using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
namespace Org.BouncyCastle.Crypto.Agreement{
/**
* P1363 7.2.1 ECSVDP-DH
*
* ECSVDP-DH is Elliptic Curve Secret Value Derivation Primitive,
* Diffie-Hellman version. It is based on the work of [DH76], [Mil86],
* and [Kob87]. This primitive derives a shared secret value from one
* party's private key and another party's public key, where both have
* the same set of EC domain parameters. If two parties correctly
* execute this primitive, they will produce the same output. This
* primitive can be invoked by a scheme to derive a shared secret key;
* specifically, it may be used with the schemes ECKAS-DH1 and
* DL/ECKAS-DH2. It assumes that the input keys are valid (see also
* Section 7.2.2).
*/
public class ECDHBasicAgreement
: IBasicAgreement
{
protected internal ECPrivateKeyParameters privKey;
public void Init(
ICipherParameters parameters)
{
if (parameters is ParametersWithRandom)
{
parameters = ((ParametersWithRandom)parameters).Parameters;
}
this.privKey = (ECPrivateKeyParameters)parameters;
}
public virtual BigInteger CalculateAgreement(
ICipherParameters pubKey)
{
ECPublicKeyParameters pub = (ECPublicKeyParameters) pubKey;
ECPoint P = pub.Q.Multiply(privKey.D);
// if ( p.IsInfinity ) throw new Exception("d*Q == infinity");
return P.X.ToBigInteger();
}
}
}
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