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前几天刚写完一个简单的DES算法的实验，拿来作为第一次发到博客的随笔，填充一下空空如也的博客，献丑了
因为主要目的是Easy-To-Understand，再现一个直观的DES加解密的过程，所以很浪费地每一个数据位都用一个short整型存储，用来理ying解fu过zuo程ye就好（虽说DES这种对称加密算法十多年前就已经被淘汰了，现在一般建议用AES或者DES3
“1973 年，美国国家标准局（NBS）开始征集一种标准的数据加密标准算法（DES），以用于非机密性政府机构、商业部门和民间的对非机密的敏感数据进行加密。IBM 公司在1971年完成的LUCIFER 密码（64 比特分组，128 比特密钥)的基础上，改进成为建议的DES。改进后的DES算法仅使用56比特密钥，同时对S盒的修改被列入官方机密，曾广受批评。1975 年3 月17 日，NBS 公布了这个算法，并说明要以它作为联邦信息处理标准，征求各方意见。1977 年1 月15 日，建议被批准为联邦标准—FIPSPUB 46，并设计推出了DES 芯片。1981 年，ANSI 将DES 作为标准，即DEA[ANSI X3.92]。1983 年，ISO 采用DES 作为标准，即DEA-1。DES（Data Encryption Standard）是一个优秀的对称分组密码算法，直到2000 年10 月2 日NIST 宣布AES 算法前，其一直是业界的标准。”
1 #pragma once 2 3 void des_setup(const short* key); 4 void des_encrypt(const short *pt, short *ct); 5 void des_decrypt(const short *pt, short *ct);
1 short sKey[16][48]; 2 3 short sBox_1[4][16] = { 4 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7, 5 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8, 6 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0, 7 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 8 }; 9 10 short sBox_2[4][16] = { 11 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10, 12 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5, 13 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15, 14 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 15 }; 16 17 short sBox_3[4][16] = { 18 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8, 19 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1, 20 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7, 21 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 22 }; 23 24 short sBox_4[4][16] = { 25 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15, 26 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9, 27 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4, 28 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 29 }; 30 31 short sBox_5[4][16] = { 32 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9, 33 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6, 34 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14, 35 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 36 }; 37 38 short sBox_6[4][16] = { 39 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11, 40 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8, 41 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6, 42 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 43 }; 44 45 short sBox_7[4][16] = { 46 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1, 47 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6, 48 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2, 49 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 50 }; 51 52 short sBox_8[4][16] = { 53 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7, 54 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2, 55 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8, 56 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 57 }; 58 59 short KuoChongZhiHuan_E[48] = { 60 32, 1, 2, 3, 4, 5, 61 4, 5, 6, 7, 8, 9, 62 8, 9, 10, 11, 12, 13, 63 12, 13, 14, 15, 16, 17, 64 16, 17, 18, 19, 20, 21, 65 20, 21, 22, 23, 24, 25, 66 24, 25, 26, 27, 28, 29, 67 28, 29, 30, 31, 32, 1 68 }; 69 70 short ZhiHuanHanShu_P[32] = { 71 16, 7, 20, 21, 29, 12, 28, 17, 72 1, 15, 23, 26, 5, 18, 31, 10, 73 2, 8, 24, 14, 32, 27, 3, 9, 74 19, 