SM2算法第十五篇：ECDSA数字签名算法的C语言实现

#include <string.h>

#include <stdio.h>

#include <openssl/ec.h>

#include <openssl/ssl.h>

#include <openssl/ecdsa.h>

#include <openssl/objects.h>

#include <openssl/err.h>

int    main()

{

EC_KEY              *key1,*key2;

EC_POINT            *pubkey1,*pubkey2;

EC_GROUP            *group1,*group2;

int                 ret,nid,size,i,sig_len;

unsigned char*      signature,digest[20];

BIO                 *berr;

EC_builtin_curve    *curves;

int                 crv_len;

char                shareKey1[128],shareKey2[128];

int                 len1,len2;

/* 构造EC_KEY数据结构 */

key1=EC_KEY_new();

if(key1==NULL)

{

printf("EC_KEY_new err!\n");

return -1;

}

key2=EC_KEY_new();

if(key2==NULL)

{

printf("EC_KEY_new err!\n");

return -1;

}

/* 获取实现的椭圆曲线个数 */

crv_len = EC_get_builtin_curves(NULL, 0);

curves = (EC_builtin_curve *)malloc(sizeof(EC_builtin_curve) * crv_len);

/* 获取椭圆曲线列表 */

EC_get_builtin_curves(curves, crv_len);

/*

nid=curves[0].nid;会有错误，原因是密钥太短

*/

/* 选取一种椭圆曲线 */

nid=curves[25].nid;

/* 根据选择的椭圆曲线生成密钥参数group */

group1=EC_GROUP_new_by_curve_name(nid);

if(group1==NULL)

{

printf("EC_GROUP_new_by_curve_name err!\n");

return -1;

}

group2=EC_GROUP_new_by_curve_name(nid);

if(group1==NULL)

{

printf("EC_GROUP_new_by_curve_name err!\n");

return -1;

}

/* 设置密钥参数 */

ret=EC_KEY_set_group(key1,group1);

if(ret!=1)

{

printf("EC_KEY_set_group err.\n");

return -1;

}

ret=EC_KEY_set_group(key2,group2);

if(ret!=1)

{

printf("EC_KEY_set_group err.\n");

return -1;

}

/* 生成密钥 */

ret=EC_KEY_generate_key(key1);

if(ret!=1)

{

printf("EC_KEY_generate_key err.\n");

return -1;

}

ret=EC_KEY_generate_key(key2);

if(ret!=1)

{

printf("EC_KEY_generate_key err.\n");

return -1;

}

/* 检查密钥 */

ret=EC_KEY_check_key(key1);

if(ret!=1)

{

printf("check key err.\n");

return -1;

}

/* 获取密钥大小 */

size=ECDSA_size(key1);

printf("size %d \n",size);

for(i=0;i<20;i++)

memset(&digest[i],i+1,1);

signature=(unsigned char *)malloc(size);

ERR_load_crypto_strings();

berr=BIO_new(BIO_s_file());

BIO_set_fp(berr,stdout,BIO_NOCLOSE);

/* 签名数据，本例未做摘要，可将digest中的数据看作是sha1摘要结果 */

ret=ECDSA_sign(0,digest,20,signature,(unsigned int *)&sig_len,key1);

if(ret!=1)

{

ERR_print_errors(berr);

printf("sign err!\n");

return -1;

}

/* 验证签名 */

ret=ECDSA_verify(0,digest,20,signature,sig_len,key1);

if(ret!=1)

{

ERR_print_errors(berr);

printf("ECDSA_verify err!\n");

return -1;

}

/* 获取对方公钥，不能直接引用 */

pubkey2 = (struct ec_point_st *)EC_KEY_get0_public_key(key2);

/* 生成一方的共享密钥 */

len1=ECDH_compute_key(shareKey1, 128, pubkey2, key1, NULL);

pubkey1 = (struct ec_point_st *)EC_KEY_get0_public_key(key1);

/* 生成另一方共享密钥 */

len2=ECDH_compute_key(shareKey2, 128, pubkey1, key2, NULL);

if(len1!=len2)

{

printf("err\n");

}

else

{

ret=memcmp(shareKey1,shareKey2,len1);

if(ret==0)

printf("生成共享密钥成功\n");

else

printf("生成共享密钥失败\n");

}

printf("test ok!\n");

BIO_free(berr);

EC_KEY_free(key1);

EC_KEY_free(key2);

free(signature);

free(curves);

return 0;

}