HMacDsaKCalculator.cs
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using System;
using Org.BouncyCastle.Crypto.Macs;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Signers
{
/**
* A deterministic K calculator based on the algorithm in section 3.2 of RFC 6979.
*/
public class HMacDsaKCalculator
: IDsaKCalculator
{
private readonly HMac hMac;
private readonly byte[] K;
private readonly byte[] V;
private BigInteger n;
/**
* Base constructor.
*
* @param digest digest to build the HMAC on.
*/
public HMacDsaKCalculator(IDigest digest)
{
this.hMac = new HMac(digest);
this.V = new byte[hMac.GetMacSize()];
this.K = new byte[hMac.GetMacSize()];
}
public virtual bool IsDeterministic
{
get { return true; }
}
public virtual void Init(BigInteger n, SecureRandom random)
{
throw new InvalidOperationException("Operation not supported");
}
public void Init(BigInteger n, BigInteger d, byte[] message)
{
this.n = n;
Arrays.Fill(V, (byte)0x01);
Arrays.Fill(K, (byte)0);
byte[] x = new byte[(n.BitLength + 7) / 8];
byte[] dVal = BigIntegers.AsUnsignedByteArray(d);
Array.Copy(dVal, 0, x, x.Length - dVal.Length, dVal.Length);
byte[] m = new byte[(n.BitLength + 7) / 8];
BigInteger mInt = BitsToInt(message);
if (mInt.CompareTo(n) >= 0)
{
mInt = mInt.Subtract(n);
}
byte[] mVal = BigIntegers.AsUnsignedByteArray(mInt);
Array.Copy(mVal, 0, m, m.Length - mVal.Length, mVal.Length);
hMac.Init(new KeyParameter(K));
hMac.BlockUpdate(V, 0, V.Length);
hMac.Update((byte)0x00);
hMac.BlockUpdate(x, 0, x.Length);
hMac.BlockUpdate(m, 0, m.Length);
hMac.DoFinal(K, 0);
hMac.Init(new KeyParameter(K));
hMac.BlockUpdate(V, 0, V.Length);
hMac.DoFinal(V, 0);
hMac.BlockUpdate(V, 0, V.Length);
hMac.Update((byte)0x01);
hMac.BlockUpdate(x, 0, x.Length);
hMac.BlockUpdate(m, 0, m.Length);
hMac.DoFinal(K, 0);
hMac.Init(new KeyParameter(K));
hMac.BlockUpdate(V, 0, V.Length);
hMac.DoFinal(V, 0);
}
public virtual BigInteger NextK()
{
byte[] t = new byte[((n.BitLength + 7) / 8)];
for (;;)
{
int tOff = 0;
while (tOff < t.Length)
{
hMac.BlockUpdate(V, 0, V.Length);
hMac.DoFinal(V, 0);
int len = System.Math.Min(t.Length - tOff, V.Length);
Array.Copy(V, 0, t, tOff, len);
tOff += len;
}
BigInteger k = BitsToInt(t);
if (k.SignValue > 0 && k.CompareTo(n) < 0)
{
return k;
}
hMac.BlockUpdate(V, 0, V.Length);
hMac.Update((byte)0x00);
hMac.DoFinal(K, 0);
hMac.Init(new KeyParameter(K));
hMac.BlockUpdate(V, 0, V.Length);
hMac.DoFinal(V, 0);
}
}
private BigInteger BitsToInt(byte[] t)
{
BigInteger v = new BigInteger(1, t);
if (t.Length * 8 > n.BitLength)
{
v = v.ShiftRight(t.Length * 8 - n.BitLength);
}
return v;
}
}
}