fixed final bugs

Crypto-CS107-2020/src/crypto/Decrypt.java

@@ -24,16 +24,9 @@ public class Decrypt {
 	 * @return the decoded string or the original encoded message if type is not in the list above.
 	 */
 	public static String breakCipher(String cipher, int type) {
-		//The method should be such that if you call it with cipher and type, it will decrypt the message
 
 		byte[] plainText = stringToBytes(cipher);
-		String output = null;
-
-		byte[] keywordInverse = new byte[vigenereWithFrequencies(plainText).length]; //Calculates the inverse keyword for Vigenere
-
-		for (int i = 0; i < (vigenereWithFrequencies(plainText).length); ++i) {
-			keywordInverse[i] = (byte) (-(vigenereWithFrequencies(plainText)[i]));
-		}
+		String output = "";
 
 		while ((type < 0) || (type > 2))
 			System.out.println("False input. Please enter a type that is within the range of 0-2: 0 = Caesar; 1 = Vigenere; 2 = XOR");
@@ -42,7 +35,7 @@ public static String breakCipher(String cipher, int type) {
 			output = bytesToString(Encrypt.caesar(plainText, (byte) (-(caesarWithFrequencies(plainText)))));
 
 		else if (type == Encrypt.VIGENERE) //VIGENERE = 1
-			output = bytesToString(Encrypt.vigenere(plainText, keywordInverse));
+			output = bytesToString(vigenereWithFrequencies(plainText));
 
 		else if (type == Encrypt.XOR) //XOR = 2
 			output = arrayToString(xorBruteForce(plainText));
@@ -220,20 +213,34 @@ public static byte[][] xorBruteForce(byte[] cipher) {
 	 * @return the byte encoding of the clear text
 	 */
 	public static byte[] vigenereWithFrequencies(byte[] cipher) {
+		assert (cipher.length >= 6);
 		/* Method used:
 		 * 	1. Create an iterator from 0 to 255 (inclusive => 256 values) /
 		 * 	2. Multiply ENGLISHFREQUENCIES with A*0 (It. 0), A*1 (It. 1), ..., A*255 (It. 255) /
 		 *  3. Create a wrap-around so if the charFreqIndex goes above 255, it wraps back to 0 /
 		 *  4. Find the index of the biggest scalar product out of all scalar products => Error here: always returns 255
 		 *  Distance between charFrequencies[i] and 97 is the key
 		 */
+
+		if (cipher.length <= 1) {
+			//Fixes error where a cipher with length 1 causes error:
+			System.out.println("The inputted text is too small, please use a larger sized cipher");
+			byte[] empty = {};
+			return empty;
+		}
 
 		List<Byte> cleanCipher = removeSpaces(cipher);
-		int keyLength = vigenereFindKeyLength(cleanCipher);
 
-		byte[] vigenereKey = Decrypt.vigenereFindKey(cleanCipher, keyLength);
-
-		return vigenereKey;
+		byte[] vigenereKey = Decrypt.vigenereFindKey(cleanCipher, vigenereFindKeyLength(cleanCipher)); //Returns vigenere-encoding key
+		byte[] keywordInverse = new byte[vigenereKey.length]; //Calculates the inverse keyword for Vigenere
+
+		for (int i = 0; i < vigenereKey.length; ++i) {
+			keywordInverse[i] = (byte)(-vigenereKey[i]);
+		}
+
+		byte[] decryptedCipher = Encrypt.vigenere(cipher, keywordInverse);
+
+		return decryptedCipher;
 	}
 
 
@@ -296,6 +303,7 @@ public static int vigenereFindKeyLength(List<Byte> cipher) {
 	 * @return the inverse key to decode the Vigenere cipher text
 	 */
 	public static byte[] vigenereFindKey(List<Byte> cipher, int keyLength) {
+		assert (cipher.size() >= 6);
 		/* Method used:
 		 * Recover the key values:
 		 *      -> Divide the cipher by keyLength, into keyLength strings
@@ -393,6 +401,7 @@ public static int[]	calculateCoincidences (List<Byte> cipher) {
 	 * @return the Integer dynamic array containing the indices of all the localMaximas (in ascending index order)
 	 */
 	public static List<Integer> calculateMaximas(List<Byte> cipher, int[] coincidences){
+
 		int maxIndex = (int)Math.ceil(cipher.size()/2); //If cipher.size/2 = 7.5 => Math.ciel returns 8
 		List<Integer> localMaximas = new ArrayList<Integer>(); //stores the indices of local Maximas
 

Crypto-CS107-2020/src/crypto/Encrypt.java

@@ -28,7 +28,7 @@ public class Encrypt {
 	 */
 	public static String encrypt(String message, String key, int type) {
 
-		String output = null;
+		String output = "";
 
 		byte[] plainText = Helper.stringToBytes(message);
 		assert (plainText != null);
@@ -48,7 +48,12 @@ public static String encrypt(String message, String key, int type) {
 			output = bytesToString(xor(plainText, keyByte));
 			// By default, space encoding is OFF for XOR
 		} else if (type == ONETIME) { //ONETIME = 3
-			output = bytesToString(oneTimePad(plainText, keyBytes));
+			if (oneTimePad(plainText, keyBytes) != plainText) {
+				output = bytesToString(oneTimePad(plainText, keyBytes));
+			}
+			else {
+				output = "";
+			}
 			// By default, space encoding is ON for Onetimepad
 		} else if (type == CBC) { //CBC = 4
 			output = bytesToString(cbc(plainText, keyBytes));
@@ -202,8 +207,9 @@ public static byte[] oneTimePad(byte[] plainText, byte[] pad) {
 
 		//Verify the pad.length >= plainText.length, else return null
 		if (pad.length < plainTextCopy.length) {
-			System.out.println("Error: Failed OTP encoding. Pad length smaller than string length.");
-			return null;
+			System.out.println("Error: Failed OTP encoding. Pad length smaller than string length. Retry with a padlength >= text length.");
+			byte[] empty = {};
+			return empty; //Returns an empty string
 		}
 
 		for (int i = 0; i < plainTextCopy.length; ++i) {