
• 计算资源消耗大：高迭代次数导致 CPU 负担重，不适合高性能或低功耗场景。
• 抗硬件攻击不如 Scrypt：仅依赖 CPU 迭代，内存占用可控，对 GPU/ASIC 攻击防御不如 Scrypt。

2.3 适用场景

• 密码存储：如数据库密码哈希，尤其适用于合规性要求高的系统。
• 密钥派生：为对称加密（如 AES）生成安全密钥。
• 加密文件/磁盘：如全盘加密、文件加密工具的密钥生成。

代码实现

实现了一个PBKDF2密码加密工具类。主要功能包括：
使用指定算法、密钥长度和迭代次数生成PBKDF2加密器
encrypt方法：对密码和盐值进行PBKDF2加密，返回字节数组
encryptHex方法：对密码和盐值进行PBKDF2加密，返回十六进制字符串格式的结果
支持自定义算法类型、密钥长度和迭代次数参数。

import cn.hutool.core.util.HexUtil;
import cn.hutool.crypto.KeyUtil;
import javax.crypto.SecretKey;
import javax.crypto.spec.PBEKeySpec;public class PBKDF2 {private String algorithm = "PBKDF2WithHmacSHA1";private int keyLength = 512;private int iterationCount = 1000;public PBKDF2() {}public PBKDF2(String algorithm, int keyLength, int iterationCount) {this.algorithm = algorithm;this.keyLength = keyLength;this.iterationCount = iterationCount;}public byte[] encrypt(char[] password, byte[] salt) {PBEKeySpec pbeKeySpec = new PBEKeySpec(password, salt, this.iterationCount, this.keyLength);SecretKey secretKey = KeyUtil.generateKey(this.algorithm, pbeKeySpec);return secretKey.getEncoded();}public String encryptHex(char[] password, byte[] salt) {return HexUtil.encodeHexStr(this.encrypt(password, salt));}
}import java.security.spec.KeySpec;
import java.util.Arrays;/**
用于指定基于密码加密（PBE）的密钥生成参数。它包含密码、盐值、迭代次数和密钥长度等属性，并提供了多个构造函数和 getter 方法来访问这些参数。还提供了 clearPassword 方法用于清空密码以增强安全性。
**/
public class PBEKeySpec implements KeySpec {private char[] password;private byte[] salt = null;private int iterationCount = 0;private int keyLength = 0;public PBEKeySpec(char[] password) {if (password != null && password.length != 0) {this.password = (char[])(([C)password).clone();} else {this.password = new char[0];}}public PBEKeySpec(char[] password, byte[] salt, int iterationCount, int keyLength) {if (password != null && password.length != 0) {this.password = (char[])(([C)password).clone();} else {this.password = new char[0];}if (salt == null) {throw new NullPointerException("the salt parameter must be non-null");} else if (salt.length == 0) {throw new IllegalArgumentException("the salt parameter must not be empty");} else {this.salt = (byte[])(([B)salt).clone();if (iterationCount <= 0) {throw new IllegalArgumentException("invalid iterationCount value");} else if (keyLength <= 0) {throw new IllegalArgumentException("invalid keyLength value");} else {this.iterationCount = iterationCount;this.keyLength = keyLength;}}}public PBEKeySpec(char[] password, byte[] salt, int iterationCount) {if (password != null && password.length != 0) {this.password = (char[])(([C)password).clone();} else {this.password = new char[0];}if (salt == null) {throw new NullPointerException("the salt parameter must be non-null");} else if (salt.length == 0) {throw new IllegalArgumentException("the salt parameter must not be empty");} else {this.salt = (byte[])(([B)salt).clone();if (iterationCount <= 0) {throw new IllegalArgumentException("invalid iterationCount value");} else {this.iterationCount = iterationCount;}}}public final void clearPassword() {if (this.password != null) {Arrays.fill(this.password, ' ');this.password = null;}}public final char[] getPassword() {if (this.password == null) {throw new IllegalStateException("password has been cleared");} else {return (char[])this.password.clone();}}public final byte[] getSalt() {return this.salt != null ? (byte[])this.salt.clone() : null;}public final int getIterationCount() {return this.iterationCount;}public final int getKeyLength() {return this.keyLength;}
}

3. BCrypt 与 PBKDF2 对比

特性	BCrypt	PBKDF2
算法类型	密码哈希（基于 Blowfish）	密钥派生函数（基于 HMAC）
加盐机制	自动生成并嵌入哈希结果	需显式指定盐，通常需单独存储
迭代次数/工作因子	可调 cost factor（指数级）	可调迭代次数（线性）
抗硬件攻击能力	中等（内存消耗固定）	较弱（主要依赖 CPU 迭代）
计算资源消耗	高（随 cost 增长）	高（随迭代次数增长）
适用场景	Web 密码存储、用户认证	密码存储、密钥派生、文件加密
主流支持	Spring Security、Node.js bcrypt	Java、Python、.NET 等所有主流库

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4. 总结与建议

• BCrypt 适合 Web 应用密码存储，尤其需要自动加盐和可调工作因子的场景，如 Spring Security 默认方案。
• PBKDF2 适合需要高合规性、密钥派生、跨平台支持的场景，如企业级密码存储、加密文件系统等。
• 若需更高抗硬件攻击能力，可考虑 Scrypt 或 Argon2 等新型算法。