Encrypt and Decrypt in Java

Issue

I would like to store an encrypted password in a Java file. I saw at a solution using javax.crypto, but the problem with that was that the key was being generated on the fly and it was random.

This password will be then taken and decrypted in the Java program in runtime. Given that I am going to store an already encrypted password in a file - I want to get the right text when decrypting it.

Is there a way to tell the javax.crypto method:

key = KeyGenerator.getInstance(algorithm).generateKey()

Can this be replaced with my own key generated once based on some private key?

Can anyone point me to some resources on how to do this?

Solution

Here is a solution using the javax.crypto library and the apache commons codec library for encoding and decoding in Base64 that I was looking for:

import java.security.spec.KeySpec;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESedeKeySpec;
import org.apache.commons.codec.binary.Base64;

public class TrippleDes {

    private static final String UNICODE_FORMAT = "UTF8";
    public static final String DESEDE_ENCRYPTION_SCHEME = "DESede";
    private KeySpec ks;
    private SecretKeyFactory skf;
    private Cipher cipher;
    byte[] arrayBytes;
    private String myEncryptionKey;
    private String myEncryptionScheme;
    SecretKey key;

    public TrippleDes() throws Exception {
        myEncryptionKey = "ThisIsSpartaThisIsSparta";
        myEncryptionScheme = DESEDE_ENCRYPTION_SCHEME;
        arrayBytes = myEncryptionKey.getBytes(UNICODE_FORMAT);
        ks = new DESedeKeySpec(arrayBytes);
        skf = SecretKeyFactory.getInstance(myEncryptionScheme);
        cipher = Cipher.getInstance(myEncryptionScheme);
        key = skf.generateSecret(ks);
    }


    public String encrypt(String unencryptedString) {
        String encryptedString = null;
        try {
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] plainText = unencryptedString.getBytes(UNICODE_FORMAT);
            byte[] encryptedText = cipher.doFinal(plainText);
            encryptedString = new String(Base64.encodeBase64(encryptedText));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return encryptedString;
    }


    public String decrypt(String encryptedString) {
        String decryptedText=null;
        try {
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] encryptedText = Base64.decodeBase64(encryptedString);
            byte[] plainText = cipher.doFinal(encryptedText);
            decryptedText= new String(plainText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return decryptedText;
    }


    public static void main(String args []) throws Exception
    {
        TrippleDes td= new TrippleDes();

        String target="imparator";
        String encrypted=td.encrypt(target);
        String decrypted=td.decrypt(encrypted);

        System.out.println("String To Encrypt: "+ target);
        System.out.println("Encrypted String:" + encrypted);
        System.out.println("Decrypted String:" + decrypted);

    }

}

Running the above program results with the following output:

String To Encrypt: imparator
Encrypted String:FdBNaYWfjpWN9eYghMpbRA==
Decrypted String:imparator

Answered By - oneiros