13, 30, 6, 22, 11, 4, 25 75 }; 76 77 short ZhiHuanXuanZe_1[56] = { 78 57, 49, 41, 33, 25, 17, 9, 79 1, 58, 50, 42, 34, 26, 18, 80 10, 2, 59, 51, 43, 35, 27, 81 19, 11, 3, 60, 52, 44, 36, 82 63, 55, 47, 39, 31, 23, 15, 83 7, 62, 54, 46, 38, 30, 22, 84 14, 6, 61, 53, 45, 37, 29, 85 21, 13, 5, 28, 20, 12, 4 86 }; 87 88 short XunHuanZuoYi[16] = { 89 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 90 }; 91 92 short ZhiHuanXuanZe_2[48] = { 93 14, 17, 11, 24, 1, 5, 3, 28, 94 15, 6, 21, 10, 23, 19, 12, 4, 95 26, 8, 16, 7, 27, 20, 13, 2, 96 41, 52, 31, 37, 47, 55, 30, 40, 97 51, 45, 33, 48, 44, 49, 39, 56, 98 34, 53, 46, 42, 50, 36, 29, 32 99 }; 100 101 short ChuShiZhiHuan[64] = { 102 58, 50, 42, 34, 26, 18, 10, 2, 103 60, 52, 44, 36, 28, 20, 12, 4, 104 62, 54, 46, 38, 30, 22, 14, 6, 105 64, 56, 48, 40, 32, 24, 16, 8, 106 57, 49, 41, 33, 25, 17, 9, 1, 107 59, 51, 43, 35, 27, 19, 11, 3, 108 61, 53, 45, 37, 29, 21, 13, 5, 109 63, 55, 47, 39, 31, 23, 15, 7 110 }; 111 112 short NiChuShiZhiHuan[64] = { 113 40, 8, 48, 16, 56, 24, 64, 32, 114 39, 7, 47, 15, 55, 23, 63, 31, 115 38, 6, 46, 14, 54, 22, 62, 30, 116 37, 5, 45, 13, 53, 21, 61, 29, 117 36, 4, 44, 12, 52, 20, 60, 28, 118 35, 3, 43, 11, 51, 19, 59, 27, 119 34, 2, 42, 10, 50, 18, 58, 26, 120 33, 1, 41, 9, 49, 17, 57, 25 121 }; 122 123 void des_setup(const short* key) 124 { 125 short tempKey[56]; 126 for (int i = 0; i < 56; ++i) { 127 tempKey[i] = key[ZhiHuanXuanZe_1[i] - 1]; 128 } 129 for (int i = 0; i < 16; ++i) { 130 for (int j = 0; j < XunHuanZuoYi[i]; ++j) { 131 short temp = tempKey[0]; 132 for (int m = 0; m < 27; ++m) { 133 tempKey[m] = tempKey[m + 1]; 134 } 135 tempKey[27] = temp; 136 temp = tempKey[28]; 137 for (int m = 28; m < 55; ++m) { 138 tempKey[m] = tempKey[m + 1]; 139 } 140 tempKey[55] = temp; 141 } 142 for (int j = 0; j < 48; ++j) { 143 sKey[i][j] = tempKey[ZhiHuanXuanZe_2[j] - 1]; 144 } 145 } 146 } 147 148 void desfun(short *BlockL, short *BlockR, int round) 149 { 150 short tempBlock_48[48]; 151 //扩充E 152 for (int i = 0; i < 48; ++i) { 153 tempBlock_48[i] = *(BlockR + KuoChongZhiHuan_E[i] - 1); 154 } 155 //异或 156 for (int i = 0; i < 48; ++i) { 157 if (tempBlock_48[i] == sKey[round][i]) 158 tempBlock_48[i] = 0; 159 else 160 tempBlock_48[i] = 1; 161 } 162 //S盒代换 163 short tempBlock_32[32]; 164 for (int i = 0, j = 0; i < 48; i += 6, j += 4) { 165 switch (sBox_1[2 * tempBlock_48[i] + tempBlock_48[5]][8 * tempBlock_48[i + 1] + 4 * tempBlock_48[i + 2] + 2 * tempBlock_48[i + 3] + tempBlock_48[i + 4]]) { 166 case 0: 167 tempBlock_32[j] = 0; 168 tempBlock_32[j + 1] = 0; 169 tempBlock_32[j + 2] = 0; 170 tempBlock_32[j + 3] = 0; 171 break; 172 case 1: 173 tempBlock_32[j] = 0; 174 tempBlock_32[j + 1] = 0; 175 tempBlock_32[j + 2] = 0; 176 tempBlock_32[j + 3] = 1; 177 break; 178 case 2: 179 tempBlock_32[j] = 0; 180 tempBlock_32[j + 1] = 0; 181 tempBlock_32[j + 2] = 1; 182 tempBlock_32[j + 3] = 0; 183 break; 184 case 3: 185 tempBlock_32[j] = 0; 186 tempBlock_32[j + 1] = 0; 187 tempBlock_32[j + 2] = 1; 188 tempBlock_32[j + 3] = 1; 189 break; 190 case 4: 191 tempBlock_32[j] = 0; 192 tempBlock_32[j + 1] = 1; 193 tempBlock_32[j + 2] = 0; 194 tempBlock_32[j + 3] = 0; 195 break; 196 case 5: 197 tempBlock_32[j] = 0; 198 tempBlock_32[j + 1] = 1; 199 tempBlock_32[j + 2] = 0; 200 tempBlock_32[j + 3] = 1; 201 break; 202 case 6: 203 tempBlock_32[j] = 0; 204 tempBlock_32[j + 1] = 