Java Key Pair Create generateKeyDigest(int keyLength, String password)

Description

generate Key Digest

License

Apache License

Declaration

public static byte[] generateKeyDigest(int keyLength, String password) 

Method Source Code

//package com.java2s;
/*/*from  ww  w  . j a v  a  2s.c om*/
 * Copyright 2017 ZhangJiupeng
 *
 * Licensed 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.
 */

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import java.util.Arrays;

public class Main {
    public static byte[] generateKeyDigest(int keyLength, String password) {
        try {
            MessageDigest digester = MessageDigest.getInstance("MD5");
            int length = (keyLength + 15) / 16 * 16;
            byte[] passwordBytes = password.getBytes("UTF-8");
            byte[] temp = digester.digest(passwordBytes);
            byte[] key = Arrays.copyOf(temp, length);
            for (int i = 1; i < length / 16; i++) {
                temp = Arrays.copyOf(temp, 16 + passwordBytes.length);
                System.arraycopy(passwordBytes, 0, temp, 16, passwordBytes.length);
                System.arraycopy(digester.digest(temp), 0, key, i * 16, 16);
            }
            return Arrays.copyOf(key, keyLength);
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return new byte[keyLength];
    }

    public static byte[] getBytes(int length, int value) {
        if (length < 1 || length > 4)
            throw new RuntimeException("bad length");
        byte[] bytes = new byte[4];
        bytes[0] = (byte) ((value >> 24) & 0xff);
        bytes[1] = (byte) ((value >> 16) & 0xff);
        bytes[2] = (byte) ((value >> 8) & 0xff);
        bytes[3] = (byte) (value & 0xff);
        if (length == 4)
            return bytes;
        else
            return Arrays.copyOfRange(bytes, 4 - length, 4);
    }

    public static byte[] getBytes(int value) {
        return getBytes(4, value);
    }
}

Related

1. generateKey(String secretKey)
2. generateKey(String seed)
3. generateKey(String type)
4. generateKey(String userKey, String masterKey)
5. generateKeyAES()
6. generateKeyFromString(final String secKey, String algorithm)
7. generateKeyPair()
8. generateKeyPair()
9. generateKeyPair()