EncryptionUtils.java

/**
 * This is a utility class that gives convenience methods for cryptography
 * I actually wrote this class to help out a friend @clyne
 * 
 * @author Samuel Male
 */
public class EncrptionUtils {
	
	/**
	 * It does the Encryption. It actually delegates {@link #encrypt(String, String, Operation)} internally.
	 * @param key
	 * @param value
	 * @return
	 */
	public static String doEncrypt(String key, String value) {
		byte [] cipher = encrypt(key, value, Operation.ENCRYPT);
		return new String(cipher);
	}
	/**
	 * It does the Decryption. It actually delegates {@link #encrypt(String, String, Operation)} internally.
	 * @param key to use to do decryption
	 * @param value encrypted value to decrypt
	 * @return the actual value
	 */
	public static String doDecrypt(String key, String value) {
		// Convert the bytes to the right cipher(integers separated by commas)
		String cipher = new String(value.getBytes());
		byte [] decryptedValue = encrypt(key, cipher, Operation.DECRYPT);
		return new String(decryptedValue);	
	}
	
	/**
	 * It does both <code>Encryption</code> and <code>Decryption</code>
	 * Well with this implementation, we don't need the <a href="https://en.wikipedia.org/wiki/One-time_pad">One Time Pad</a> method.
	 * For details why see : https://stackoverflow.com/questions/42923469/one-time-pad-xor-cipher
	 * Encryption is done by <code>XOR<code>ing the key with the value and then encode the result to bits
	 * @param key the key used for both operations
	 * @param value value of either the cipher(encrypted value to decrypt) or value to encrypted
	 * @param operation the {@link Operation} either Decryption or Encryption
	 * @return byte array of either the cipher or decryption
	 * 
	 */
	public static byte[] encrypt(String key, String value, Operation operation) {
		char [] keyChars = key.toCharArray(); 
		char [] valueChars = value.toCharArray();

		StringBuilder cipherBuilder = new StringBuilder();
		// If we are decrypting, lets generate write array of characters of the cipher
		if (operation.equals(Operation.DECRYPT)) {
			// Give it a new reference
			cipherBuilder = new StringBuilder();
			// convert the decimals to the corresponding characters
			String[] rawCharacters = value.split(",");
			for (int i = 0; i < rawCharacters.length; i++) {
				int rawChar = Integer.valueOf(rawCharacters[i]);
				char cipherChar = (char) rawChar;
				cipherBuilder.append(cipherChar);
			}
			valueChars = cipherBuilder.toString().toCharArray();
			// Drop the cache
			cipherBuilder = new StringBuilder(); 
		}
		for (int i = 0; i < valueChars.length; i++) {
			// Because some unicodes aren't visually printed on the screen eg. '\0'
			// We gonna create a cipher of ints separated by commas to have a full visible cipher
			int intForCharacter = (valueChars[i] ^ keyChars[i]);
			// if we are encrypting, we need to generate the cipher in away that it contains the
			// raw integers for the containing characters which will turned to bits
			if (operation.equals(Operation.ENCRYPT)) {
				// Check whether it's not the last index
				if (i != valueChars.length - 1) {
					cipherBuilder.append(intForCharacter + ",");
				} else {
					// Don't append the ','
					cipherBuilder.append(intForCharacter);
				}
			} else {
				cipherBuilder.append((char)intForCharacter);
			}
		}
		if (operation.equals(Operation.ENCRYPT)) {
			return cipherBuilder.toString().getBytes();
		}
		return cipherBuilder.toString().getBytes();
	}
	
	public enum Operation {
		ENCRYPT, DECRYPT
	}
	
	// Test out the program
	public static void main(String[] args) {
		// First of all let's encrypt
		String key = "oko2$_", password = "$clyne";
		String cipher = doEncrypt(key, password);
		// Log the encrypted string
		System.out.println("Cipher : " + cipher);
		// Decrypt
		String clynezPassword = doDecrypt(key, cipher);
		// Log the password
		System.out.println("Password : " + clynezPassword);
	}
	
	//TODO : I'm pretty tired now but the key should randomly generated
	//TODO : Improve #doEncrypt() slightly to return a string of bits instead of the ugly figures
	//LUCK
}