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Jingtum SDK
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/*
 * Copyright www.jingtum.com Inc. 
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package com.jingtum.core.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.bouncycastle.crypto.digests.RIPEMD160Digest;

public class HashUtils {
    private static final MessageDigest digest;
    static {
        try {
            digest = MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);  // Can't happen.
        }
    }

    /**
     * See {@link HashUtils#doubleDigest(byte[], int, int)}.
     * @param input Input byte array to be hashed
     * @return hash of the input byte in Big Endian form
     */
    public static byte[] doubleDigest(byte[] input) {
        return doubleDigest(input, 0, input.length);
    }

    /**
     * Calculates the SHA-256 hash of the given byte range, and then hashes the resulting hash again. This is
     * standard procedure in Bitcoin. The resulting hash is in big endian form.
     * @param input Input byte array to be hashed
     * @param offset the offset to start from in the array of bytes.
     * @param length the number of bytes to use, starting at
     * {@code offset}.
     * @return hash of the input byte in Big Endian form
     */
    public static byte[] doubleDigest(byte[] input, int offset, int length) {
        synchronized (digest) {
            digest.reset();
            digest.update(input, offset, length);
            byte[] first = digest.digest();
            return digest.digest(first);
        }
    }

    /**
     * Calculates the SHA-256 hash of the given byte range, and then hashes the resulting hash again. This is
     * standard procedure in Bitcoin. The resulting hash is in big endian form.
     * @param input Input byte array to be hashed
     * @return hash of the input byte in Big Endian form
     */
    public static byte[] SHA256_RIPEMD160(byte[] input) {
        try {
            byte[] sha256 = MessageDigest.getInstance("SHA-256").digest(input);
            RIPEMD160Digest digest = new RIPEMD160Digest();
            digest.update(sha256, 0, sha256.length);
            byte[] out = new byte[20];
            digest.doFinal(out, 0);
            return out;
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);  // Cannot happen.
        }
    }
}