SM4是我们自己国家的一个分组密码算法，是国家密码管理局于2012年发布的。网址戳→_→：http://www.cnnic.NET.cn/jscx/mixbz/sm4/
具体的密码标准和算法官方有非常详尽的PDF文档以供查阅，戳→_→：http://218.241.108.63/wiki/images/2/22/SM4%E5%88%86%E7%BB%84%E5%AF%86%E7%A0%81%E7%AE%97%E6%B3%95.pdf
算法的源码实现官方也有相应的示例源码，戳→_→：
http://218.241.108.63/wiki/index.PHP/File:Sm2_sm3_sm4_c%E8%AF%AD%E8%A8%80%E5%AE%9E%E7%8E%B0.zip
先说说啥是分组密码算法：
分组密码算法——国际DES、国产SM4
分组密码就是将明文数据按固定长度进行分组，然后在同一密钥控制下逐组进行加密，从而将各个明文分组变换成一个等长的密文分组的密码。其中二进制明文分组的长度称为该分组密码的分组规模。
SM4密码算法的整体结构图如下：
在SM4的源代码中存在如下几个函数:
void sm4_setkey_enc(sm4_context *ctx，unsigned char key[16])
void sm4_setkey_dec(sm4_context *ctx，unsigned char key[16])
void sm4_crypt_ecb( sm4_context *ctx,int mode,int length, unsigned char *input,unsigned char *output)
void sm4_crypt_cbc( sm4_context *ctx,int mode,int length,unsigned char iv[16],unsigned char *input,unsigned char *output )
static void sm4_setkey( unsigned long SK[32], unsigned char key[16] )
还有一个非常重要的结构体：sm4_context
typedef struct
{
int mode; /*!< encrypt/decrypt */
unsigned long sk[32]; /*!< SM4 subkeys */
}
sm4_context;
先说结构体：
sm4_context结构体中的Mode控制是加密还是解密，sk则表示子密钥，也称作轮密钥。
第一个函数： void sm4_setkey_enc(sm4_context *ctx，unsigned char key[16])
这个函数是用来设置加密密钥的，一个参数分别为sm4_context *ctx和一个key。
其内部会调用static void sm4_setkey( unsigned long SK[32], unsigned char key[16] )函数
这个函数是用来设置密钥的，这个函数内部会对当前传入的主密钥进行32轮的迭代，每次迭代的轮密钥都被存放到ctx结构中的sk数组中。
void sm4_setkey_dec(sm4_context *ctx，unsigned char key[16])函数就是解密函数，过程为上述过程的逆序过程。
第二个函数：void sm4_crypt_ecb( sm4_context *ctx,int mode,int length, unsigned char
这个函数的作用是使用ecb模式（ECB（Electronic Codebook，电码本）模式是分组密码的一种最基本的工作模式。同样，sm4_crypt_cbc函数则是使用的CBC模式，也就是分组链接模式）来对内容进行加密，内部也是一个循环，根据length的长度来进行循环，每次循环都调用sm4_one_round进行加密或者解密，到底是加密还是解密，主要是根据第二个参数Mode来进行决定。
以上就是整个SM4算法的函数简介，运用这些函数接口，我们不需要知道内部的具体实现，就可以使用sm4加密算法来对我们的数据进行加解密，十分的方便。
/*测试代码 * SM4/SMS4 algorithm test programme * 2012-4-21 */#include <string.h>#include <stdio.h>#include "sm4.h"int main(){unsigned char key[16] = {0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef,0xfe,0xdc,0xba,0x98,0x76,0x54,0x32,0x10};unsigned char input[16] = {0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef,0xfe,0xdc,0xba,0x98,0x76,0x54,0x32,0x10};unsigned char output[16];sm4_context ctx;unsigned long i;//encrypt standard testing vectorsm4_setkey_enc(&ctx,key);sm4_crypt_ecb(&ctx,1,16,input,output);for(i=0;i<16;i++)printf("%02x ", output[i]);printf("\n");//decrypt testingsm4_setkey_dec(&ctx,key);sm4_crypt_ecb(&ctx,0,16,output,output);for(i=0;i<16;i++)printf("%02x ", output[i]);printf("\n"); return 0;}
/** * \file sm4.h */#ifndef XYSSL_SM4_H#define XYSSL_SM4_H#define SM4_ENCRYPT 1#define SM4_DECRYPT 0/** * \brief SM4 context structure */typedef struct{ int mode; /*!< encrypt/decrypt */ unsigned long sk[32]; /*!< SM4 subkeys */}sm4_context;#ifdef __cplusplusextern "C" {#endif/** * \brief SM4 key schedule (128-bit, encryption) * * \param ctx SM4 context to be initialized * \param key 16-byte secret key */void sm4_setkey_enc( sm4_context *ctx, unsigned char key[16] );/** * \brief SM4 key schedule (128-bit, decryption) * * \param ctx SM4 context to be initialized * \param key 16-byte secret key */void sm4_setkey_dec( sm4_context *ctx, unsigned char key[16] );/** * \brief SM4-ECB block encryption/decryption * \param ctx SM4 context * \param mode SM4_ENCRYPT or SM4_DECRYPT * \param length length of the input data * \param input input block * \param output output block */void sm4_crypt_ecb( sm4_context *ctx, int mode, int length, unsigned char *input, unsigned char *output);#ifdef __cplusplus}#endif#endif /* sm4.h */
