24、数据加密-DES
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1、密码的安全性不依赖算法的保密性,而依赖于密钥。加密算法分类:对称加密算法,加密和解密使用同一个密钥;非对称加密算法,加密使用公钥,解密使用私钥。
ECB:电子码本,把数据分组,每组都各自生成码文,然后组合。
CBC:密码分组连接,加密时把前一个输出密文与当前明文异或再加密;解密时前一个解好的明文异或当前密文,再解密。
2、DES(Data Encryption Standard):最流行对称加密算法。明文64bit为一组进行加密。加密过程根据64bit初始密钥生成的16个48位子密钥K1-K16进行。
一、生成子密钥
(1)初始密钥K0,根据密钥转换表64bit->56bit。第一个57表示原数据第57位为现在的第一位。
(2)把56bit分成2组,每组左移下图位数(最终要形成K1-K16),合并后置换56bit->48bit,形成子密钥K1-K16
二、加密,解密对称K16-K1,其它顺序不变
(1)一组数据根据置换表初始置换,64bit->64bit
(2)数据分成两组Li、Ri,Ri根据查表32bit扩展到48bit
(3)Ri异或Ki得到Rin
(4)Rin的48bit分成8组,每组6bit,这n组对应第n个盒Sn(8组8个盒),把6bit转换成4bit。如:第3组为101011,取第1位和最后一位对应S3中第4行,中间四位对应S3第6列,找到一个数字(4bit)。此时R又变为32bit
(5)P盒查表置换,32bit->32bit
(6)循环从(2)开始,Li = Ri-1,Ri = Li-1 异或 Rin
(7)循环16次后合并,最后在置换一次得到加密后的密文。
3、各种表
//初始秘钥64bit到56bit转换表static const int DesTransform[56] = { 57, 49, 41, 33, 25, 17, 9, 1, 58, 50, 42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44, 36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6, 61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4}; //产生K1-K16的旋转表static const int SesRotations[16] ={ 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };//K1-K16 56bit到48bit转换表static const int DesPermuted[48] ={ 14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56,34, 53, 46, 42, 50, 36, 29, 32 };//原文数据组64bit初始转换表static const int DesInitial[64] ={ 58, 50, 42, 34, 26, 18, 10, 2, 60, 52, 44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48, 40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35, 27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31, 23, 15, 7};//Ri 32bit到48bit扩展表static const int DesExpansion[48] = { 32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1 };//8个4行16列盒子S,48bit到32bitstatic const int DesSbox[8][4][16] = { { {14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7}, {0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8}, {4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0}, {15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13} }, { {15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10}, {3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5}, {0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15}, {13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9} }, { {10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8}, {13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1}, {13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7}, {1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12} }, { {7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15}, {13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9}, {10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4}, {3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14} }, { {2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9}, {14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6}, {4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14}, {11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3} }, { {12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11}, {10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8}, {9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6}, {4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13} }, { {4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1}, {13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6}, {1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2}, {6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12} }, { {13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7}, {1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2}, {7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8}, {2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11} } };//P盒子,32bit到32bitstatic const int DesPbox[32] = { 16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6, 22, 11, 4, 25};//最后转换表64bit到64bitstatic const int DesFinal[64] ={ 40, 8, 48, 16, 56, 24, 64, 32, 39, 7, 47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62, 30, 37, 5, 45, 13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11, 51, 19, 59, 27, 34, 2, 42, 10, 50, 18, 58, 26, 33, 1, 41, 9, 49, 17, 57, 25};
4、根据表进行转换
//bits为源数据;mapping为转换表; n为源数据bit数 static void permute(unsigned char *bits, const int *mapping, int n){ unsigned char temp[8]; int i; //ceil取 >= 指定表达式的整数 memset(temp, 0, (int)ceil(n / 8)); for(i = 0; i < n; i++) bit_set(temp, i, bit_get(bits, mapping[i] - 1)); memcpy(bits, temp, (int)ceil(n / 8)); return;}
5、编码、解码处理函数
//key为密钥, direction选择解码还是译码 static int des_main(const unsigned char *source, unsigned char *target, const unsigned char *key, DesEorD direction){ //K1-K16, 56bit还需要转换到48bit static unsigned char subkeys[16][7]; unsigned char temp[8]; //K0分成左右32bit unsigned char lkey[4], rkey[4]; unsigned char lblk[6], rblk[6]; unsigned char fblk[6], xblk[6], sblk; int row, col, i, j, k, p; //生成子密钥 if(key != NULL) { memcpy(temp, key, 8); //K0 64bit->56bit permute(temp, DesTransform, 56); //分成左右28bit memset(lkey, 0, 4); memset(rkey, 0, 4); for(j = 0; j < 28; j++) bit_set(lkey, j, bit_get(temp, j)); for(j = 0; j < 28; j++) bit_set(rkey, j, bit_get(temp, j + 28)); //得到K1-K16 旋转,56bit->48bit for(i = 0; i < 16; i++) { bit_rot_left(lkey, 28, DesRotations[i]); bit_rot_left(rkey, 28, DesRotations[i]); for(j = 0; j < 28; j++) bit_set(subkeys[i], j, bit_get(lkey, j)); for(j = 0; j < 28; j++) bit_set(subkeys[i], j + 28, bit_get(lkey, j)); permute(subkeys[i], DesPermuted, 48); } } //取64bit数据 memcpy(temp, source, 8); //数据初始转换 permute(temp, DesInitial, 64); //分左右 memcpy(lblk, &temp[0], 4); memcpy(rblk, &temp[4], 4); for(i = 0; i < 16; i++) { //右32bit扩展到48bit memcpy(fblk, rblk, 4); permute(fblk, DesExpansion, 48); //编码处理过程是K1-K16,解码处理过程是K16-K1 if(direction == encipher) { bit_xor(fblk, subkeys[i], xblk, 48); memset(fblk, xblk, 6); } else { bit_xor(fblk, subkeys[16 - i], xblk, 48); memset(fblk, xblk, 6); } p = 0; //8组6bit处理 for(j = 0; j < 8; j++) { //找到每6bit对应的盒子Sj中的数字 row = (bit_get(fblk, (j * 6) + 0) * 2) + (bit_get(fblk, (j * 6) + 5) * 1); col = (bit_get(fblk, (j * 6) + 1) * 8) + (bit_get(fblk, (j * 6) + 2) * 4) + bit_get(fblk, (j * 6) + 3) * 2) + bit_get(fblk, (j * 6) + 4) * 1); sblk = (unsigned char)DesSbox[j][row][col]; for(k = 4; k < 8; k++) { bit_set(fblk, p, bit_get(&sblk, k)); p++; } } //P盒子转换 permute(fblk, DesPermuted, 32); bit_xor(lblk, fblk, xblk, 32); memset(lblk, rblk, 4); memset(rblk, xblk, 4); } //最后合并转换 memset(&target[0], rblk, 4); memset(&target[4], lblk, 4); permute(target, DesFinal, 64); return 0;}
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