public byte[] CalculateSharedSecret(byte[] otherPublicKey)
{
var output = new byte[32];
X25519.CalculateAgreement(_XprivateKey, 0, otherPublicKey, 0, output, 0);
return(output);
}
public void GenerateSecret(X25519PublicKeyParameters publicKey, byte[] buf, int off)
{
byte[] encoded = new byte[X25519.PointSize];
publicKey.Encode(encoded, 0);
if (!X25519.CalculateAgreement(data, 0, encoded, 0, buf, off))
{
throw new InvalidOperationException("X25519 agreement failed");
}
}
protected static byte[] ECDH_GenerateSecret(OneKey[] keys)
{
if (keys[0][CoseKeyKeys.KeyType].Type != CBORType.Number)
{
throw new CoseException("Not an EC Key");
}
if (keys[1][CoseKeyKeys.KeyType].Type != CBORType.Number)
{
throw new CoseException("Not an EC Key");
}
OneKey epkPub = keys[1];
OneKey epkPriv = keys[0];
byte[] temp;
switch ((GeneralValuesInt)epkPub[CoseKeyKeys.KeyType].AsInt32())
{
case GeneralValuesInt.KeyType_OKP:
if (epkPub[CoseKeyParameterKeys.OKP_Curve].AsInt32() != epkPriv[CoseKeyParameterKeys.OKP_Curve].AsInt32())
{
throw new CoseException("Not a match of curves");
}
switch ((GeneralValuesInt)epkPriv[CoseKeyParameterKeys.OKP_Curve].AsInt32())
{
case GeneralValuesInt.X25519:
temp = X25519.CalculateAgreement(epkPub.AsBytes(CoseKeyParameterKeys.OKP_X), epkPriv.AsBytes(CoseKeyParameterKeys.OKP_D));
break;
default:
throw new CoseException("Not a supported Curve");
}
return(temp);
case GeneralValuesInt.KeyType_EC2:
if (epkPub[CoseKeyParameterKeys.EC_Curve].AsInt32() != epkPriv[CoseKeyParameterKeys.EC_Curve].AsInt32())
{
throw new CoseException("not a match of curves");
}
// Get the curve
X9ECParameters p = epkPub.GetCurve();
ECPoint pubPoint = epkPub.GetPoint();
ECDomainParameters parameters = new ECDomainParameters(p.Curve, p.G, p.N, p.H);
ECPublicKeyParameters pub = new ECPublicKeyParameters(pubPoint, parameters);
ECPrivateKeyParameters priv = new ECPrivateKeyParameters(epkPriv.AsBigInteger(CoseKeyParameterKeys.EC_D), parameters);
IBasicAgreement e1 = new ECDHBasicAgreement();
e1.Init(priv);
BigInteger k1 = e1.CalculateAgreement(pub);
return(PadBytes(k1.ToByteArrayUnsigned(), p.Curve.FieldSize));
default:
throw new CoseException("Not an EC Key");
}
}