/* * SM4 Encryption alogrithm (SMS4 algorithm) * GM/T 0002-2012 Chinese National Standard ref:http://www.oscca.gov.cn/ * thanks to Xyssl * thnaks and refers to http://hi.baidu.com/numax/blog/item/80addfefddfb93e4cf1b3e61.html * author:goldboar * email:goldboar@163.com * 2012-4-20 */// Test vector 1// plain: 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 10// key: 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 10// round key and temp computing result:// rk[ 0] = f12186f9 X[ 0] = 27fad345// rk[ 1] = 41662b61 X[ 1] = a18b4cb2// rk[ 2] = 5a6ab19a X[ 2] = 11c1e22a// rk[ 3] = 7ba92077 X[ 3] = cc13e2ee// rk[ 4] = 367360f4 X[ 4] = f87c5bd5// rk[ 5] = 776a0c61 X[ 5] = 33220757// rk[ 6] = b6bb89b3 X[ 6] = 77f4c297// rk[ 7] = 24763151 X[ 7] = 7a96f2eb// rk[ 8] = a520307c X[ 8] = 27dac07f// rk[ 9] = b7584dbd X[ 9] = 42dd0f19// rk[10] = c30753ed X[10] = b8a5da02// rk[11] = 7ee55b57 X[11] = 907127fa// rk[12] = 6988608c X[12] = 8b952b83// rk[13] = 30d895b7 X[13] = d42b7c59// rk[14] = 44ba14af X[14] = 2ffc5831// rk[15] = 104495a1 X[15] = f69e6888// rk[16] = d120b428 X[16] = af2432c4// rk[17] = 73b55fa3 X[17] = ed1ec85e// rk[18] = cc874966 X[18] = 55a3ba22// rk[19] = 92244439 X[19] = 124b18aa// rk[20] = e89e641f X[20] = 6ae7725f// rk[21] = 98ca015a X[21] = f4cba1f9// rk[22] = c7159060 X[22] = 1dcdfa10// rk[23] = 99e1fd2e X[23] = 2ff60603// rk[24] = b79bd80c X[24] = eff24fdc// rk[25] = 1d2115b0 X[25] = 6fe46b75// rk[26] = 0e228aeb X[26] = 893450ad// rk[27] = f1780c81 X[27] = 7b938f4c// rk[28] = 428d3654 X[28] = 536e4246// rk[29] = 62293496 X[29] = 86b3e94f// rk[30] = 01cf72e5 X[30] = d206965e// rk[31] = 9124a012 X[31] = 681edf34// cypher: 68 1e df 34 d2 06 96 5e 86 b3 e9 4f 53 6e 42 46//// test vector 2// the same key and plain 1000000 times coumpting // plain: 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 10// key: 01 23 45 67 89 ab cd ef fe dc ba 98 76 54 32 10// cypher: 59 52 98 c7 c6 fd 27 1f 04 02 f8 04 c3 3d 3f 66#include "sm4.h"#include <string.h>#include <stdio.h>/* * 32-bit integer manipulation macros (big endian) */#ifndef GET_ULONG_BE#define GET_ULONG_BE(n,b,i) \{ \ (n) = ( (unsigned long) (b)[(i) ] << 24 ) \ | ( (unsigned long) (b)[(i) + 1] << 16 ) \ | ( (unsigned long) (b)[(i) + 2] << 8 ) \ | ( (unsigned long) (b)[(i) + 3] ); \}#endif#ifndef PUT_ULONG_BE#define PUT_ULONG_BE(n,b,i) \{ \ (b)[(i) ] = (unsigned char) ( (n) >> 24 ); \ (b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \ (b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \ (b)[(i) + 3] = (unsigned char) ( (n) ); \}#endif/* *rotate shift left marco definition * */#define SHL(x,n) (((x) & 0xFFFFFFFF) << n)#define ROTL(x,n) (SHL((x),n) | ((x) >> (32 - n)))#define SWAP(a,b) { unsigned long t = a; a = b; b = t; t = 0; }/* * Expanded SM4 S-boxes /* Sbox table: 8bits input convert to 8 bits output*/ static const unsigned char SboxTable[16][16] = {{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}};/* System parameter */static const unsigned long FK[4] = {0xa3b1bac6,0x56aa3350,0x677d9197,0xb27022dc};/* fixed parameter */static const unsigned long 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};/* * private function: * look up in SboxTable and get the related value. * args: [in] inch: 0x00~0xFF (8 bits unsigned value). */static