/*
 * =============================================================================
 * 
 *   Copyright (c) 2007-2010, The JASYPT team (http://www.jasypt.org)
 * 
 *   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.
 * 
 * =============================================================================
 */
package org.jasypt.salt;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import org.jasypt.exceptions.EncryptionInitializationException;

 This implementation of SaltGenerator holds a secure random 
generator which can be used for generating random salts for encryption 
or digesting.


The algorithm used for random number generation can be configured at 
instantiation time. If not, the default algorithm will be used.


This class is thread-safe.

Author:
Daniel Fernández
Since:
1.2/**
 * <p>
 * This implementation of {@link SaltGenerator} holds a <b>secure</b> random 
 * generator which can be used for generating random salts for encryption 
 * or digesting.
 * </p>
 * <p>
 * The algorithm used for random number generation can be configured at 
 * instantiation time. If not, the default algorithm will be used.
 * </p>
 * <p>
 * This class is <i>thread-safe</i>.
 * </p>
 * 
 * @since 1.2
 * 
 * @author Daniel Fern&aacute;ndez
 * 
 */
public class RandomSaltGenerator implements SaltGenerator {
    
    
The default algorithm to be used for secure random number 
generation: set to SHA1PRNG.
/**
     * The default algorithm to be used for secure random number 
     * generation: set to SHA1PRNG.
     */
    public static final String DEFAULT_SECURE_RANDOM_ALGORITHM = "SHA1PRNG";
    
    private final SecureRandom random;
    
    
    
Creates a new instance of RandomSaltGenerator using the 
default secure random number generation algorithm.
/**
     * Creates a new instance of <tt>RandomSaltGenerator</tt> using the 
     * default secure random number generation algorithm.
     */
    public RandomSaltGenerator() {
        this(DEFAULT_SECURE_RANDOM_ALGORITHM);
    }
    
    
    
Creates a new instance of RandomSaltGenerator specifying a 
secure random number generation algorithm.
Since:
1.5/**
     * Creates a new instance of <tt>RandomSaltGenerator</tt> specifying a 
     * secure random number generation algorithm.
     * 
     * @since 1.5
     * 
     */
    public RandomSaltGenerator(final String secureRandomAlgorithm) {
        super();
        try {
            this.random = SecureRandom.getInstance(secureRandomAlgorithm);
        } catch (NoSuchAlgorithmException e) {
            throw new EncryptionInitializationException(e);
        }
    }
    

    
Generate a random salt of the specified length in bytes.
Params:
lengthBytes – length in bytes.
Returns:
the generated salt./**
     * Generate a random salt of the specified length in bytes.
     * 
     * @param lengthBytes length in bytes.
     * @return the generated salt. 
     */
    public byte[] generateSalt(final int lengthBytes) {
        final byte[] salt = new byte[lengthBytes];
        synchronized (this.random) {
            this.random.nextBytes(salt);
        }
        return salt;
    }


    
This salt generator needs the salt to be included unencrypted in 
encryption results, because of its being random. This method will always 
return true.
Returns:
true/**
     * This salt generator needs the salt to be included unencrypted in 
     * encryption results, because of its being random. This method will always 
     * return true.
     * 
     * @return true
     */
    public boolean includePlainSaltInEncryptionResults() {
        return true;
    }

    
}