OneWayEncryptionService.java

/*
 * OneWayEncryptionService.java
 *
 * Created on Apr 21, 2009, 2:57:10 PM
 *
 * Description: Provides a singleton one-way encryption service.
 *
 * Copyright (C) Apr 21, 2009 Stephen L. Reed.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program;
 * if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.texai.util;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import net.jcip.annotations.ThreadSafe;

/**  Provides a singleton one-way encryption service.  Adapted from James Shvarts' article "Password Encryption: Rationale and Java Example"
 * http://www.devarticles.com/c/a/Java/Password-Encryption-Rationale-and-Java-Example
 *
 * The Sun BASE64Encoder class has been replaced with an open source equivalent.
 *
 * @author Stephen L. Reed
 */
@ThreadSafe
public final class OneWayEncryptionService {

  /** the singleton one-way encryption service */
  private static OneWayEncryptionService instance;

  /** Privately constructs a new one-way encryption service instance. */
  private OneWayEncryptionService() {
  }

  /** Encrypts the given plaintext and returns the encrypted text.
   *
   * @param plaintext the plaintext
   * @return the encrypted text
   */
  public synchronized String encrypt(final String plaintext) {
    //Preconditions
    assert plaintext != null : "plaintext must not be null";
    assert !plaintext.isEmpty() : "plaintext must not be empty";

    MessageDigest messageDigest = null;
    try {
      messageDigest = MessageDigest.getInstance("SHA");
    } catch (NoSuchAlgorithmException e) {
      throw new TexaiException(e);
    }
    try {
      messageDigest.update(plaintext.getBytes("UTF-8"));
    } catch (UnsupportedEncodingException ex) {
      throw new TexaiException(ex);
    }
    final byte[] raw = messageDigest.digest();
    return new String(Base64Coder.encode(raw));
  }

  /** Encrypts the bytes that constitute the given number and returns the encrypted text.
   *
   * @param nbr the number to be encrypted
   * @return the encrypted text
   */
  public synchronized String encrypt(final long nbr) {
    final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    final DataOutputStream dataOutputStream = new DataOutputStream(byteArrayOutputStream);
    try {
    dataOutputStream.writeLong(nbr);
    dataOutputStream.flush();
    } catch (final IOException ex) {
      throw new TexaiException(ex);
    }
    MessageDigest messageDigest = null;
    try {
      messageDigest = MessageDigest.getInstance("SHA");
    } catch (NoSuchAlgorithmException e) {
      throw new TexaiException(e);
    }
    messageDigest.update(byteArrayOutputStream.toByteArray());
    final byte[] raw = messageDigest.digest();
    return new String(Base64Coder.encode(raw));
  }

  /** Gets the singleton one-way encryption service.
   *
   * @return the singleton one-way encryption service
   */
  public static synchronized OneWayEncryptionService getInstance() {
    if (instance == null) {
      return new OneWayEncryptionService();
    } else {
      return instance;
    }
  }
}