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package javaapplication3;

import java.io.*;
import java.security.InvalidKeyException;
import java.security.*;

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

/**
 * A utility class that encrypts or decrypts a file.
 * @author www.codejava.net
 *
 */
public class CryptoUtils {

    public static byte[] encrypt(String ALGORITHM, String key, byte[] inputBytes)
            throws CryptoException {

        if(ALGORITHM.equals("AES") || ALGORITHM.equals("Blowfish")){
            if(key.length()>16)
                key = key.substring(0,16);
            else if(key.length()<16)
                key = key + key.substring(0, 16-key.length() );
        }
        else if(ALGORITHM.equals("DES")){
            if(key.length()>8)
                key = key.substring(0,8);
            else if(key.length()<8)
                key = key + key.substring(0, 8-key.length() );

        }

        return doCrypto(ALGORITHM, Cipher.ENCRYPT_MODE, key, inputBytes);
    }

    public static byte[] decrypt(String ALGORITHM, String key, byte[] inputBytes)
            throws CryptoException {

        if(ALGORITHM.equals("AES") || ALGORITHM.equals("Blowfish")){
            if(key.length()>16)
                key = key.substring(0,16);
            if(key.length()<16)
                key = key + key.substring(0, 16-key.length() );
        }
        else if(ALGORITHM.equals("DES")){
            if(key.length()>8)
                key = key.substring(0,8);
            else if(key.length()<8)
                key = key + key.substring(0, 8-key.length() );

        }
        return doCrypto(ALGORITHM, Cipher.DECRYPT_MODE, key, inputBytes);
    }


    public static byte[] encryptRSA(PublicKey publicKey, String message) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(message.getBytes());
    }



    public static byte[] decryptRSA(PrivateKey privateKey, byte [] encrypted) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(encrypted);
    }

    private static byte[] doCrypto(String ALGORITHM, int cipherMode, String key, byte[] inputBytes) throws CryptoException {
        try {


            Key secretKey = new SecretKeySpec(key.getBytes(), ALGORITHM);
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(cipherMode, secretKey);


            byte[] outputBytes = cipher.doFinal(inputBytes);

            return outputBytes;

        } catch (NoSuchPaddingException | NoSuchAlgorithmException
                | InvalidKeyException | BadPaddingException
                | IllegalBlockSizeException ex) {

        }


        return null;
    }

    public class CryptoException extends Exception {

    public CryptoException() {
    }

    public CryptoException(String message, Throwable throwable) {
        super(message, throwable);
    }
}
}