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using System;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
using Org.BouncyCastle.Math.EC.Multiplier;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Signers
{
/**
* GOST R 34.10-2001 Signature Algorithm
*/
public class ECGost3410Signer
: IDsaExt
{
private ECKeyParameters key;
private SecureRandom random;
private bool forSigning;
public virtual string AlgorithmName
{
get { return key.AlgorithmName; }
}
public virtual void Init(
bool forSigning,
ICipherParameters parameters)
{
this.forSigning = forSigning;
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 ECPrivateKeyParameters))
throw new InvalidKeyException("EC private key required for signing");
this.key = (ECPrivateKeyParameters) parameters;
}
else
{
if (!(parameters is ECPublicKeyParameters))
throw new InvalidKeyException("EC public key required for verification");
this.key = (ECPublicKeyParameters)parameters;
}
}
public virtual BigInteger Order
{
get { return key.Parameters.N; }
}
/**
* 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 virtual BigInteger[] GenerateSignature(
byte[] message)
{
if (!forSigning)
{
throw new InvalidOperationException("not initialized for signing");
}
byte[] mRev = Arrays.Reverse(message); // conversion is little-endian
BigInteger e = new BigInteger(1, mRev);
ECDomainParameters ec = key.Parameters;
BigInteger n = ec.N;
BigInteger d = ((ECPrivateKeyParameters)key).D;
BigInteger r, s = null;
ECMultiplier basePointMultiplier = CreateBasePointMultiplier();
do // generate s
{
BigInteger k;
do // generate r
{
do
{
k = new BigInteger(n.BitLength, random);
}
while (k.SignValue == 0);
ECPoint p = basePointMultiplier.Multiply(ec.G, k).Normalize();
r = p.AffineXCoord.ToBigInteger().Mod(n);
}
while (r.SignValue == 0);
s = (k.Multiply(e)).Add(d.Multiply(r)).Mod(n);
}
while (s.SignValue == 0);
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 virtual bool VerifySignature(
byte[] message,
BigInteger r,
BigInteger s)
{
if (forSigning)
{
throw new InvalidOperationException("not initialized for verification");
}
byte[] mRev = Arrays.Reverse(message); // conversion is little-endian
BigInteger e = new BigInteger(1, mRev);
BigInteger n = key.Parameters.N;
// r in the range [1,n-1]
if (r.CompareTo(BigInteger.One) < 0 || r.CompareTo(n) >= 0)
{
return false;
}
// s in the range [1,n-1]
if (s.CompareTo(BigInteger.One) < 0 || s.CompareTo(n) >= 0)
{
return false;
}
BigInteger v = BigIntegers.ModOddInverseVar(n, e);
BigInteger z1 = s.Multiply(v).Mod(n);
BigInteger z2 = (n.Subtract(r)).Multiply(v).Mod(n);
ECPoint G = key.Parameters.G; // P
ECPoint Q = ((ECPublicKeyParameters)key).Q;
ECPoint point = ECAlgorithms.SumOfTwoMultiplies(G, z1, Q, z2).Normalize();
if (point.IsInfinity)
return false;
BigInteger R = point.AffineXCoord.ToBigInteger().Mod(n);
return R.Equals(r);
}
protected virtual ECMultiplier CreateBasePointMultiplier()
{
return new FixedPointCombMultiplier();
}
}
}
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