http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
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package org.bouncycastle.pqc.crypto.qtesla;

import org.bouncycastle.crypto.digests.CSHAKEDigest;
import org.bouncycastle.crypto.digests.SHAKEDigest;

class HashUtils
{

    public static final int SECURE_HASH_ALGORITHM_KECCAK_128_RATE = 168;
    public static final int SECURE_HASH_ALGORITHM_KECCAK_256_RATE = 136;

    
Description:	The Secure-Hash-Algorithm-3 Extendable-Output Function That Generally Supports 128 Bits of Security Strength, If the Output is Sufficiently Long

/***************************************************************************************************************************************************************
     * Description:	The Secure-Hash-Algorithm-3 Extendable-Output Function That Generally Supports 128 Bits of Security Strength, If the Output is Sufficiently Long
     ***************************************************************************************************************************************************************/
    static void secureHashAlgorithmKECCAK128(byte[] output, int outputOffset, int outputLength, byte[] input, int inputOffset, int inputLength)
    {
        SHAKEDigest dig = new SHAKEDigest(128);
        dig.update(input, inputOffset, inputLength);

        dig.doFinal(output, outputOffset, outputLength);
    }

    
Description:	The Secure-Hash-Algorithm-3 Extendable-Output Function That Generally Supports 256 Bits of Security Strength, If the Output is Sufficiently Long

/***************************************************************************************************************************************************************
     * Description:	The Secure-Hash-Algorithm-3 Extendable-Output Function That Generally Supports 256 Bits of Security Strength, If the Output is Sufficiently Long
     ***************************************************************************************************************************************************************/
    static void secureHashAlgorithmKECCAK256(byte[] output, int outputOffset, int outputLength, byte[] input, int inputOffset, int inputLength)
    {
        SHAKEDigest dig = new SHAKEDigest(256);
        dig.update(input, inputOffset, inputLength);

        dig.doFinal(output, outputOffset, outputLength);
    }

    /* Customizable Secure Hash Algorithm KECCAK 128 / Customizable Secure Hash Algorithm KECCAK 256 */


    static void customizableSecureHashAlgorithmKECCAK128Simple(byte[] output, int outputOffset, int outputLength, short continuousTimeStochasticModelling, byte[] input, int inputOffset, int inputLength)
    {
        CSHAKEDigest dig = new CSHAKEDigest(128, null, new byte[] {(byte)continuousTimeStochasticModelling, (byte)(continuousTimeStochasticModelling >> 8) });
        dig.update(input, inputOffset, inputLength);

        dig.doFinal(output, outputOffset, outputLength);
    }

    static void customizableSecureHashAlgorithmKECCAK256Simple(byte[] output, int outputOffset, int outputLength, short continuousTimeStochasticModelling, byte[] input, int inputOffset, int inputLength)
    {
        CSHAKEDigest dig = new CSHAKEDigest(256, null, new byte[] {(byte)continuousTimeStochasticModelling, (byte)(continuousTimeStochasticModelling >> 8) });
        dig.update(input, inputOffset, inputLength);

        dig.doFinal(output, outputOffset, outputLength);
    }
}