de.alpharogroup.crypto.simple.SimpleDecryptor.java Source code

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Here is the source code for de.alpharogroup.crypto.simple.SimpleDecryptor.java

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/**
 * Copyright (C) 2007 Asterios Raptis
 *
 * 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 de.alpharogroup.crypto.simple;

import java.io.UnsupportedEncodingException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

import lombok.AccessLevel;
import lombok.Getter;

import org.apache.commons.codec.binary.Base64;

import de.alpharogroup.check.Check;
import de.alpharogroup.crypto.CryptConst;
import de.alpharogroup.crypto.interfaces.Decryptor;

/**
 * A simple Decryptor implementation.
 *
 * @author Asterios Raptis
 * @version 1.0
 */
public class SimpleDecryptor implements Decryptor {

    /**
     * The Cipher object.
     */
    private Cipher cipher;

    /**
     * The private key.
     */
    @Getter
    private final String privateKey;

    /**
     * The flag initialized that indicates if the cypher is initialized for decryption.
     *
     * @return true, if is initialized
     */
    @Getter(value = AccessLevel.PRIVATE)
    private boolean initialized;

    /**
     * Constructor with a private key.
     *
     * @param privateKey
     *            The private key.
     */
    public SimpleDecryptor(final String privateKey) {
        Check.get().notEmpty(privateKey, "privateKey");
        this.privateKey = privateKey;
    }

    /**
     * Decrpyt the given encrypted String.
     * 
     * @param encypted
     *            The String to decrypt.
     * @throws BadPaddingException
     *             is thrown if {@link Cipher#doFinal(byte[])} fails.
     * @throws IllegalBlockSizeException
     *             is thrown if {@link Cipher#doFinal(byte[])} fails.
     * @throws UnsupportedEncodingException
     *             is thrown if creation of String object fails.
     * @throws InvalidAlgorithmParameterException
     *             is thrown if initialization of the cypher object fails.
     * @throws NoSuchPaddingException
     *             is thrown if instantiation of the cypher object fails.
     * @throws InvalidKeySpecException
     *             is thrown if generation of the SecretKey object fails.
     * @throws NoSuchAlgorithmException
     *             is thrown if instantiation of the SecretKeyFactory object fails.
     * @throws InvalidKeyException
     *             is thrown if initialization of the cypher object fails.
     *
     * @see de.alpharogroup.crypto.interfaces.Decryptor#decrypt(java.lang.String)
     */
    @Override
    public String decrypt(final String encypted) throws IllegalBlockSizeException, BadPaddingException,
            UnsupportedEncodingException, InvalidKeyException, NoSuchAlgorithmException, InvalidKeySpecException,
            NoSuchPaddingException, InvalidAlgorithmParameterException {
        initialize();
        final byte[] dec = Base64.decodeBase64(encypted);
        final byte[] utf8 = this.cipher.doFinal(dec);
        return new String(utf8, CryptConst.ENCODING);
    }

    /**
     * Initializes the {@link SimpleDecryptor} object.
     *
     * @throws InvalidAlgorithmParameterException
     *             is thrown if initialization of the cypher object fails.
     * @throws NoSuchPaddingException
     *             is thrown if instantiation of the cypher object fails.
     * @throws InvalidKeySpecException
     *             is thrown if generation of the SecretKey object fails.
     * @throws NoSuchAlgorithmException
     *             is thrown if instantiation of the SecretKeyFactory object fails.
     * @throws InvalidKeyException
     *             is thrown if initialization of the cypher object fails.
     */
    private void initialize() throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException,
            InvalidKeyException, InvalidAlgorithmParameterException {
        if (!isInitialized()) {
            KeySpec keySpec = null;
            if (this.getPrivateKey() != null) {
                keySpec = new PBEKeySpec(this.getPrivateKey().toCharArray());
            }
            if (this.getPrivateKey() == null) {
                keySpec = new PBEKeySpec(CryptConst.PRIVATE_KEY.toCharArray());
            }
            final SecretKeyFactory factory = SecretKeyFactory.getInstance(CryptConst.PBEWITH_MD5AND_DES);
            final SecretKey key = factory.generateSecret(keySpec);
            this.cipher = Cipher.getInstance(key.getAlgorithm());
            final AlgorithmParameterSpec paramSpec = new PBEParameterSpec(CryptConst.SALT,
                    CryptConst.ITERATIONCOUNT);
            this.cipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
            initialized = true;
        }
    }
}