public EllipticDiffieHellman(EllipticCurve curve, CurvePoint generator, IntX order, byte[] priv = null)
{
this.curve = curve;
this.generator = generator;
// Generate private key
if (priv == null)
{
byte[] max = order.ToArray();
do
{
byte[] p1 = new byte[5 /*rand.Next(max.Length) + 1*/];
rand.GetBytes(p1);
if (p1.Length == max.Length)
{
p1[p1.Length - 1] %= max[max.Length - 1];
}
else
{
p1[p1.Length - 1] &= 127;
}
this.priv = DHHelper.FromArray(p1);
} while (this.priv < 2);
}
else
{
this.priv = DHHelper.FromArray(priv);
}
// Generate public key
pub = curve.Multiply(generator, this.priv);
}
public byte[] GetSharedSecret(byte[] pK)
{
byte[] p1 = new byte[pK[0] | (pK[1] << 8) | (pK[2] << 16) | (pK[3] << 24)]; // Reconstruct x-axis size
byte[] p2 = new byte[pK.Length - p1.Length - 4];
Array.Copy(pK, 4, p1, 0, p1.Length);
Array.Copy(pK, 4 + p1.Length, p2, 0, p2.Length);
CurvePoint remotePublic = new CurvePoint(DHHelper.FromArray(p1), DHHelper.FromArray(p2));
byte[] secret = curve.Multiply(remotePublic, priv).X.ToArray(); // Use the x-coordinate as the shared secret
// PBKDF2-HMAC-SHA1 (Common shared secret generation method)
return(new Rfc2898DeriveBytes(secret, Encoding.UTF8.GetBytes("P1sN0R4inb0wPl5P1sPls"), 1000).GetBytes(32));
}
