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 vector
sm4_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 testing
sm4_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 __cplusplus
extern "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;
}
}