Initial Commit

iTechSharp/srcbc/crypto/agreement/ECDHCBasicAgreement.cs

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+using System;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.EC;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace Org.BouncyCastle.Crypto.Agreement
+{
+    /**
+     * P1363 7.2.2 ECSVDP-DHC
+     *
+     * ECSVDP-DHC is Elliptic Curve Secret Value Derivation Primitive,
+     * Diffie-Hellman version with cofactor multiplication. It is based on
+     * the work of [DH76], [Mil86], [Kob87], [LMQ98] and [Kal98a]. 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 does not assume the
+     * validity of the input public key (see also Section 7.2.1).
+     * <p>
+     * Note: As stated P1363 compatibility mode with ECDH can be preset, and
+     * in this case the implementation doesn't have a ECDH compatibility mode
+     * (if you want that just use ECDHBasicAgreement and note they both implement
+     * BasicAgreement!).</p>
+     */
+    public class ECDHCBasicAgreement
+		: IBasicAgreement
+    {
+        private ECPrivateKeyParameters key;
+
+        public void Init(
+            ICipherParameters parameters)
+        {
+			if (parameters is ParametersWithRandom)
+			{
+				parameters = ((ParametersWithRandom) parameters).Parameters;
+			}
+
+			this.key = (ECPrivateKeyParameters)parameters;
+        }
+
+        public BigInteger CalculateAgreement(
+            ICipherParameters pubKey)
+        {
+            ECPublicKeyParameters pub = (ECPublicKeyParameters) pubKey;
+            ECDomainParameters parameters = pub.Parameters;
+            ECPoint P = pub.Q.Multiply(parameters.H.Multiply(key.D));
+
+            // if ( p.IsInfinity ) throw new Exception("Invalid public key");
+
+            return P.X.ToBigInteger();
+        }
+    }
+
+}