//KEY GENERATION ALGORITHM IN DIFFIE-HELLMAN KEY EXCHANGE PROTOCOL
void KeyGeneration(long int *q, long int *alpha, long int *private_key, long int *public_key)
{
long int p;
if(print_flag1)
printf("\n selecting q->\n\r");
while(1)
{
srand((unsigned int) time(NULL));
p = random() % LARGE;
if( p <= 10000) continue;
/* test for even number */
if ( (p & 0x01) == 0 ) continue;
/* Trivial divisibility test by primes 3, 5, 7, 11, 13, 17, 19 */
if ( (p % 3 == 0 ) || (p % 5 == 0) || (p % 7 == 0) || (p % 11 == 0 )
|| (p % 13 == 0) || ( p % 17 == 0) || ( p% 19 == 0) )
continue;
if( MillerRobinTest(p, MAX_ITERATION) )
break;
}
*q = p;
if (verify_prime(p) )
printf( "q = %ld is prime\n", *q);
else {
printf("q = %ld is composite\n", *q);
exit(0);
}
/* Select a primitive root of q */
*alpha = primitive_root( p );
/* Select a private key < q randomly */
*private_key = rand() % p;
/* Compute the public key */
*public_key = ModPower(*alpha, *private_key, *q);
}
//KEY GENERATION ALGORITHM IN RSA CRYPTOSYSTEM.
void KeyGeneration(key *pub_key, key *pvt_key)
{
long int p,q;
long int n;
long int phi_n;
long int e;
// Select p and q which are primes and p<q.
if(print_flag1)
printf("\n selecting p->\n\r");
while(1)
{
srand((unsigned int) time(NULL));
p = random() % LARGE;
/* test for even number */
if ( p & 0x01 == 0 ) continue;
if(MillerRobinTest(p, MAX_ITERATION))
break;
}
if(print_flag1)
printf("\n selecting q->\n\r");
while(1)
{
srand((unsigned int) time(NULL));
q=random() % LARGE;
if( q == p)
{
srand((unsigned int) time(NULL));
q = random() % LARGE;
continue;
}
if(MillerRobinTest(q, MAX_ITERATION))
break;
}
// Compute n.
if (verify_prime(p) && verify_prime(q) )
printf("p = %ld, q = %ld are primes\n", p, q);
else {
//exit(0);
return recall_key(pub_key, pvt_key);
}
printf("p = %ld, q = %ld\n", p, q);
n = p * q;
// Compute Euler's phi(totient) function
phi_n = (p-1)*(q-1);
// Compute e such that gcd(e,phi_n(n))=1.
if(print_flag1)
printf("\n selcting e->\n\r");
while(1)
{
e = random()%phi_n;
if(gcd(e, phi_n)==1)
break;
}
// Compute d such that ed=1(mod phi_n(n)).
if(print_flag1)
printf("\n selceting d->\n\r");
extended_euclid(1, 0, phi_n, 0, 1, e);
if(mul_inverse <0) {
mul_inverse = - mul_inverse;
mul_inverse = ((phi_n - 1 ) * mul_inverse) mod phi_n;
}
if(print_flag1)
printf("\n phi_n= %ld\n\n",phi_n);
// Put Public Key and Private Key.
pub_key->public_key.n = n;
pub_key->public_key.e = e;
pvt_key->private_key.n = n;
pvt_key->private_key.d = mul_inverse;
} // end of KeyGeneraion()
