SM4国密对称算法源码解析

最近在研究国密算法，主要分为：SM2、SM3、SM4。其中SM2为非对称加密算法，SM3为哈希摘要算法，SM4为对称加密算法。

1.在SM4算法源文件中主要有以下几个函数：

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 );

2.还有一个重要的结构体：

/*** \brief          SM4 context structure*/
typedef struct
{int mode;                   /*!<  encrypt/decrypt   */unsigned long sk[32];       /*!<  SM4 subkeys       */
}
sm4_context;

结构体中的mode参数控制加密还是解密，其中mode=1为加密，mode=0为解密。数组sk为轮密钥。SM4为32轮加密变换。

3.加密函数：

 /*** \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])；

这个函数是用来加密明文的，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。

4.解密函数：

/*** \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] );

这个函数为解密函数，是进行密文解密的。参数与加密函数一样。

5.ECB工作模式：

/*** \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);

这个函数的作用是使用ECB模式（ECB（Electronic Codebook，电码本），ECB模式是分组密码的一种最基本的工作模式。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。

6. CBC工作模式：

/*** \brief          SM4-CBC buffer encryption/decryption* \param ctx      SM4 context* \param mode     SM4_ENCRYPT or SM4_DECRYPT* \param length   length of the input data* \param iv       initialization vector (updated after use)* \param input    buffer holding the input data* \param output   buffer holding the output data*/
void sm4_crypt_cbc( sm4_context *ctx, int mode, int length,unsigned char iv[16],unsigned char *input,unsigned char *output );

以上就是SM4加密算法的函数简介，具体的代码实现可不用掌握，下面是完整代码：

7.sm4.h头文件

/*** \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);/*** \brief          SM4-CBC buffer encryption/decryption* \param ctx      SM4 context* \param mode     SM4_ENCRYPT or SM4_DECRYPT* \param length   length of the input data* \param iv       initialization vector (updated after use)* \param input    buffer holding the input data* \param output   buffer holding the output data*/
void sm4_crypt_cbc( sm4_context *ctx,int mode,int length,unsigned char iv[16],unsigned char *input,unsigned char *output );#ifdef __cplusplus
}
#endif#endif /* sm4.h */

8.sm4.c源文件

/** 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] );
// #endifi++;}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;}}/** SM4-CBC buffer encryption/decryption*/
void sm4_crypt_cbc( sm4_context *ctx,int mode,int length,unsigned char iv[16],unsigned char *input,unsigned char *output )
{int i;unsigned char temp[16];if( mode == SM4_ENCRYPT ){while( length > 0 ){for( i = 0; i < 16; i++ )output[i] = (unsigned char)( input[i] ^ iv[i] );sm4_one_round( ctx->sk, output, output );memcpy( iv, output, 16 );input  += 16;output += 16;length -= 16;}}else /* SM4_DECRYPT */{while( length > 0 ){memcpy( temp, input, 16 );sm4_one_round( ctx->sk, input, output );for( i = 0; i < 16; i++ )output[i] = (unsigned char)( output[i] ^ iv[i] );memcpy( iv, temp, 16 );input  += 16;output += 16;length -= 16;}}
}

9.测试文件

/** 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");//decrypt 1M times testing vector based on standards.i = 0;sm4_setkey_enc(&ctx,key);while (i<1000000) {sm4_crypt_ecb(&ctx,1,16,input,input);i++;}for(i=0;i<16;i++)printf("%02x ", input[i]);printf("\n");return 0;
}

 

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