/// <summary>
/// Calculates B.
/// </summary>
/// <param name="N"></param>
/// <param name="g"></param>
/// <param name="b"></param>
/// <param name="v"></param>
/// <returns></returns>
public static NetBigInteger CalcB(NetBigInteger N, NetBigInteger g, NetBigInteger b, NetBigInteger v)
{
//B = k*v + g^b % N
NetBigInteger k = Calck(N, g);
return((k.Multiply(v).Add(g.ModPow(b, N))).Mod(N));
}
/// <summary>
/// Calculates server's S.
/// </summary>
/// <param name="N"></param>
/// <param name="A"></param>
/// <param name="v"></param>
/// <param name="u"></param>
/// <param name="b"></param>
/// <returns></returns>
public static NetBigInteger CalcSServer(NetBigInteger N, NetBigInteger A, NetBigInteger v, NetBigInteger u, NetBigInteger b)
{
// Host: S = (Av^u) ^ b (computes session key)
NetBigInteger S = (A.Multiply(v.ModPow(u, N))).ModPow(b, N);
return(S);
}
/// <summary>
/// Calculates client's S.
/// </summary>
/// <param name="N"></param>
/// <param name="g"></param>
/// <param name="B"></param>
/// <param name="k"></param>
/// <param name="x"></param>
/// <param name="a"></param>
/// <param name="u"></param>
/// <returns></returns>
public static NetBigInteger CalcSClient(NetBigInteger N, NetBigInteger g, NetBigInteger B, NetBigInteger k, NetBigInteger x, NetBigInteger a, NetBigInteger u)
{
// <premaster secret> = (B - (k * g^x)) ^ (a + (u * x)) % N
// (B + (N - ((k*g.ModExp(x,N))%N))) - Do it this way. Thanks Valery.
NetBigInteger S = (B.Add(N.Subtract((k.Multiply(g.ModPow(x, N))).Mod(N)))).ModPow(a.Add(u.Multiply(x)), N);
return(S);
}
/// <summary>
/// Compute server ephemeral value (B)
/// </summary>
public static byte[] ComputeServerEphemeral(byte[] serverPrivateEphemeral, byte[] verifier) // b
{
var b = new NetBigInteger(NetUtility.ToHexString(serverPrivateEphemeral), 16);
var v = new NetBigInteger(NetUtility.ToHexString(verifier), 16);
// B = kv + g^b (mod N)
var bb = g.ModPow(b, N);
var kv = v.Multiply(k);
var B = (kv.Add(bb)).Mod(N);
return(B.ToByteArrayUnsigned());
}
public static byte[] ComputeClientSessionValue(byte[] serverPublicEphemeral, byte[] xdata, byte[] udata, byte[] clientPrivateEphemeral)
{
// (B - kg^x) ^ (a + ux) (mod N)
var B = new NetBigInteger(NetUtility.ToHexString(serverPublicEphemeral), 16);
var x = new NetBigInteger(NetUtility.ToHexString(xdata), 16);
var u = new NetBigInteger(NetUtility.ToHexString(udata), 16);
var a = new NetBigInteger(NetUtility.ToHexString(clientPrivateEphemeral), 16);
var bx = g.ModPow(x, N);
var btmp = B.Add(N.Multiply(k)).Subtract(bx.Multiply(k)).Mod(N);
return(btmp.ModPow(x.Multiply(u).Add(a), N).ToByteArrayUnsigned());
}
/// <summary>
/// Computes the client session value
/// </summary>
public static byte[] ComputeClientSessionValue(byte[] serverPublicEphemeral, byte[] xdata, byte[] udata, byte[] clientPrivateEphemeral)
{
// (B - kg^x) ^ (a + ux) (mod N)
var B = new NetBigInteger(NetUtility.ToHexString(serverPublicEphemeral), 16);
var x = new NetBigInteger(NetUtility.ToHexString(xdata), 16);
var u = new NetBigInteger(NetUtility.ToHexString(udata), 16);
var a = new NetBigInteger(NetUtility.ToHexString(clientPrivateEphemeral), 16);
var bx = g.ModPow(x, N);
var btmp = B.Add(N.Multiply(k)).Subtract(bx.Multiply(k)).Mod(N);
return btmp.ModPow(x.Multiply(u).Add(a), N).ToByteArrayUnsigned();
}
/// <summary>
/// Compute server ephemeral value (B)
/// </summary>
public static byte[] ComputeServerEphemeral(byte[] serverPrivateEphemeral, byte[] verifier) // b
{
var b = new NetBigInteger(NetUtility.ToHexString(serverPrivateEphemeral), 16);
var v = new NetBigInteger(NetUtility.ToHexString(verifier), 16);
// B = kv + g^b (mod N)
var bb = g.ModPow(b, N);
var kv = v.Multiply(k);
var B = (kv.Add(bb)).Mod(N);
return B.ToByteArrayUnsigned();
}
/// <summary>
/// Calculates server's S.
/// </summary>
/// <param name="N"></param>
/// <param name="A"></param>
/// <param name="v"></param>
/// <param name="u"></param>
/// <param name="b"></param>
/// <returns></returns>
public static NetBigInteger CalcSServer(NetBigInteger N, NetBigInteger A, NetBigInteger v, NetBigInteger u, NetBigInteger b)
{
// Host: S = (Av^u) ^ b (computes session key)
NetBigInteger S = (A.Multiply(v.ModPow(u, N))).ModPow(b, N);
return S;
}
/// <summary>
/// Calculates client's S.
/// </summary>
/// <param name="N"></param>
/// <param name="g"></param>
/// <param name="B"></param>
/// <param name="k"></param>
/// <param name="x"></param>
/// <param name="a"></param>
/// <param name="u"></param>
/// <returns></returns>
public static NetBigInteger CalcSClient(NetBigInteger N, NetBigInteger g, NetBigInteger B, NetBigInteger k, NetBigInteger x, NetBigInteger a, NetBigInteger u)
{
// <premaster secret> = (B - (k * g^x)) ^ (a + (u * x)) % N
// (B + (N - ((k*g.ModExp(x,N))%N))) - Do it this way. Thanks Valery.
NetBigInteger S = (B.Add(N.Subtract((k.Multiply(g.ModPow(x, N))).Mod(N)))).ModPow(a.Add(u.Multiply(x)), N);
return S;
}
