59 lines
2.0 KiB
C#
59 lines
2.0 KiB
C#
using System;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Math.EC;
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using Org.BouncyCastle.Security;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.Parameters;
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namespace Org.BouncyCastle.Crypto.Agreement
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{
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/**
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* P1363 7.2.2 ECSVDP-DHC
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*
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* ECSVDP-DHC is Elliptic Curve Secret Value Derivation Primitive,
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* Diffie-Hellman version with cofactor multiplication. It is based on
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* the work of [DH76], [Mil86], [Kob87], [LMQ98] and [Kal98a]. This
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* primitive derives a shared secret value from one party's private key
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* and another party's public key, where both have the same set of EC
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* domain parameters. If two parties correctly execute this primitive,
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* they will produce the same output. This primitive can be invoked by a
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* scheme to derive a shared secret key; specifically, it may be used
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* with the schemes ECKAS-DH1 and DL/ECKAS-DH2. It does not assume the
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* validity of the input public key (see also Section 7.2.1).
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* <p>
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* Note: As stated P1363 compatibility mode with ECDH can be preset, and
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* in this case the implementation doesn't have a ECDH compatibility mode
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* (if you want that just use ECDHBasicAgreement and note they both implement
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* BasicAgreement!).</p>
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*/
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public class ECDHCBasicAgreement
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: IBasicAgreement
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{
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private ECPrivateKeyParameters key;
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public void Init(
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ICipherParameters parameters)
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{
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if (parameters is ParametersWithRandom)
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{
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parameters = ((ParametersWithRandom) parameters).Parameters;
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}
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this.key = (ECPrivateKeyParameters)parameters;
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}
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public BigInteger CalculateAgreement(
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ICipherParameters pubKey)
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{
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ECPublicKeyParameters pub = (ECPublicKeyParameters) pubKey;
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ECDomainParameters parameters = pub.Parameters;
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ECPoint P = pub.Q.Multiply(parameters.H.Multiply(key.D));
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// if ( p.IsInfinity ) throw new Exception("Invalid public key");
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return P.X.ToBigInteger();
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}
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}
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}
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