/// <summary>
/// Create a shared secret between this key and another.
/// </summary>
/// <param name="other"></param>
/// <returns></returns>
public byte[] GenerateSharedSecret(EphermalKey other)
{
var agreement = AgreementUtilities.GetBasicAgreement("ECDH");
agreement.Init(privateKey);
return(agreement
.CalculateAgreement(other.publicKey)
.ToByteArrayUnsigned());
}
/// <summary>
/// Create a shared secret between this key and another.
/// </summary>
/// <param name="other">
/// Another ephermal key.
/// </param>
/// <returns>
/// The shared secret as a byte array.
/// </returns>
/// <remarks>
/// Uses the ECDH agreement algorithm to generate the shared secet.
/// </remarks>
public byte[] GenerateSharedSecret(EphermalKey other)
{
var agreement = AgreementUtilities.GetBasicAgreement("ECDH");
agreement.Init(privateKey);
var secret = agreement.CalculateAgreement(other.publicKey);
return(BigIntegers.AsUnsignedByteArray(agreement.GetFieldSize(), secret));
}
public void SharedSecret()
{
var curve = "P-256";
var alice = EphermalKey.Generate(curve);
var bob = EphermalKey.Generate(curve);
var aliceSecret = alice.GenerateSharedSecret(bob);
var bobSecret = bob.GenerateSharedSecret(alice);
CollectionAssert.AreEqual(aliceSecret, bobSecret);
Assert.AreEqual(32, aliceSecret.Length);
}