package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.digests.SkeinEngine;
import org.bouncycastle.crypto.engines.ThreefishEngine;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.SkeinParameters;

Implementation of the Skein parameterised MAC function in 256, 512 and 1024 bit block sizes, based on the Threefish tweakable block cipher. 

This is the 1.3 version of Skein defined in the Skein hash function submission to the NIST SHA-3
competition in October 2010.

Skein was designed by Niels Ferguson - Stefan Lucks - Bruce Schneier - Doug Whiting - Mihir
Bellare - Tadayoshi Kohno - Jon Callas - Jesse Walker.
See Also:
SkeinEngine
SkeinParameters/**
 * Implementation of the Skein parameterised MAC function in 256, 512 and 1024 bit block sizes,
 * based on the {@link ThreefishEngine Threefish} tweakable block cipher.
 * <p>
 * This is the 1.3 version of Skein defined in the Skein hash function submission to the NIST SHA-3
 * competition in October 2010.
 * <p>
 * Skein was designed by Niels Ferguson - Stefan Lucks - Bruce Schneier - Doug Whiting - Mihir
 * Bellare - Tadayoshi Kohno - Jon Callas - Jesse Walker.
 *
 * @see SkeinEngine
 * @see SkeinParameters
 */
public class SkeinMac
    implements Mac
{
    
256 bit block size - Skein MAC-256
/**
     * 256 bit block size - Skein MAC-256
     */
    public static final int SKEIN_256 = SkeinEngine.SKEIN_256;
    
512 bit block size - Skein MAC-512
/**
     * 512 bit block size - Skein MAC-512
     */
    public static final int SKEIN_512 = SkeinEngine.SKEIN_512;
    
1024 bit block size - Skein MAC-1024
/**
     * 1024 bit block size - Skein MAC-1024
     */
    public static final int SKEIN_1024 = SkeinEngine.SKEIN_1024;

    private SkeinEngine engine;

    
Constructs a Skein MAC with an internal state size and output size.
Params:
stateSizeBits –  the internal state size in bits - one of SKEIN_256, SKEIN_512 or SKEIN_1024.
digestSizeBits – the output/MAC size to produce in bits, which must be an integral number of bytes./**
     * Constructs a Skein MAC with an internal state size and output size.
     *
     * @param stateSizeBits  the internal state size in bits - one of {@link #SKEIN_256}, {@link #SKEIN_512} or
     *                       {@link #SKEIN_1024}.
     * @param digestSizeBits the output/MAC size to produce in bits, which must be an integral number of bytes.
     */
    public SkeinMac(int stateSizeBits, int digestSizeBits)
    {
        this.engine = new SkeinEngine(stateSizeBits, digestSizeBits);
    }

    public SkeinMac(SkeinMac mac)
    {
        this.engine = new SkeinEngine(mac.engine);
    }

    public String getAlgorithmName()
    {
        return "Skein-MAC-" + (engine.getBlockSize() * 8) + "-" + (engine.getOutputSize() * 8);
    }

    
Initialises the Skein digest with the provided parameters.
 See SkeinParameters for details on the parameterisation of the Skein hash function. 
Params:
params – an instance of SkeinParameters or KeyParameter./**
     * Initialises the Skein digest with the provided parameters.<br>
     * See {@link SkeinParameters} for details on the parameterisation of the Skein hash function.
     *
     * @param params an instance of {@link SkeinParameters} or {@link KeyParameter}.
     */
    public void init(CipherParameters params)
        throws IllegalArgumentException
    {
        SkeinParameters skeinParameters;
        if (params instanceof SkeinParameters)
        {
            skeinParameters = (SkeinParameters)params;
        }
        else if (params instanceof KeyParameter)
        {
            skeinParameters = new SkeinParameters.Builder().setKey(((KeyParameter)params).getKey()).build();
        }
        else
        {
            throw new IllegalArgumentException("Invalid parameter passed to Skein MAC init - "
                + params.getClass().getName());
        }
        if (skeinParameters.getKey() == null)
        {
            throw new IllegalArgumentException("Skein MAC requires a key parameter.");
        }
        engine.init(skeinParameters);
    }

    public int getMacSize()
    {
        return engine.getOutputSize();
    }

    public void reset()
    {
        engine.reset();
    }

    public void update(byte in)
    {
        engine.update(in);
    }

    public void update(byte[] in, int inOff, int len)
    {
        engine.update(in, inOff, len);
    }

    public int doFinal(byte[] out, int outOff)
    {
        return engine.doFinal(out, outOff);
    }

}