OpensslにおけるdhアルゴリズムDemo

/*      openssl ，   dh  ，        sessionkey*/
#include <openssl/dh.h>
#include <memory.h>
int main() {
    DH *d1,*d2;
    BIO *b;
    int ret,size,i,len1,len2;
    char sharekey1[128],sharekey2[128];
    /*   DH      */
    d1=DH_new();
    d2=DH_new();
    /*   d1      */
    ret=DH_generate_parameters_ex(d1,64,DH_GENERATOR_2,NULL);   
    if(ret!=1) {               //prime_len，g  1，  2 5
        printf("DH_generate_parameters_ex err!
");
        return -1;
    }
    /*        */
    ret=DH_check(d1,&i);//i   0,       ,        
    if(ret!=1) {
        printf("DH_check err!
");
    if(i&DH_CHECK_P_NOT_PRIME)
        printf("p value is not prime
");
    if(i&DH_CHECK_P_NOT_SAFE_PRIME)
        printf("p value is not a safe prime
");
    if (i&DH_UNABLE_TO_CHECK_GENERATOR)
        printf("unable to check the generator value
");
    if (i&DH_NOT_SUITABLE_GENERATOR)
        printf("the g value is not a generator
");
    }
    printf("DH parameters appear to be ok.
");
    /*      */
    size=DH_size(d1);
    printf("DH key1 size : %d
",size);
    /*       */
    ret=DH_generate_key(d1);
    if(ret!=1) {
        printf("DH_generate_key err!
");
        return -1;
    }
    /* p g        ，       */
    d2->p=BN_dup(d1->p);
    d2->g=BN_dup(d1->g);
    /*      ,           */
    ret=DH_generate_key(d2);
    if(ret!=1) {
        printf("DH_generate_key err!
");
        return -1;
    }
    /*      */
    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 
");
        if (i&DH_CHECK_PUBKEY_TOO_LARGE)
            printf("pub key too large 
");
    }
    /*        */
    len1=DH_compute_key(sharekey1,d2->pub_key,d1);
    len2=DH_compute_key(sharekey2,d1->pub_key,d2);
    if(len1!=len2) {
        printf("        1
");
        return -1;
    }
    if(memcmp(sharekey1,sharekey2,len1)!=0) {
        printf("        2
");
        return -1;
    }
    printf("        
");
    return 0;
}