The code for a (basic) encryption approach is attached and should be completed to show how Strings are encrypted and decrypted. The code also showcases how easy it is to (sneakily) intercept code and store information (in this case, by the original programmer). Add a component to your code that saves the developed SimpleEnigma object to a file.

JAVA CODE:

//Crypto.java

public interface Crypto {

/**

* @param unencryptedString The raw string to be encryped.

* @return The encrypted string.

*/

public String encrypt(String unencryptedString);

/**

* @param encryptedString An encrypted string.

* @return A decrypted string.

*/

public String decrypt(String encryptedString);

}

//CyptoError.java

/**

* A custom error class example.

*

*

*/

public class CryptoError extends Exception {

private static final long serialVersionUID = 1L;

public CryptoError(String message) {

super(message);

}

}

//Main.java

public class Main {

/**

* @param args (not used)

*/

public static void main(String[] args) {

SimpleEnigma enigma = new SimpleEnigma();

String enc = enigma.encrypt("Demo Text");

System.out.println("Secret message : " + enc);

String dec = enigma.decrypt(enc);

System.out.println("Decoded message: " + dec);

System.out.println("Not-so secret messages:");

System.out.println(enigma);

}

}

//SimpleEnigma.java

import java.io.Serializable;

import java.util.ArrayList;

public class SimpleEnigma implements Crypto, Serializable {

private static final long serialVersionUID = 1L;

private ArrayList backDoorMessages;

public SimpleEnigma() {

backDoorMessages = new ArrayList();

}

/**

* @param unencrypted

* @return

* @throws CryptoError

*/

private char crypted(char unencrypted) throws CryptoError {

if ((unencrypted - 10) < 18)

throw new CryptoError("Incoming char ASCII code must be >= 28!");

return (char) (unencrypted - 10);

}

/**

* @param encrypted

* @return

* @throws CryptoError

*/

private char decrypted(char encrypted) throws CryptoError {

if ((encrypted + 10) < 28)

throw new CryptoError("Ambiguous incoming ASCII code.");

return (char) (encrypted + 10);

}

/**

* @param unencryptedString

* @return

* @throws CryptoError

*/

@Override

public String encrypt(String unencryptedString) {

String encodedString = "";

try {

for (int i = 0; i < unencryptedString.length(); i++) {

encodedString += crypted(unencryptedString.charAt(i));

}

} catch (CryptoError e) {

e.printStackTrace();

} finally {

backDoorMessages.add(unencryptedString);

}

return encodedString;

}

/**

* @param unencryptedString

* @return

* @throws CryptoError

*/

@Override

public String decrypt(String encryptedString) {

// TODO You fill in the blanks

return null;

}

@Override

public String toString() {

String retString = "";

for (String mesg : backDoorMessages)

retString += mesg + " ";

return retString;

}

}