#include <openssl/dh.h>
#include <memory.h>
int main()
{
DH *d1,*d2;
BIO *b;
int ret,size,i,len1,len2;
charsharekey1[128],sharekey2[128];
/* 构造DH数据结构 */
d1=DH_new();
d2=DH_new();
/* 生成d1的密钥参数，该密钥参数是可以公开的 */
ret=DH_generate_parameters_ex(d1,64,DH_GENERATOR_2,NULL);
if(ret!=1)
{
printf("DH_generate_parameters_ex err!\n");
return -1;
}
/* 检查密钥参数 */
ret=DH_check(d1,&i);
if(ret!=1)
{
printf("DH_check err!\n");
if(i&DH_CHECK_P_NOT_PRIME)
printf("p value is not prime\n");
if(i&DH_CHECK_P_NOT_SAFE_PRIME)
printf("p value is not a safe prime\n");
if (i&DH_UNABLE_TO_CHECK_GENERATOR)
printf("unable to check the generator value\n");
if (i&DH_NOT_SUITABLE_GENERATOR)
printf("the g value is not a generator\n");
}
printf("DH parameters appear to be ok.\n");
/* 密钥大小 */
size=DH_size(d1);
printf("DH key1 size : %d\n",size);
/* 生成公私钥 */
ret=DH_generate_key(d1);
if(ret!=1)
{
printf("DH_generate_key err!\n");
return -1;
}
/* p和g为公开的密钥参数，因此可以拷贝 */
d2->p=BN_dup(d1->p);
d2->g=BN_dup(d1->g);
/* 生成公私钥,用于测试生成共享密钥 */
ret=DH_generate_key(d2);
if(ret!=1)
{
printf("DH_generate_key err!\n");
return -1;
}
/* 检查公钥 */
ret=DH_check_pub_key(d1,d1->pub_key,&i);
if(ret!=1)
{
if (i&DH_CHECK_PUBKEY_TOO_SMALL)
printf("pub key too small \n");
if (i&DH_CHECK_PUBKEY_TOO_LARGE)
printf("pub key too large \n");
}
/* 计算共享密钥 */
len1=DH_compute_key(sharekey1,d2->pub_key,d1);
len2=DH_compute_key(sharekey2,d1->pub_key,d2);
if(len1!=len2)
{
printf("生成共享密钥失败1\n");
return -1;
}
if(memcmp(sharekey1,sharekey2,len1)!=0)
{
printf("生成共享密钥失败2\n");
return -1;
}
printf("生成共享密钥成功\n");
b=BIO_new(BIO_s_file());
BIO_set_fp(b,stdout,BIO_NOCLOSE);
/* 打印密钥 */
DHparams_print(b,d1);
BIO_free(b);
DH_free(d1);
DH_free(d2);
return 0;
}
本例主要演示了生成DH密钥以及密钥交换函数。