public static void dh(NetworkStream s, StreamReader r, StreamWriter w)
{
try
{
// Diffie hellman key exchange on GF(P)
// genererate
byte[] rand = positive(Convert.FromBase64String(getSalt(128)));
BigInteger a = new BigInteger(rand);
// send g**secret to the server
BigInteger g_a = BigInteger.ModPow(G, a, P);
byte[] g_a_byte = g_a.ToByteArray().Reverse().ToArray();
w.WriteLine(base64_encode(g_a_byte));
w.Flush();
BigInteger g_b = new BigInteger(positive(Convert.FromBase64String(r.ReadLine()).Reverse().ToArray()));
// read g_b and compute g_b_a
// compute g_b_a
byte[] secret = BigInteger.ModPow(g_b, a, P).ToByteArray().Reverse().ToArray();
if (secret.Length != 128)
{
byte[] temp = new byte[128];
Array.Copy(secret, 1, temp, 0, 128);
Array.Copy(temp, secret, 128);
}
SHA256Managed sha = new SHA256Managed();
dh_secret = sha.ComputeHash(secret, 0, 128);
}
catch (Exception)
{
// DH error
OtherThread.disconnect();
}
// DONE DIFFIE HELLMAN
}
