因学习需要，在网上找SMS4的C实现，没有找到满意的。所以自己写了一个，现分享之，希望能帮到有需要的朋友。
实现的时候，用到了一些C99的新特性。
接下来，就是SMS4的C语言实现。没有做优化，以后有时间了，会再改进。
一：头文件 "sms4.h"
/* * ============================================================================ * * Filename: sms4.h * * Description: Public interface for the SMS4 encryption algorithm. * * Version: 1.0 * Created: 2012年04月01日 15时18分14秒 * Revision: none * Compiler: gcc * * Author: Long, longcpp9@gmail.com * Company: SDU * * ============================================================================ */ #ifndef SMS4_INCLUDED #define SMS4_INCLUDED void sms4_encrypt(void *plaintext, void const *key); void sms4_decrypt(void *ciphertext, void const *key); #endif /* SMS4_INCLUDED */
二：实现文件 "sms4.c"
/* * ============================================================================ * * Filename: sms4.c * * Description: Implementation of SMS4 * * Version: 1.0 * Created: 2012年04月01日 13时36分06秒 * Revision: none * Compiler: gcc * * Author: Long, longcpp9@gmail.com * Company: SDU * * ============================================================================ */ #include <stdlib.h> #include <stdint.h> #include <inttypes.h> #include <stdio.h> #include <string.h> #include "sms4.h" #define ROUND 32 static uint8_t sms4_sbox[256] = { 0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05, 0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99, 0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62, 0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6, 0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8, 0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35, 0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87, 0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e, 0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1, 0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3, 0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f, 0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51, 0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8, 0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0, 0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84, 0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48 }; static uint32_t sms4_ck[32] = { 0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269, 0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9, 0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249, 0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9, 0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229, 0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299, 0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209, 0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279 }; static inline uint32_t rotate_left(uint32_t x, uint8_t n) { return ((x << n) | (x >> (32 - n))); } static inline uint32_t L_trans(uint32_t x) { return (x ^ rotate_left(x, 2) ^ rotate_left(x, 10) ^ rotate_left(x, 18) ^ rotate_left(x, 24)); } static inline uint32_t key_L_trans(uint32_t x) { return (x ^ rotate_left(x, 13) ^ rotate_left(x, 23)); } static inline uint32_t s_substitute(uint32_t x) { uint8_t *px = (uint8_t *)&x; px[0] = sms4_sbox[px[0]]; px[1] = sms4_sbox[px[1]]; px[2] = sms4_sbox[px[2]]; px[3] = sms4_sbox[px[3]]; return x; } static inline uint32_t T_trans(uint32_t x) { return (L_trans(s_substitute(x))); } static inline uint32_t key_T_trans(uint32_t x) { return (key_L_trans(s_substitute(x))); } static inline void sms4_round_func(uint32_t *input, uint32_t sub_key) { uint32_t tmp = input[0]; input[0] = input[1]; input[1] = input[2]; input[2] = input[3]; input[3] = tmp ^ T_trans(input[0] ^ input[1] ^ input[2] ^ sub_key); } static inline void sms4_reverse(uint32_t *input) { uint32_t tmp; tmp = input[0], input[0] = input[3], input[3] = tmp; tmp = input[1], input[1] = input[2], input[2] = tmp; } static void sms4_key_schedule(uint32_t const *key, uint32_t *round_key) { int j; uint32_t buf[4]; uint32_t *prk = (uint32_t *)round_key; memcpy(buf, key, 16); buf[0] ^= 0xa3b1bac6; buf[1] ^= 0x56aa3350; buf[2] ^= 0x677d9197; buf[3] ^= 0xb27022dc; for(j = 0; j < ROUND; ++j){ prk[j] = buf[0] ^ key_T_trans(buf[1] ^ buf[2] ^ buf[3] ^ sms4_ck[j]); buf[0] = buf[1]; buf[1] = buf[2]; buf[2] = buf[3]; buf[3] = prk[j]; } } void sms4_encrypt(void *plaintext, void const *key) { uint32_t round_key[ROUND] = {0}; sms4_key_schedule(key, round_key); int i; for(i = 0; i < ROUND; ++i) sms4_round_func((uint32_t *)plaintext, round_key[i]); sms4_reverse((uint32_t *)plaintext); } void sms4_decrypt(void *ciphertext, void const *key) { uint32_t round_key[ROUND] = {0}; sms4_key_schedule(key, round_key); int i; for(i = 0; i < ROUND; ++i) sms4_round_func((uint32_t *)ciphertext, round_key[31-i]); sms4_reverse((uint32_t *)ciphertext); }
在实现SMS4时，本着一个原则来设计函数接口，即：
共用接口的函数，对参数类型的限制尽可能小（因为我们并不知道用户程序究竟会用怎样的数据类型来存储明文），故参数类型设置为void *，而那些用于实现共用接口的函数的参数类型，限制比较多，因为这些是我们可以控制的（我还不很确定这样的到底是否合适，暂且就这样吧）。
三：测试文件 "sms4_test.c"
/* * ============================================================================ * * Filename: sms4_test.c * * Description: Test the implementation of sms4. * * Version: 1.0 * Created: 2012年04月01日 15时20分44秒 * Revision: none * Compiler: gcc * * Author: Long, longcpp9@gmail.com * Company: SDU * * ============================================================================ */ #include <stdio.h> #include <stdlib.h> #include <inttypes.h> #include "sms4.h" void print(uint32_t *buf, int size) { int i = 0; for(i = 0; i < size; ++i) printf("%08" PRIx32 " ", buf[i]); printf("\n"); } int main(int argc, const char *argv[]) { uint32_t buffer[4] = {0x01234567, 0x89abcdef, 0xfedcba98, 0x76543210}; uint32_t key[4] = {0x01234567, 0x89abcdef, 0xfedcba98, 0x76543210}; printf("the plaintext:\t"); print(buffer, 4); printf("the key:\t"); print(key, 4); sms4_encrypt(buffer, key); printf("the ciphertext:\t"); print(buffer, 4); sms4_decrypt(buffer, key); printf("the plaintext:\t"); print(buffer, 4); exit(EXIT_SUCCESS); }
程序所输出的结果，与SMS4的官方文档中给出的示例一样，如下：（改成循环加密1000000次，所得结果与官方文档中也一样，大家可以测试）
1 the plaintext: 01234567 89abcdef fedcba98 76543210 2 the key: 01234567 89abcdef fedcba98 76543210 3 the ciphertext: 681edf34 d206965e 86b3e94f 536e4246 4 the plaintext: 43267f05 e9acb3f8 bf0e4dbd 43604a8b
大概就是这样了，有不合适的地方，请批评指正。