internal static BigInteger ComputeX(ClientInfo clientInfo, Session session)
{
var method = session.SrpMethod;
var iterations = session.Iterations;
if (iterations == 0)
{
throw ExceptionFactory.MakeUnsupported("SRP: 0 iterations is not supported");
}
// TODO: Add constants for 1024, 6144 and 8192
if (method != "SRPg-4096")
{
throw ExceptionFactory.MakeUnsupported(
string.Format("SRP: method '{0}' is not supported", method));
}
var k1 = Crypto.Hkdf(method: method,
ikm: session.Salt,
salt: clientInfo.Username.ToBytes());
var k2 = Crypto.Pbes2(method: session.KeyMethod,
password: clientInfo.Password,
salt: k1,
iterations: iterations);
var x = clientInfo.AccountKey.CombineWith(k2);
return(x.ToBigInt());
}
public static byte[] Pbes2(string method, string password, byte[] salt, int iterations)
{
switch (method)
{
case "PBES2-HS256":
case "PBES2g-HS256":
return(Pbkdf2.GenerateSha256(password.ToBytes(), salt, iterations, 32));
case "PBES2-HS512":
case "PBES2g-HS512":
return(Pbkdf2.GenerateSha512(password.ToBytes(), salt, iterations, 32));
}
throw ExceptionFactory.MakeUnsupported(
string.Format("PBES2: method '{0}' is not supported", method));
}
