io.takamaka.crypto.digests.SHAKEDigest Maven / Gradle / Ivy

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This package contains an old version of the qtesla algorithm from the bouncycastle library. Changes have been introduced in the current library that make the old keys incompatible with the new ones. The purpose of this package is to maintain, within the takamaka.io software, compatibility with the old implementation of signature keys.

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 */
package io.takamaka.crypto.digests;

import io.takamaka.crypto.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);
    }

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

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

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

        reset();

        return length;
    }

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

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

        return outLen;
    }

    /*
     * TODO Possible API change to support partial-byte suffixes.
     */
    @Override
    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) {
            absorb(new byte[]{(byte) finalInput}, 0, 1);
            finalBits -= 8;
            finalInput >>>= 8;
        }

        if (finalBits > 0) {
            absorbBits(finalInput, finalBits);
        }

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

        reset();

        return outLen;
    }
}