RC4加密与解密 |
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RC4加密与解密
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介绍
在密码学中，RC4（Rivest Cipher 4，也称为ARC4或ARCFOUR，意为所谓的RC4）是一种流密码。尽管它以简单性和软件速度着称，但在RC4中发现了多个漏洞，使其不安全。当不丢弃输出密钥流的开头或使用非随机或相关密钥时，它特别容易受到攻击。RC4的使用特别有问题，导致协议非常不安全，例如WEP。 参数介绍 参数名 说明 S S-box，长度为256的char型数组，char S[256] K 密钥Key，用户自定义，长度在1~256，用来打乱S-box T 临时变量，长度为256的char型数组 D 保存加密前/后数据 基本流程 初始化 S 和 T 数组。 初始化置换 S。 生成密钥流。 初始化S和T数组+初始化置换S void RC4_Init(unsigned char* S, unsigned char* K, unsigned int len) { int i, j = 0; unsigned char ch_tmp, T[256] = { 0 };//临时变量 for (i = 0; i < 256; ++i) { S[i] = i;//初始化S-box T[i] = K[i % len];//密钥填充临时数组 } //打乱S-box for (i = 0; i < 256; ++i) { j = (j + S[i] + T[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; } } 生成密钥流 void RC4_Crypt(unsigned char* S, unsigned char* D, unsigned int len) { int i = 0, j = 0, int_tmp; unsigned int n; unsigned char ch_tmp; for (n = 0; n < len; ++n) { i = (i + 1) % 256; j = (j + S[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; int_tmp = (S[i] + S[j]) % 256; D[n] ^= S[n]; } } 完整代码实现 C语言 #include #pragma warning(disable:4996) void RC4_Init(unsigned char* S, unsigned char* K, unsigned int len) { int i, j = 0; unsigned char ch_tmp, T[256] = { 0 };//临时变量 for (i = 0; i < 256; ++i) { S[i] = i;//初始化S-box T[i] = K[len % 256];//密钥填充临时数组 } //打乱S-box for (i = 0; i < 256; ++i) { j = (j + S[i] + T[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; } } void RC4_Crypt(unsigned char* S, unsigned char* D, unsigned int len) { int i = 0, j = 0, int_tmp; unsigned int n; unsigned char ch_tmp; for (n = 0; n < len; ++n) { i = (i + 1) % 256; j = (j + S[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; int_tmp = (S[i] + S[j]) % 256; D[n] ^= S[n]; } } int main(void) { unsigned char S_box[256] = { 0 }; unsigned char Key[] = { "helloworld" }; unsigned char Data[] = { "youareso" }; int i; printf("加密前数据：%s\n\n", Data); printf("密钥：%s\n\n", Key); RC4_Init(S_box, Key, strlen((char*)Key)); printf("S-box：\n"); for (i = 0; i < 256; ++i) { printf("%02x", S_box[i]); if ((i + 1) % 16 == 0) printf("\n"); } RC4_Crypt(S_box, Data, strlen((char*)Data)); printf("\n加密后数据：%s\n", Data); system("PAUSE"); return 0; }
RC4+Base64 不过在实际做题中，往往会将RC4与变表Base64结合起来考（先后顺序） #include #pragma warning(disable:4996) void RC4_Init(unsigned char* S, unsigned char* K, unsigned int len) { int i, j = 0; unsigned char ch_tmp, T[256] = { 0 };//临时变量 for (i = 0; i < 256; ++i) { S[i] = i;//初始化S-box T[i] = K[len % 256];//密钥填充临时数组 } //打乱S-box for (i = 0; i < 256; ++i) { j = (j + S[i] + T[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; } } void RC4_Crypt(unsigned char* S, unsigned char* D, unsigned int len) { int i = 0, j = 0, int_tmp; unsigned int n; unsigned char ch_tmp; for (n = 0; n < len; ++n) { i = (i + 1) % 256; j = (j + S[i]) % 256; ch_tmp = S[i]; S[i] = S[j]; S[j] = ch_tmp; int_tmp = (S[i] + S[j]) % 256; D[n] ^= S[n]; } } unsigned char* base64_encode(unsigned char* str) { long len; long str_len; unsigned char* res = { 0 }; int i, j; unsigned char base64_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; //unsigned char base64_table[] = "0123456789+/abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; str_len = strlen((char*)str); if (str_len % 3 == 0) len = str_len / 3 * 4; else len = (str_len / 3 + 1) * 4; res = (unsigned char*)malloc(sizeof(unsigned char) * len + 1); res[len] = '\0'; for (i = 0, j = 0; i < len - 2; j += 3, i += 4) { res[i] = base64_table[str[j] >> 2]; res[i + 1] = base64_table[(str[j] & 0x3) > 4)]; res[i + 2] = base64_table[(str[j + 1] & 0xf) > 6)]; res[i + 3] = base64_table[str[j + 2] & 0x3f]; } switch (str_len % 3) { case 1: res[i - 2] = '='; res[i - 1] = '='; break; case 2: res[i - 1] = '='; break; } return res; } unsigned char* base64_decode(unsigned char* code) { //根据base64表，以字符找到对应的十进制数据 int table[] = { 0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,62,0,0,0, 63,52,53,54,55,56,57,58, 59,60,61,0,0,0,0,0,0,0,0, 1,2,3,4,5,6,7,8,9,10,11,12, 13,14,15,16,17,18,19,20,21, 22,23,24,25,0,0,0,0,0,0,26, 27,28,29,30,31,32,33,34,35, 36,37,38,39,40,41,42,43,44, 45,46,47,48,49,50,51 }; long len; long str_len; unsigned char* res; int i, j; //计算解码后的字符串长度 len = strlen((char*)code); //判断编码后的字符串后是否有= if (strstr((char*)code, "==")) str_len = len / 4 * 3 - 2; else if (strstr((char*)code, "=")) str_len = len / 4 * 3 - 1; else str_len = len / 4 * 3; res = (unsigned char*)malloc(sizeof(unsigned char) * str_len + 1); res[str_len] = '\0'; //以4个字符为一位进行解码 for (i = 0, j = 0; i < len - 2; j += 3, i += 4) { res[j] = ((unsigned char)table[code[i]]) > 4); //取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的后2位进行组合 res[j + 1] = (((unsigned char)table[code[i + 1]]) > 2); //取出第二个字符对应base64表的十进制数的后4位与第三个字符对应bas464表的十进制数的后4位进行组合 res[j + 2] = (((unsigned char)table[code[i + 2]]) |
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