1 files changed, 132 insertions, 0 deletions
diff --git a/Crypto/src/crypto/signers/GOST3410Signer.cs b/Crypto/src/crypto/signers/GOST3410Signer.cs
new file mode 100644
index 000000000..375eeb5cc
--- /dev/null
+++ b/Crypto/src/crypto/signers/GOST3410Signer.cs
@@ -0,0 +1,132 @@
+using System;
+
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Crypto.Signers
+{
+	/**
+	 * Gost R 34.10-94 Signature Algorithm
+	 */
+	public class Gost3410Signer
+		: IDsa
+	{
+		private Gost3410KeyParameters key;
+		private SecureRandom random;
+
+		public string AlgorithmName
+		{
+			get { return "GOST3410"; }
+		}
+
+		public void Init(
+			bool				forSigning,
+			ICipherParameters	parameters)
+		{
+			if (forSigning)
+			{
+				if (parameters is ParametersWithRandom)
+				{
+					ParametersWithRandom rParam = (ParametersWithRandom)parameters;
+
+					this.random = rParam.Random;
+					parameters = rParam.Parameters;
+				}
+				else
+				{
+					this.random = new SecureRandom();
+				}
+
+				if (!(parameters is Gost3410PrivateKeyParameters))
+					throw new InvalidKeyException("GOST3410 private key required for signing");
+
+				this.key = (Gost3410PrivateKeyParameters) parameters;
+			}
+			else
+			{
+				if (!(parameters is Gost3410PublicKeyParameters))
+					throw new InvalidKeyException("GOST3410 public key required for signing");
+
+				this.key = (Gost3410PublicKeyParameters) parameters;
+			}
+		}
+
+		/**
+		 * generate a signature for the given message using the key we were
+		 * initialised with. For conventional Gost3410 the message should be a Gost3411
+		 * hash of the message of interest.
+		 *
+		 * @param message the message that will be verified later.
+		 */
+		public BigInteger[] GenerateSignature(
+			byte[] message)
+		{
+			byte[] mRev = new byte[message.Length]; // conversion is little-endian
+			for (int i = 0; i != mRev.Length; i++)
+			{
+				mRev[i] = message[mRev.Length - 1 - i];
+			}
+
+			BigInteger m = new BigInteger(1, mRev);
+			Gost3410Parameters parameters = key.Parameters;
+			BigInteger k;
+
+			do
+			{
+				k = new BigInteger(parameters.Q.BitLength, random);
+			}
+			while (k.CompareTo(parameters.Q) >= 0);
+
+			BigInteger r = parameters.A.ModPow(k, parameters.P).Mod(parameters.Q);
+
+			BigInteger s = k.Multiply(m).
+				Add(((Gost3410PrivateKeyParameters)key).X.Multiply(r)).
+				Mod(parameters.Q);
+
+			return new BigInteger[]{ r, s };
+		}
+
+		/**
+		 * return true if the value r and s represent a Gost3410 signature for
+		 * the passed in message for standard Gost3410 the message should be a
+		 * Gost3411 hash of the real message to be verified.
+		 */
+		public bool VerifySignature(
+			byte[]		message,
+			BigInteger	r,
+			BigInteger	s)
+		{
+			byte[] mRev = new byte[message.Length]; // conversion is little-endian
+			for (int i = 0; i != mRev.Length; i++)
+			{
+				mRev[i] = message[mRev.Length - 1 - i];
+			}
+
+			BigInteger m = new BigInteger(1, mRev);
+			Gost3410Parameters parameters = key.Parameters;
+
+			if (r.SignValue < 0 || parameters.Q.CompareTo(r) <= 0)
+			{
+				return false;
+			}
+
+			if (s.SignValue < 0 || parameters.Q.CompareTo(s) <= 0)
+			{
+				return false;
+			}
+
+			BigInteger v = m.ModPow(parameters.Q.Subtract(BigInteger.Two), parameters.Q);
+
+			BigInteger z1 = s.Multiply(v).Mod(parameters.Q);
+			BigInteger z2 = (parameters.Q.Subtract(r)).Multiply(v).Mod(parameters.Q);
+
+			z1 = parameters.A.ModPow(z1, parameters.P);
+			z2 = ((Gost3410PublicKeyParameters)key).Y.ModPow(z2, parameters.P);
+
+			BigInteger u = z1.Multiply(z2).Mod(parameters.P).Mod(parameters.Q);
+
+			return u.Equals(r);
+		}
+	}
+}