co.rsk.crypto.KeyCrypterAes.java Source code

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Here is the source code for co.rsk.crypto.KeyCrypterAes.java

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/*
 * This file is part of RskJ
 * Copyright (C) 2017 RSK Labs Ltd.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Copyright 2013 Jim Burton.
 * Copyright 2014 Andreas Schildbach
 *
 * Licensed under the MIT license (the "License")
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://opensource.org/licenses/mit-license.php
 *
 * 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 co.rsk.crypto;

import org.bouncycastle.crypto.BufferedBlockCipher;
import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

import java.security.SecureRandom;
import java.util.Arrays;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * This class encrypts and decrypts byte arrays using AES symmetric cipher.
 */
public class KeyCrypterAes implements KeyCrypter {

    /**
     * The size of an AES block in bytes.
     * This is also the length of the initialisation vector.
     */
    private static final int BLOCK_LENGTH = 16; // = 128 bits.

    private static final SecureRandom secureRandom = new SecureRandom();

    /**
     * Password based encryption using AES - CBC 256 bits.
     */
    @Override
    public EncryptedData encrypt(byte[] plainBytes, KeyParameter key) {
        checkNotNull(plainBytes);
        checkNotNull(key);

        try {
            // Generate iv - each encryption call has a different iv.
            byte[] iv = new byte[BLOCK_LENGTH];
            secureRandom.nextBytes(iv);

            ParametersWithIV keyWithIv = new ParametersWithIV(key, iv);

            // Encrypt using AES.
            BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()));
            cipher.init(true, keyWithIv);
            byte[] encryptedBytes = new byte[cipher.getOutputSize(plainBytes.length)];
            final int length1 = cipher.processBytes(plainBytes, 0, plainBytes.length, encryptedBytes, 0);
            final int length2 = cipher.doFinal(encryptedBytes, length1);

            return new EncryptedData(iv, Arrays.copyOf(encryptedBytes, length1 + length2));
        } catch (Exception e) {
            throw new KeyCrypterException("Could not encrypt bytes.", e);
        }
    }

    /**
     * Decrypt bytes previously encrypted with this class.
     *
     * @param dataToDecrypt    The data to decrypt
     * @param key              The AES key to use for decryption
     * @return                 The decrypted bytes
     * @throws                 KeyCrypterException if bytes could not be decrypted
     */
    @Override
    public byte[] decrypt(EncryptedData dataToDecrypt, KeyParameter key) {
        checkNotNull(dataToDecrypt);
        checkNotNull(key);

        try {
            ParametersWithIV keyWithIv = new ParametersWithIV(new KeyParameter(key.getKey()),
                    dataToDecrypt.initialisationVector);

            // Decrypt the message.
            BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()));
            cipher.init(false, keyWithIv);

            byte[] cipherBytes = dataToDecrypt.encryptedBytes;
            byte[] decryptedBytes = new byte[cipher.getOutputSize(cipherBytes.length)];
            final int length1 = cipher.processBytes(cipherBytes, 0, cipherBytes.length, decryptedBytes, 0);
            final int length2 = cipher.doFinal(decryptedBytes, length1);

            return Arrays.copyOf(decryptedBytes, length1 + length2);
        } catch (Exception e) {
            throw new KeyCrypterException("Could not decrypt bytes", e);
        }
    }
}