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using System;
using System.Collections;
using System.IO;
using System.Text;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Crypto.Signers;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
namespace Org.BouncyCastle.Crypto.Signers
{
public class Gost3410DigestSigner
: ISigner
{
private readonly IDigest digest;
private readonly IDsa dsaSigner;
private bool forSigning;
public Gost3410DigestSigner(
IDsa signer,
IDigest digest)
{
this.dsaSigner = signer;
this.digest = digest;
}
public string AlgorithmName
{
get { return digest.AlgorithmName + "with" + dsaSigner.AlgorithmName; }
}
public void Init(
bool forSigning,
ICipherParameters parameters)
{
this.forSigning = forSigning;
AsymmetricKeyParameter k;
if (parameters is ParametersWithRandom)
{
k = (AsymmetricKeyParameter)((ParametersWithRandom)parameters).Parameters;
}
else
{
k = (AsymmetricKeyParameter)parameters;
}
if (forSigning && !k.IsPrivate)
{
throw new InvalidKeyException("Signing Requires Private Key.");
}
if (!forSigning && k.IsPrivate)
{
throw new InvalidKeyException("Verification Requires Public Key.");
}
Reset();
dsaSigner.Init(forSigning, parameters);
}
/**
* update the internal digest with the byte b
*/
public void Update(
byte input)
{
digest.Update(input);
}
/**
* update the internal digest with the byte array in
*/
public void BlockUpdate(
byte[] input,
int inOff,
int length)
{
digest.BlockUpdate(input, inOff, length);
}
/**
* Generate a signature for the message we've been loaded with using
* the key we were initialised with.
*/
public byte[] GenerateSignature()
{
if (!forSigning)
throw new InvalidOperationException("GOST3410DigestSigner not initialised for signature generation.");
byte[] hash = new byte[digest.GetDigestSize()];
digest.DoFinal(hash, 0);
try
{
BigInteger[] sig = dsaSigner.GenerateSignature(hash);
byte[] sigBytes = new byte[64];
// TODO Add methods to allow writing BigInteger to existing byte array?
byte[] r = sig[0].ToByteArrayUnsigned();
byte[] s = sig[1].ToByteArrayUnsigned();
s.CopyTo(sigBytes, 32 - s.Length);
r.CopyTo(sigBytes, 64 - r.Length);
return sigBytes;
}
catch (Exception e)
{
throw new SignatureException(e.Message, e);
}
}
/// <returns>true if the internal state represents the signature described in the passed in array.</returns>
public bool VerifySignature(
byte[] signature)
{
if (forSigning)
throw new InvalidOperationException("DSADigestSigner not initialised for verification");
byte[] hash = new byte[digest.GetDigestSize()];
digest.DoFinal(hash, 0);
BigInteger R, S;
try
{
R = new BigInteger(1, signature, 32, 32);
S = new BigInteger(1, signature, 0, 32);
}
catch (Exception e)
{
throw new SignatureException("error decoding signature bytes.", e);
}
return dsaSigner.VerifySignature(hash, R, S);
}
/// <summary>Reset the internal state</summary>
public void Reset()
{
digest.Reset();
}
}
}
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