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Built on the nucleus of TweetNaCl, TweetPepper provides contemporary key formats, key protection using SCrypt/SecretBox, digital signature support scheme featuring CubeHash, key encapsulation using Salsa20, and other useful features you probably want anyway.

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/*
 Copyright (c) 2000-2015 The Legion of the Bouncy Castle Inc. (http://www.bouncycastle.org)
Copyright 2016, David R. Smith, All Rights Reserved

This file is part of TweetPepper.

TweetPepper is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

TweetPepper is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with TweetPepper.  If not, see .

 */
package com.cryptoregistry.digest.sha3;

import com.cryptoregistry.digest.sha3.Xof;

/**
 * implementation of SHAKE based on following KeccakNISTInterface.c from
 * http://keccak.noekeon.org/
 * 
 * Following the naming conventions used in the C source code to enable easy
 * review of the implementation.
 */
public class SHAKEDigest extends KeccakDigest implements Xof {
	private static int checkBitLength(int bitLength) {
		switch (bitLength) {
		case 128:
		case 256:
			return bitLength;
		default:
			throw new IllegalArgumentException("'bitLength' " + bitLength
					+ " not supported for SHAKE");
		}
	}

	public SHAKEDigest() {
		this(128);
	}

	public SHAKEDigest(int bitLength) {
		super(checkBitLength(bitLength));
	}

	public SHAKEDigest(SHAKEDigest source) {
		super(source);
	}

	public String getAlgorithmName() {
		return "SHAKE" + fixedOutputLength;
	}

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

	public int doFinal(byte[] out, int outOff, int outLen) {
		int length = doOutput(out, outOff, outLen);

		reset();

		return length;
	}

	public int doOutput(byte[] out, int outOff, int outLen) {
		if (!squeezing) {
			absorb(new byte[] { 0x0F }, 0, 4);
		}

		squeeze(out, outOff, ((long) outLen) * 8);

		return outLen;
	}

	/*
	 * TODO Possible API change to support partial-byte suffixes.
	 */
	protected int doFinal(byte[] out, int outOff, byte partialByte,
			int partialBits) {
		return doFinal(out, outOff, getDigestSize(), partialByte, partialBits);
	}

	/*
	 * TODO Possible API change to support partial-byte suffixes.
	 */
	protected int doFinal(byte[] out, int outOff, int outLen, byte partialByte,
			int partialBits) {
		if (partialBits < 0 || partialBits > 7) {
			throw new IllegalArgumentException(
					"'partialBits' must be in the range [0,7]");
		}

		int finalInput = (partialByte & ((1 << partialBits) - 1))
				| (0x0F << partialBits);
		int finalBits = partialBits + 4;

		if (finalBits >= 8) {
			oneByte[0] = (byte) finalInput;
			absorb(oneByte, 0, 8);
			finalBits -= 8;
			finalInput >>>= 8;
		}

		if (finalBits > 0) {
			oneByte[0] = (byte) finalInput;
			absorb(oneByte, 0, finalBits);
		}

		squeeze(out, outOff, ((long) outLen) * 8);

		reset();

		return outLen;
	}
}