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The Amazon Web Services SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2013-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.services.s3.internal.crypto;

import java.security.Provider;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;

/**
 * Factory for creating Ciphers based on the crypto key and configuration
 * specified in the constructor.
 *
 * Each invocation of {@link #createCipher()} will produce a new, identical
 * Cipher object. Each returned Cipher will encrypt data with
 * exactly the same output as any other Cipher returned by this
 * instance of CipherFactory.
 */
public class CipherFactory {
    private SecretKey symmetricKey;
    private int cipherMode;
    private byte[] initVectorBytes;
    private Provider cryptoProvider;

    /**
     * Creates a new CipherFactory that will produce ciphers using the specified
     * key, mode, IV and provider.
     *
     * @param symmetricKey
     *            The symmetric key used in the ciphers created by this factory.
     * @param cipherMode
     *            The mode indicating whether the created ciphers are for
     *            encrypting or decrypting.
     * @param initVectorBytes
     *            The optional crypto IV used to initialize the ciphers.
     * @param cryptoProvider
     *            The optional Java crypto provider implementation, if an
     *            alternate crypto provider is to be used.
     */
    public CipherFactory(SecretKey symmetricKey, int cipherMode, byte[] initVectorBytes, Provider cryptoProvider) {
        this.symmetricKey = symmetricKey;
        this.cipherMode = cipherMode;
        this.initVectorBytes = initVectorBytes;
        this.cryptoProvider = cryptoProvider;
    }

    /**
     * Creates a new Cipher instance based on the crypto parameters specified in
     * the constructor. Each Cipher instance is identical to any other Cipher
     * produced by this CipherFactory.
     *
     * @return A new Cipher instance, identical to each Cipher produced by this
     *         factory instance.
     */
    public Cipher createCipher() {
        Cipher cipher = EncryptionUtils.createSymmetricCipher(symmetricKey, cipherMode, cryptoProvider, initVectorBytes);

        // If we weren't given an IV to use, make sure we store the one the first Cipher
        // used so we can use it for all future Ciphers created by this instance.
        if (initVectorBytes == null) initVectorBytes = cipher.getIV();

        return cipher;
    }

    public Provider getCryptoProvider() {
        return cryptoProvider;
    }

    public SecretKey getSymmetricKey() {
        return symmetricKey;
    }

    public int getCipherMode() {
        return cipherMode;
    }

    public byte[] getIV() {
        return initVectorBytes == null ? null : initVectorBytes.clone();
    }
}