unsigned char sm4Sbox(unsigned char inch){ unsigned char *pTable = (unsigned char *)SboxTable; unsigned char retVal = (unsigned char)(pTable[inch]); return retVal;}/* * private F(Lt) function: * "T algorithm" == "L algorithm" + "t algorithm". * args: [in] a: a is a 32 bits unsigned value; * return: c: c is calculated with line algorithm "L" and nonline algorithm "t" */static unsigned long sm4Lt(unsigned long ka){ unsigned long bb = 0; unsigned long c = 0; unsigned char a[4];unsigned char b[4]; PUT_ULONG_BE(ka,a,0) b[0] = sm4Sbox(a[0]); b[1] = sm4Sbox(a[1]); b[2] = sm4Sbox(a[2]); b[3] = sm4Sbox(a[3]);GET_ULONG_BE(bb,b,0) c =bb^(ROTL(bb, 2))^(ROTL(bb, 10))^(ROTL(bb, 18))^(ROTL(bb, 24)); return c;}/* * private F function: * Calculating and getting encryption/decryption contents. * args: [in] x0: original contents; * args: [in] x1: original contents; * args: [in] x2: original contents; * args: [in] x3: original contents; * args: [in] rk: encryption/decryption key; * return the contents of encryption/decryption contents. */static unsigned long sm4F(unsigned long x0, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long rk){ return (x0^sm4Lt(x1^x2^x3^rk));}/* private function: * Calculating round encryption key. * args: [in] a: a is a 32 bits unsigned value; * return: sk[i]: i{0,1,2,3,...31}. */static unsigned long sm4CalciRK(unsigned long ka){ unsigned long bb = 0; unsigned long rk = 0; unsigned char a[4]; unsigned char b[4]; PUT_ULONG_BE(ka,a,0) b[0] = sm4Sbox(a[0]); b[1] = sm4Sbox(a[1]); b[2] = sm4Sbox(a[2]); b[3] = sm4Sbox(a[3]);GET_ULONG_BE(bb,b,0) rk = bb^(ROTL(bb, 13))^(ROTL(bb, 23)); return rk;}static void sm4_setkey( unsigned long SK[32], unsigned char key[16] ){ unsigned long MK[4]; unsigned long k[36]; unsigned long i = 0; GET_ULONG_BE( MK[0], key, 0 ); GET_ULONG_BE( MK[1], key, 4 ); GET_ULONG_BE( MK[2], key, 8 ); GET_ULONG_BE( MK[3], key, 12 ); k[0] = MK[0]^FK[0]; k[1] = MK[1]^FK[1]; k[2] = MK[2]^FK[2]; k[3] = MK[3]^FK[3]; for(; i<32; i++) { k[i+4] = k[i] ^ (sm4CalciRK(k[i+1]^k[i+2]^k[i+3]^CK[i])); SK[i] = k[i+4];}}/* * SM4 standard one round processing * */static void sm4_one_round( unsigned long sk[32], unsigned char input[16], unsigned char output[16] ){ unsigned long i = 0; unsigned long ulbuf[36]; memset(ulbuf, 0, sizeof(ulbuf)); GET_ULONG_BE( ulbuf[0], input, 0 ) GET_ULONG_BE( ulbuf[1], input, 4 ) GET_ULONG_BE( ulbuf[2], input, 8 ) GET_ULONG_BE( ulbuf[3], input, 12 ) while(i<32) { ulbuf[i+4] = sm4F(ulbuf[i], ulbuf[i+1], ulbuf[i+2], ulbuf[i+3], sk[i]);// #ifdef _DEBUG// printf("rk(%02d) = 0x%08x, X(%02d) = 0x%08x \n",i,sk[i], i, ulbuf[i+4] );// #endif i++; }PUT_ULONG_BE(ulbuf[35],output,0);PUT_ULONG_BE(ulbuf[34],output,4);PUT_ULONG_BE(ulbuf[33],output,8);PUT_ULONG_BE(ulbuf[32],output,12);}/* * SM4 key schedule (128-bit, encryption) */void sm4_setkey_enc( sm4_context *ctx, unsigned char key[16] ){ ctx->mode = SM4_ENCRYPT;sm4_setkey( ctx->sk, key );}/* * SM4 key schedule (128-bit, decryption) */void sm4_setkey_dec( sm4_context *ctx, unsigned char key[16] ){ int i;ctx->mode = SM4_ENCRYPT; sm4_setkey( ctx->sk, key ); for( i = 0; i < 16; i ++ ) { SWAP( ctx->sk[ i ], ctx->sk[ 31-i] ); }}/* * SM4-ECB block encryption/decryption */void sm4_crypt_ecb( sm4_context *ctx, int mode, int length, unsigned char *input, unsigned char *output){ while( length > 0 ) { sm4_one_round( ctx->sk, input, output ); input += 16; output += 16; length -= 16; }}
