Crypto.java

package com.nic.epanjiyan.utils;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.*;

import javax.crypto.*;
import javax.crypto.spec.*;

import android.util.Log;
import android.util.Base64;


public class Crypto {
    private final String characterEncoding = "UTF-8";
    private final String cipherTransformation = "AES/CBC/PKCS5Padding";
    private final String aesEncryptionAlgorithm = "AES";

    public byte[] decrypt(byte[] cipherText, byte[] key, byte[] initialVector) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
        Cipher cipher = Cipher.getInstance(cipherTransformation);
        SecretKeySpec secretKeySpecy = new SecretKeySpec(key, aesEncryptionAlgorithm);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpecy, ivParameterSpec);
        cipherText = cipher.doFinal(cipherText);
        return cipherText;
    }

    public byte[] encrypt(byte[] plainText, byte[] key, byte[] initialVector) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
        Cipher cipher = Cipher.getInstance(cipherTransformation);
        SecretKeySpec secretKeySpec = new SecretKeySpec(key, aesEncryptionAlgorithm);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        plainText = cipher.doFinal(plainText);
        return plainText;
    }

    private byte[] getKeyBytes(String key) throws UnsupportedEncodingException {
        byte[] keyBytes = new byte[16];
        byte[] parameterKeyBytes = key.getBytes(characterEncoding);
        System.arraycopy(parameterKeyBytes, 0, keyBytes, 0, Math.min(parameterKeyBytes.length, keyBytes.length));
        return keyBytes;
    }

    /// <summary>
    /// Encrypts plaintext using AES 128bit key and a Chain Block Cipher and returns a base64 encoded string
    /// </summary>
    /// <param name="plainText">Plain text to encrypt</param>
    /// <param name="key">Secret key</param>
    /// <returns>Base64 encoded string</returns>
    public String encrypt(String plainText, String key) throws UnsupportedEncodingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
        byte[] plainTextbytes = plainText.getBytes(characterEncoding);
        byte[] keyBytes = getKeyBytes(key);
        return android.util.Base64.encodeToString(encrypt(plainTextbytes, keyBytes, keyBytes), Base64.DEFAULT);
    }

    /// <summary>
    /// Decrypts a base64 encoded string using the given key (AES 128bit key and a Chain Block Cipher)
    /// </summary>
    /// <param name="encryptedText">Base64 Encoded String</param>
    /// <param name="key">Secret Key</param>
    /// <returns>Decrypted String</returns>
    public String decrypt(String encryptedText, String key) throws KeyException, GeneralSecurityException, GeneralSecurityException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, IOException, UnsupportedEncodingException {
        byte[] cipheredBytes = Base64.decode(encryptedText, Base64.DEFAULT);
        byte[] keyBytes = getKeyBytes(key);
        return new String(decrypt(cipheredBytes, keyBytes, keyBytes), characterEncoding);
    }
}