KMac
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Utilities;
using System;
namespace Org.BouncyCastle.Crypto.Macs
{
public class KMac : IMac, IXof, IDigest
{
private static readonly byte[] padding = new byte[100];
private readonly CShakeDigest cshake;
private readonly int bitLength;
private readonly int outputLength;
private byte[] key;
private bool initialised;
private bool firstOutput;
public string AlgorithmName => "KMAC" + cshake.AlgorithmName.Substring(6);
public KMac(int bitLength, byte[] S)
{
cshake = new CShakeDigest(bitLength, Strings.ToAsciiByteArray("KMAC"), S);
this.bitLength = bitLength;
outputLength = bitLength * 2 / 8;
}
public void BlockUpdate(byte[] input, int inOff, int len)
{
if (!initialised)
throw new InvalidOperationException("KMAC not initialized");
cshake.BlockUpdate(input, inOff, len);
}
public int DoFinal(byte[] output, int outOff)
{
if (firstOutput) {
if (!initialised)
throw new InvalidOperationException("KMAC not initialized");
byte[] array = XofUtilities.RightEncode(GetMacSize() * 8);
cshake.BlockUpdate(array, 0, array.Length);
}
int result = cshake.OutputFinal(output, outOff, GetMacSize());
Reset();
return result;
}
public int OutputFinal(byte[] output, int outOff, int outLen)
{
if (firstOutput) {
if (!initialised)
throw new InvalidOperationException("KMAC not initialized");
byte[] array = XofUtilities.RightEncode(outLen * 8);
cshake.BlockUpdate(array, 0, array.Length);
}
int result = cshake.OutputFinal(output, outOff, outLen);
Reset();
return result;
}
public int Output(byte[] output, int outOff, int outLen)
{
if (firstOutput) {
if (!initialised)
throw new InvalidOperationException("KMAC not initialized");
byte[] array = XofUtilities.RightEncode(0);
cshake.BlockUpdate(array, 0, array.Length);
firstOutput = false;
}
return cshake.Output(output, outOff, outLen);
}
public int GetByteLength()
{
return cshake.GetByteLength();
}
public int GetDigestSize()
{
return outputLength;
}
public int GetMacSize()
{
return outputLength;
}
public void Init(ICipherParameters parameters)
{
KeyParameter keyParameter = (KeyParameter)parameters;
key = Arrays.Clone(keyParameter.GetKey());
initialised = true;
Reset();
}
public void Reset()
{
cshake.Reset();
if (key != null) {
if (bitLength == 128)
bytePad(key, 168);
else
bytePad(key, 136);
}
firstOutput = true;
}
private void bytePad(byte[] X, int w)
{
byte[] array = XofUtilities.LeftEncode(w);
BlockUpdate(array, 0, array.Length);
byte[] array2 = encode(X);
BlockUpdate(array2, 0, array2.Length);
int num = w - (array.Length + array2.Length) % w;
if (num > 0 && num != w) {
while (num > padding.Length) {
BlockUpdate(padding, 0, padding.Length);
num -= padding.Length;
}
BlockUpdate(padding, 0, num);
}
}
private static byte[] encode(byte[] X)
{
return Arrays.Concatenate(XofUtilities.LeftEncode(X.Length * 8), X);
}
public void Update(byte input)
{
if (!initialised)
throw new InvalidOperationException("KMAC not initialized");
cshake.Update(input);
}
}
}