bool DH::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const
{
Integer w(otherPublicKey, PublicKeyLength());
if (validateOtherPublicKey && !(w > 1 && w < p && Jacobi(w, p) == 1))
return false;
Integer s(privateKey, PrivateKeyLength());
Integer z = a_exp_b_mod_c(w, s, p);
z.Encode(agreedValue, AgreedValueLength());
return true;
}
bool XTR_DH::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const
{
GFP2Element w(otherPublicKey, PublicKeyLength());
if (validateOtherPublicKey)
{
GFP2_ONB<ModularArithmetic> gfp2(m_p);
GFP2Element three = gfp2.ConvertIn(3);
if (w.c1.IsNegative() || w.c2.IsNegative() || w.c1 >= m_p || w.c2 >= m_p || w == three)
return false;
if (XTR_Exponentiate(w, m_q, m_p) != three)
return false;
}
Integer s(privateKey, PrivateKeyLength());
GFP2Element z = XTR_Exponentiate(w, s, m_p);
z.Encode(agreedValue, AgreedValueLength());
return true;
}
