The DH algorithm in OpenSSL demo

Tag:openssl   demo    animated    

/* The following program utilizes the OpenSSL library to implement the DH algorithm, generate keys and calculate 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];    /* Construct DH data structure */d1=dh_new ();    D2=dh_new ();       /* Generate key parameters for D1 */RET=DH_GENERATE_PARAMETERS_EX (d1,64,dh_generator_2,null);        if (ret!=1) {//prime_len,g is greater than 1, common 2 and 5 printf ("Dh_generate_parameters_ex err!\n");    return-1;    }/* Check key parameters */Ret=dh_check (d1,&i);//i is set to 0 first, then through or equal to, get error message type 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"); /* Key size*/size=dh_size (D1);    printf ("DH key1 Size:%d\n", size);    /* Generate Public private key */Ret=dh_generate_key (D1);        if (ret!=1) {printf ("Dh_generate_key err!\n");    return-1;    }/* p and G are public key parameters, so you can copy */D2->p=bn_dup (D1-&GT;P);    D2->g=bn_dup (D1-&GT;G);    /* Generate a public private key for testing the generated shared key */Ret=dh_generate_key (D2);        if (ret!=1) {printf ("Dh_generate_key err!\n");    return-1;    }/* Check public key */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");    }/* Compute shared Key */Len1=dh_compute_key (SHAREKEY1,D2-&GT;PUB_KEY,D1);    Len2=dh_compute_key (SHAREKEY2,D1-&GT;PUB_KEY,D2);        if (len1!=len2) {printf ("Generate shared Key failed 1\n");    return-1;        } if (memcmp (SHAREKEY1,SHAREKEY2,LEN1)!=0) {printf ("Generate shared Key failed 2\n");    return-1;    } printf ("Generate shared key successfully \ n"); return 0;}

The DH algorithm in OpenSSL demo