/*
 * =============================================================================
 * 
 *   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.util.digest;

import java.security.Provider;

import org.jasypt.digest.StandardByteDigester;

 Utility class for creating digests without using a salt or iterating the hash function. This means that digests created by this class will be compatible (and equivalent) to the ones which could be created by the user by directly using a MessageDigest object. 
 This class can be thought of as convenience wrapper for MessageDigest, adding thread-safety and a more javabean-like interface to it. These two features enable a more adequate use from an IoC container like Spring. 
 This class internally holds a StandardByteDigester configured this way: 

  
Algorithm: MD5 by default, but configurable.
  
Provider: Default JVM security provider, but configurable.
 
  
Salt size: 0 bytes, no salt used.
  
Iterations: 1, hash function will not be iterated.



This class is thread-safe

Author:
Daniel Fernández
Since:
1.2 (class existed as org.jasypt.util.MessageDigester since 1.1)/**
 * <p>
 * Utility class for creating digests without using a salt or iterating
 * the hash function. This means that digests created by this class will
 * be compatible (and equivalent) to the ones which could be created by 
 * the user by directly using a {@link java.security.MessageDigest} object.
 * </p>
 * <p>
 * This class can be thought of as convenience wrapper for 
 * {@link java.security.MessageDigest}, adding thread-safety and
 * a more javabean-like interface to it. These two features enable a more
 * adequate use from an IoC container like Spring. 
 * </p>
 * <p>
 * This class internally holds a {@link StandardByteDigester} 
 * configured this way:
 * <ul>
 *   <li>Algorithm: <tt>MD5</tt> by default, but configurable.</li>
 *   <li>Provider: Default JVM security provider, but configurable.</li> 
 *   <li>Salt size: <tt>0 bytes</tt>, no salt used.</li>
 *   <li>Iterations: <tt>1</tt>, hash function will not be iterated.</li>
 * </ul>
 * </p>
 * <p>
 * This class is <i>thread-safe</i>
 * </p>
 * 
 * @since 1.2 (class existed as org.jasypt.util.MessageDigester since 1.1)
 * 
 * @author Daniel Fern&aacute;ndez
 * 
 */
public final class Digester {

    
    
MD5 will be the default algorithm to be used if none is specified.
/**
     * MD5 will be the default algorithm to be used if none is specified.
     */
    public static final String DEFAULT_ALGORITHM = "MD5";

    // The hash function will be applied only once
    private static final int ITERATIONS = 1;
    
    // No salt will be used
    private static final int SALT_SIZE_BYTES = 0;
    
    // The internal digester used
    private final StandardByteDigester digester;
    
    
    
Creates a new instance of Digester. It will use the default algorithm unless one is specified with setAlgorithm(String). /**
     * Creates a new instance of <tt>Digester</tt>. It will use
     * the default algorithm unless one is specified with 
     * {@link #setAlgorithm(String)}. 
     *
     */
    public Digester() {
        super();
        this.digester = new StandardByteDigester();
        this.digester.setIterations(ITERATIONS);
        this.digester.setSaltSizeBytes(SALT_SIZE_BYTES);
    }
    
    

Creates a new instance of Digester, specifying
the algorithm to be used.

/**
     * <p>
     * Creates a new instance of <tt>Digester</tt>, specifying
     * the algorithm to be used.
     * </p>
     */
    public Digester(final String algorithm) {
        super();
        this.digester = new StandardByteDigester();
        this.digester.setIterations(ITERATIONS);
        this.digester.setSaltSizeBytes(SALT_SIZE_BYTES);
        this.digester.setAlgorithm(algorithm);
    }

    
    

Creates a new instance of Digester, specifying
the algorithm to be used.

Since:
1.3/**
     * <p>
     * Creates a new instance of <tt>Digester</tt>, specifying
     * the algorithm to be used.
     * </p>
     * 
     * @since 1.3
     */
    public Digester(final String algorithm, final String providerName) {
        super();
        this.digester = new StandardByteDigester();
        this.digester.setIterations(ITERATIONS);
        this.digester.setSaltSizeBytes(SALT_SIZE_BYTES);
        this.digester.setAlgorithm(algorithm);
        this.digester.setProviderName(providerName);
    }

    
    

Creates a new instance of Digester, specifying
the algorithm to be used.

Since:
1.3/**
     * <p>
     * Creates a new instance of <tt>Digester</tt>, specifying
     * the algorithm to be used.
     * </p>
     * 
     * @since 1.3
     */
    public Digester(final String algorithm, final Provider provider) {
        super();
        this.digester = new StandardByteDigester();
        this.digester.setIterations(ITERATIONS);
        this.digester.setSaltSizeBytes(SALT_SIZE_BYTES);
        this.digester.setAlgorithm(algorithm);
        this.digester.setProvider(provider);
    }
    
    
    

Sets the algorithm to be used for digesting, like MD5 
or SHA-1.


This algorithm has to be supported by your security infrastructure, and
it should be allowed as an algorithm for creating
java.security.MessageDigest instances.

 If you are specifying a security provider with setProvider(Provider) or setProviderName(String), this algorithm should be supported by your specified provider. 