1; 205 tempBlock_32[j + 2] = 1; 206 tempBlock_32[j + 3] = 0; 207 break; 208 case 7: 209 tempBlock_32[j] = 0; 210 tempBlock_32[j + 1] = 1; 211 tempBlock_32[j + 2] = 1; 212 tempBlock_32[j + 3] = 1; 213 break; 214 case 8: 215 tempBlock_32[j] = 1; 216 tempBlock_32[j + 1] = 0; 217 tempBlock_32[j + 2] = 0; 218 tempBlock_32[j + 3] = 0; 219 break; 220 case 9: 221 tempBlock_32[j] = 1; 222 tempBlock_32[j + 1] = 0; 223 tempBlock_32[j + 2] = 0; 224 tempBlock_32[j + 3] = 1; 225 break; 226 case 10: 227 tempBlock_32[j] = 1; 228 tempBlock_32[j + 1] = 0; 229 tempBlock_32[j + 2] = 1; 230 tempBlock_32[j + 3] = 0; 231 break; 232 case 11: 233 tempBlock_32[j] = 1; 234 tempBlock_32[j + 1] = 0; 235 tempBlock_32[j + 2] = 1; 236 tempBlock_32[j + 3] = 1; 237 break; 238 case 12: 239 tempBlock_32[j] = 1; 240 tempBlock_32[j + 1] = 1; 241 tempBlock_32[j + 2] = 0; 242 tempBlock_32[j + 3] = 0; 243 break; 244 case 13: 245 tempBlock_32[j] = 1; 246 tempBlock_32[j + 1] = 1; 247 tempBlock_32[j + 2] = 0; 248 tempBlock_32[j + 3] = 1; 249 break; 250 case 14: 251 tempBlock_32[j] = 1; 252 tempBlock_32[j + 1] = 1; 253 tempBlock_32[j + 2] = 1; 254 tempBlock_32[j + 3] = 0; 255 break; 256 case 15: 257 tempBlock_32[j] = 1; 258 tempBlock_32[j + 1] = 1; 259 tempBlock_32[j + 2] = 1; 260 tempBlock_32[j + 3] = 1; 261 break; 262 } 263 } 264 //置换P 265 short afterP[32]; 266 for (int i = 0; i < 32; ++i) { 267 afterP[i] = tempBlock_32[ZhiHuanHanShu_P[i] - 1]; 268 } 269 //备份Ri-1 270 short oldBlockR[32]; 271 for (int i = 0; i < 32; ++i) { 272 oldBlockR[i] = BlockR[i]; 273 } 274 //异或=>Ri 275 for (int i = 0; i < 32; ++i) { 276 if (afterP[i] == *(BlockL + i)) 277 BlockR[i] = 0; 278 else 279 BlockR[i] = 1; 280 } 281 //Ri-1=>Li 282 for (int i = 0; i < 32; ++i) { 283 BlockL[i] = oldBlockR[i]; 284 } 285 } 286 287 void des_encrypt(const short *pt, short *ct) 288 { 289 short Block[64]; 290 short BlockL[32]; 291 short BlockR[32]; 292 //初始置换 293 for (int i = 0; i < 64; ++i) { 294 Block[i] = pt[ChuShiZhiHuan[i] - 1]; 295 } 296 //分成左右两块 297 for (int i = 0; i < 32; ++i) { 298 BlockL[i] = Block[i]; 299 BlockR[i] = Block[i + 32]; 300 } 301 //16轮desfun 302 for (int i = 0; i < 16; ++i) { 303 desfun(BlockL, BlockR, i); 304 } 305 //32位互换 306 for (int i = 0; i < 32; ++i) { 307 short temp = BlockL[i]; 308 BlockL[i] = BlockR[i]; 309 BlockR[i] = temp; 310 } 311 for (int i = 0; i < 32; ++i) { 312 Block[i] = BlockL[i]; 313 Block[i + 32] = BlockR[i]; 314 } 315 //逆初始置换 316 for (int i = 0; i < 64; ++i) { 317 ct[i] = Block[NiChuShiZhiHuan[i] - 1]; 318 } 319 } 320 321 void des_decrypt(const short *pt, short *ct) 322 { 323 short Block[64]; 324 short BlockL[32]; 325 short BlockR[32]; 326 //初始置换 327 for (int i = 0; i < 64; ++i) { 328 Block[i] = pt[ChuShiZhiHuan[i] - 1]; 329 } 330 //分成左右两块 331 for (int i = 0; i < 32; ++i) { 332 BlockL[i] = Block[i]; 333 BlockR[i] = Block[i + 32]; 334 } 335 //16轮desfun（与加密唯一的不同处） 336 for (int i = 15; i >= 0; --i) { 337 desfun(BlockL, BlockR, i); 338 } 339 //32位互换 340 for (int i = 0; i < 32; ++i) { 341 short temp = BlockL[i]; 342 BlockL[i] = BlockR[i]; 343 BlockR[i] = temp; 344 } 345 for (int i = 0; i < 32; ++i) { 346 Block[i] = BlockL[i]; 347 Block[i + 32] = BlockR[i]; 348 } 349 //逆初始置换 350 for (int i = 0; i < 64; ++i) { 351 ct[i] = Block[NiChuShiZhiHuan[i] - 1]; 352 } 353 }
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原文地址：http://www.cnblogs.com/shing0315/p/5399724.html
