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using System;
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 readonly int size;
private int halfSize;
private bool forSigning;
public Gost3410DigestSigner(IDsa signer, IDigest digest)
{
this.dsaSigner = signer;
this.digest = digest;
halfSize = digest.GetDigestSize();
this.size = halfSize * 2;
}
public virtual string AlgorithmName
{
get { return digest.AlgorithmName + "with" + dsaSigner.AlgorithmName; }
}
public virtual 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);
}
public virtual void Update(byte input)
{
digest.Update(input);
}
public virtual void BlockUpdate(byte[] input, int inOff, int inLen)
{
digest.BlockUpdate(input, inOff, inLen);
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public virtual void BlockUpdate(ReadOnlySpan<byte> input)
{
digest.BlockUpdate(input);
}
#endif
public virtual 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[size];
// TODO Add methods to allow writing BigInteger to existing byte array?
byte[] r = sig[0].ToByteArrayUnsigned();
byte[] s = sig[1].ToByteArrayUnsigned();
s.CopyTo(sigBytes, halfSize - s.Length);
r.CopyTo(sigBytes, size - r.Length);
return sigBytes;
}
catch (Exception e)
{
throw new SignatureException(e.Message, e);
}
}
public virtual 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, halfSize, halfSize);
S = new BigInteger(1, signature, 0, halfSize);
}
catch (Exception e)
{
throw new SignatureException("error decoding signature bytes.", e);
}
return dsaSigner.VerifySignature(hash, R, S);
}
public virtual void Reset()
{
digest.Reset();
}
}
}
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