Crypto.java

package org.cnodejs.android.md.util;

import android.support.annotation.NonNull;

import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public final class Crypto {

    public static final Crypto AES = new Crypto("AES", 16, 16);

    private final String algorithm;
    private final int secretLength;
    private final int ivLength;

    private Crypto(@NonNull String algorithm, int secretLength, int ivLength) {
        this.algorithm = algorithm;
        this.secretLength = secretLength;
        this.ivLength = ivLength;
    }

    public SecretKey generateSecret(@NonNull byte[] seed) {
        return new SecretKeySpec(Arrays.copyOf(seed, secretLength), algorithm);
    }

    public IvParameterSpec generateIv(@NonNull byte[] seed) {
        return new IvParameterSpec(Arrays.copyOf(seed, ivLength));
    }

    public byte[] encrypt(@NonNull SecretKey secret, @NonNull IvParameterSpec iv, @NonNull byte[] data) throws CryptoException {
        try {
            Cipher cipher = Cipher.getInstance(algorithm + "/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, secret, iv);
            return cipher.doFinal(data);
        } catch (NoSuchAlgorithmException | InvalidKeyException | InvalidAlgorithmParameterException | NoSuchPaddingException | BadPaddingException | IllegalBlockSizeException e) {
            throw new CryptoException("Encrypt error.", e);
        }
    }

    public byte[] decrypt(@NonNull SecretKey secret, @NonNull IvParameterSpec iv, @NonNull byte[] data) throws CryptoException {
        try {
            Cipher cipher = Cipher.getInstance(algorithm + "/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, secret, iv);
            return cipher.doFinal(data);
        } catch (NoSuchAlgorithmException | InvalidKeyException | InvalidAlgorithmParameterException | NoSuchPaddingException | BadPaddingException | IllegalBlockSizeException e) {
            throw new CryptoException("Decrypt error.", e);
        }
    }

    public static class CryptoException extends Exception {

        private CryptoException(String message, Throwable cause) {
            super(message, cause);
        }

    }

}