const Primality::key_type Primality::prime_by_miller_rabin(key_type max)
{
do
{
prime = get_random_integer(max);
}
while(!miller_rabin_test(prime));
return prime;
}
CryptoPpDlogZpSafePrime::CryptoPpDlogZpSafePrime(ZpGroupParams * groupParams, mt19937 prg)
{
mt19937 prime_gen(clock()); // prg for prime checking
this->random_element_gen = prg;
biginteger p = groupParams->getP();
biginteger q = groupParams->getQ();
biginteger g = groupParams->getXg();
// if p is not 2q+1 throw exception
if (!(q * 2 + 1 == p)) {
throw invalid_argument("p must be equal to 2q+1");
}
// if p is not a prime throw exception
if (!miller_rabin_test(p, 40, prime_gen)) {
throw invalid_argument("p must be a prime");
}
// if q is not a prime throw exception
if (!miller_rabin_test(q, 40, prime_gen)) {
throw invalid_argument("q must be a prime");
}
// set the inner parameters
this->groupParams = groupParams;
//Create CryptoPP Dlog group with p, ,q , g.
//The validity of g will be checked after the creation of the group because the check need the pointer to the group
pointerToGroup = new CryptoPP::DL_GroupParameters_GFP_DefaultSafePrime();
pointerToGroup->Initialize(biginteger_to_cryptoppint(p), biginteger_to_cryptoppint(q), biginteger_to_cryptoppint(g));
//If the generator is not valid, delete the allocated memory and throw exception
if (!pointerToGroup->ValidateElement(3, biginteger_to_cryptoppint(g), 0)){
delete pointerToGroup;
throw invalid_argument("generator value is not valid");
}
//Create the GroupElement - generator with the pointer that return from the native function
generator = new ZpSafePrimeElementCryptoPp(g, p, false);
//Now that we have p, we can calculate k which is the maximum length of a string to be converted to a Group Element of this group.
k = calcK(p);
}