If you are not specifying a provider, you will be able to use those
algorithms provided by the default security provider of your JVM vendor.
For valid names in the Sun JVM, see Java 
        Cryptography Architecture API Specification & 
        Reference.

Params:
algorithm – the name of the algorithm to be used.
Throws:
AlreadyInitializedException – if it has already been initialized, this is, if digest(byte[]) has been called at least once./**
     * <p>
     * Sets the algorithm to be used for digesting, like <tt>MD5</tt> 
     * or <tt>SHA-1</tt>.
     * </p>
     * <p>
     * This algorithm has to be supported by your security infrastructure, and
     * it should be allowed as an algorithm for creating
     * java.security.MessageDigest instances.
     * </p>
     * <p>
     * If you are specifying a security provider with {@link #setProvider(Provider)} or
     * {@link #setProviderName(String)}, this algorithm should be
     * supported by your specified provider.
     * </p>
     * <p>
     * If you are not specifying a provider, you will be able to use those
     * algorithms provided by the default security provider of your JVM vendor.
     * For valid names in the Sun JVM, see <a target="_blank" 
     *         href="http://java.sun.com/j2se/1.5.0/docs/guide/security/CryptoSpec.html#AppA">Java 
     *         Cryptography Architecture API Specification & 
     *         Reference</a>.
     * </p>
     * 
     * @param algorithm the name of the algorithm to be used.
     * @throws AlreadyInitializedException if it has already been initialized,
     *         this is, if {@link #digest(byte[])} has been called at least
     *         once.
     */
    public void setAlgorithm(final String algorithm) {
        this.digester.setAlgorithm(algorithm);
    }

    
    

Sets the name of the security provider to be asked for the
digest algorithm. This security provider has to be registered beforehand
at the JVM security framework. 

 The provider can also be set with the setProvider(Provider) method, in which case it will not be necessary neither registering the provider beforehand, nor calling this setProviderName(String) method to specify a provider name. 
 Note that a call to setProvider(Provider) overrides any value set by this method. 

If no provider name / provider is explicitly set, the default JVM
provider will be used.

Params:
providerName – the name of the security provider to be asked
                    for the digest algorithm.
Throws:
AlreadyInitializedException – if it has already been initialized, this is, if digest(byte[]) has been called at least once.
Since:
1.3/**
     * <p>
     * Sets the name of the security provider to be asked for the
     * digest algorithm. This security provider has to be registered beforehand
     * at the JVM security framework. 
     * </p>
     * <p>
     * The provider can also be set with the {@link #setProvider(Provider)}
     * method, in which case it will not be necessary neither registering
     * the provider beforehand,
     * nor calling this {@link #setProviderName(String)} method to specify
     * a provider name.
     * </p>
     * <p>
     * Note that a call to {@link #setProvider(Provider)} overrides any value 
     * set by this method.
     * </p>
     * <p>
     * If no provider name / provider is explicitly set, the default JVM
     * provider will be used.
     * </p>
     * 
     * @since 1.3
     * 
     * @param providerName the name of the security provider to be asked
     *                     for the digest algorithm.
     * @throws AlreadyInitializedException if it has already been initialized,
     *         this is, if {@link #digest(byte[])} has been called at least
     *         once.
     */
    public void setProviderName(final String providerName) {
        this.digester.setProviderName(providerName);
    }
    
    
    

Sets the security provider to be asked for the digest algorithm.
The provider does not have to be registered at the security 
infrastructure beforehand, and its being used here will not result in
it being registered.

 If this method is called, calling setProviderName(String) becomes unnecessary. 

If no provider name / provider is explicitly set, the default JVM
provider will be used.

Params:
provider – the provider to be asked for the chosen algorithm
Throws:
AlreadyInitializedException – if it has already been initialized, this is, if digest(byte[]) has been called at least once.
Since:
1.3/**
     * <p>
     * Sets the security provider to be asked for the digest algorithm.
     * The provider does not have to be registered at the security 
     * infrastructure beforehand, and its being used here will not result in
     * it being registered.
     * </p>
     * <p>
     * If this method is called, calling {@link #setProviderName(String)}
     * becomes unnecessary.
     * </p>
     * <p>
     * If no provider name / provider is explicitly set, the default JVM
     * provider will be used.
     * </p>
     * 
     * @since 1.3
     * 
     * @param provider the provider to be asked for the chosen algorithm
     * @throws AlreadyInitializedException if it has already been initialized,
     *         this is, if {@link #digest(byte[])} has been called at least
     *         once.
     */
    public void setProvider(final Provider provider) {
        this.digester.setProvider(provider);
    }

    
    
Creates a digest.
Params:
binary – the byte array to be digested.
See Also:
StandardByteDigester.digest(byte[])
Returns:
the resulting digest./**
     * Creates a digest.
     * 
     * @param binary the byte array to be digested.
     * @return the resulting digest.
     * @see StandardByteDigester#digest(byte[])
     */
    public byte[] digest(final byte[] binary) {
        return this.digester.digest(binary);
    }

    
}