Encryption and Decryption in Android

CypherUtils.java

package it.bellotti.java.crypto;


import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.spec.KeySpec;

/**
 * Created with IntelliJ IDEA.
 * User: Simone Bellotti
 * Date: 05/06/2014
 * Time: 17.06
 */
public class CypherUtils {

    // Algorithm used
    private final static String ALGORITHM = "AES";


    /**
     * Encrypt data
     *
     * @param secretKey -   a secret key used for encryption
     * @param data      -   data to encrypt
     * @return Encrypted data
     * @throws Exception
     */
    private static String cipher(String secretKey, String data) throws Exception {
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), secretKey.getBytes(), 128, 256);
        SecretKey tmp = factory.generateSecret(spec);
        SecretKey key = new SecretKeySpec(tmp.getEncoded(), ALGORITHM);
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return toHex(cipher.doFinal(data.getBytes()));

    }


    /**
     * Decrypt data
     *
     * @param secretKey -   a secret key used for decryption
     * @param data      -   data to decrypt
     * @return Decrypted data
     * @throws Exception
     */
    private static String decipher(String secretKey, String data) throws Exception {
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), secretKey.getBytes(), 128, 256);
        SecretKey tmp = factory.generateSecret(spec);
        SecretKey key = new SecretKeySpec(tmp.getEncoded(), ALGORITHM);
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);
        return new String(cipher.doFinal(toByte(data)));
    }


    // Helper methods
    private static byte[] toByte(String hexString) {

        int len = hexString.length() / 2;

        byte[] result = new byte[len];

        for (int i = 0; i < len; i++) {
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
        }

        return result;

    }


    private static String toHex(byte[] stringBytes) {

        StringBuffer result = new StringBuffer(2 * stringBytes.length);
        for (int i = 0; i < stringBytes.length; i++) {
            result.append(HEX.charAt((stringBytes[i] >> 4) & 0x0f)).append(HEX.charAt(stringBytes[i] & 0x0f));
        }
        return result.toString();

    }

    public static String encrypt(String SEED, String password) {
        try {
            return cipher(SEED, password);
        } catch (Exception e) {
            Log.w("CypherUtils.encrypt", "Errore durante il cipher.", e);
            return null;
        }
    }

    public static String decrypt(String SEED, String encryptedPassword) {
        try {
            return decipher(SEED, encryptedPassword);
        } catch (Exception e) {
            Log.w("CypherUtils.decrypt", "Errore durante il decipher.", e);
            return null;
        }
    }

    private CypherUtils(){}


    private final static String HEX = "0123456789ABCDEF";
}

MainActivity.java

    protected String encrypt(String SEED, String password) {
        return CypherUtils.encrypt(SEED, password);
    }

    protected String decrypt(String SEED, String encryptedPassword) {
        return CypherUtils.decrypt(SEED, encryptedPassword);
    }