Main.java Source code

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Here is the source code for Main.java

Source

//package com.java2s;
/* 
 * Copyright (C) 2010 Giesecke & Devrient GmbH
 *
 * 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.
 */

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import android.util.Log;

public class Main {
    /**
     * Tag for logging
     */
    private static final String TAG = "Helper";
    /**
     * flag to indicate if the crypto-algorithms is initialized. 
     * This should only be done once, during a multi-part crypto-operation
     */
    private static boolean encryptInitialized = false;
    /**
     * Cipherobject to make encrypt operations
     */
    private static Cipher encryptCipher;

    /**
     * This method should be used to encrypt a block of data.
     * 
     * @param fileData
     *            the data to encrypt.
     * @param encryptionKey
     *            the key to initialize the cipher-algorithm.
     * @param encryptCompleted
     *            a flag, that indicates, that a multi-part encryption is to be
     *            completed. e.g. false, if the fileData consist of multiple
     *            parts. true, if the fileData consists only of one single part
     *            and so they could be encrypted in one operation.
     * 
     * @return the encrypted data.
     */
    public static byte[] encryptData(byte[] fileData, byte[] encryptionKey, boolean encryptCompleted) {

        // Initializing may only be done at the start of a multi-part crypto-operation.
        // if it's a single part crypto-operation initialization must always be done.
        if (!encryptInitialized) {
            // Initializing the cipher
            try {
                encryptCipher = Cipher.getInstance("AES");
            } catch (Exception e) {
                Log.e(TAG, "Error while initializing encryption.");
                return null;
            }

            try {
                SecretKeySpec keySpec = new SecretKeySpec(encryptionKey, "AES");
                encryptCipher.init(Cipher.ENCRYPT_MODE, keySpec);
            } catch (Exception e) {
                Log.e(TAG, "Error while initializing encryption.");
                return null;
            }
            encryptInitialized = true;
        }

        // encrypting
        try {
            if (!encryptCompleted)
                // done in case of multi-part operation
                fileData = encryptCipher.update(fileData);
            else
                // done in case of single part operation or to finish a multi-part operation
                fileData = encryptCipher.doFinal(fileData);
        } catch (Exception e) {
            Log.e(TAG, "Error during encryption.");
            return null;
        }

        // at the and of an multi-part operation flags must be reset
        if (encryptCompleted)
            encryptInitialized = false;
        return fileData;
    }
}