/*
* Create a DH private key
*/
DH_PrivateKey::DH_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
m_group = grp;
if(x_arg == 0)
{
const BigInt& p = group_p();
m_x.randomize(rng, dl_exponent_size(p.bits()));
}
else
{
m_x = x_arg;
}
if(m_y == 0)
{
m_y = power_mod(group_g(), m_x, group_p());
}
}
/*
* DL_Group Constructor
*/
DL_Group::DL_Group(RandomNumberGenerator& rng,
PrimeType type, size_t pbits, size_t qbits)
{
if(pbits < 1024)
throw Invalid_Argument("DL_Group: prime size " + std::to_string(pbits) +
" is too small");
if(type == Strong)
{
m_p = random_safe_prime(rng, pbits);
m_q = (m_p - 1) / 2;
m_g = 2;
}
else if(type == Prime_Subgroup)
{
if(!qbits)
qbits = dl_exponent_size(pbits);
m_q = random_prime(rng, qbits);
BigInt X;
while(m_p.bits() != pbits || !is_prime(m_p, rng))
{
X.randomize(rng, pbits);
m_p = X - (X % (2*m_q) - 1);
}
m_g = make_dsa_generator(m_p, m_q);
}
else if(type == DSA_Kosherizer)
{
qbits = qbits ? qbits : ((pbits <= 1024) ? 160 : 256);
generate_dsa_primes(rng, m_p, m_q, pbits, qbits);
m_g = make_dsa_generator(m_p, m_q);
}
m_initialized = true;
}