Not decrypting properly

[Jerry Girgich]

So I have encrypted a String with a secret key and encrypted the secret key with the public key and I am now decrypting. The code is running fine and I am running into no errors but it is not decrypting correctly. I am not getting the same key once decrypted since it is just giving me characters and my decrypted text is not the same either as it is also characters.


Here is my encryption and decryption code

public static String encrypt(String plainText, SecretKey secretkey) throws Exception {
		//Encodes the string into a sequence of bytes
		byte[] plainTextByte = plainText.getBytes();
		//intialize cipher to encryption mode
		cipher.init(Cipher.ENCRYPT_MODE, secretkey);
		//data is encrypted 
		byte[] encryptedByte = cipher.doFinal(plainTextByte);
		Base64.Encoder encoder = Base64.getEncoder();
		//encodes bytes into a string using Base64
		String encryptedText = encoder.encodeToString(encryptedByte);
		// return the string encrypted text to the main method
		return encryptedText;
		
	}
	
	public static String encryptedKey(PublicKey pk, SecretKey secretkey) throws Exception {
		// data written to byte array
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		// writes data types to the output stream
		ObjectOutputStream writter = new ObjectOutputStream(baos);
		//specific object of secretkey is written to the output stream
		writter.writeObject(secretkey);
		
		//creates a byte array  
		byte[] plainTextByteKey = baos.toByteArray();
	
		//creates a cipher using the RSA algorithm 
		Cipher cipher = Cipher.getInstance("RSA");
		// initalizes cipher for encryption using the public key 
		cipher.init(Cipher.ENCRYPT_MODE, pk);
		//encrypts data
		byte[] encryptedByteKey = cipher.doFinal(plainTextByteKey);
		
		Base64.Encoder encoderKey = Base64.getEncoder();
		// encodes the byte array into a string.
		String encryptedTextKey = encoderKey.encodeToString(encryptedByteKey);
		return encryptedTextKey;
		
	}
	
	private static String decryptedKey(PrivateKey myPrivateKey, String encryptedTextKey) throws Exception {
		
		String decryptedTextKey = new String(decryptedByteKey);
		return decryptedTextKey;
		
	}
	
	private static String decryptedTextKey(PrivateKey myPrivateKey, String encryptedText) throws Exception {
		byte[] decryptedByteText = Base64.getDecoder().decode(encryptedText);
		String decryptedText = new String(decryptedByteText);
		
		
		
		
		
		return decryptedText;
		
		
		
	}

[Jerry Girgich]

Never mind I am not decrypting with my private key like I need to which is the problem

[Henry Wong]

Neither one of your decrypting methods do any ... well ... decrypting...

[EDIT] response 30 seconds too late...

Henry

[Jerry Girgich]

Although I can't figure out the syntax for using Base 64 to decrypt the secret key

[Jerry Girgich]

How would I use Base64 for decoding, I keep getting errors when I try to do the opposite of how I encrypted

[Henry Wong]

Jerry Girgich wrote:Although I can't figure out the syntax for using Base 64 to decrypt the secret key

Base64 is *not* an encryption algorithm. It is an encoding algorithm, which is used to encode binary data into a text string. The idea is... with a text string, you can store it in a text file, or anywhere else, easier than you can with binary data.

Henry

[Jerry Girgich]

This is how I think I should be decrypting (not sure though)

private static String decryptedKey(PrivateKey myPrivateKey, String encryptedTextKey) throws Exception {
		
		ByteArrayOutputStream baosDecrypt = new ByteArrayOutputStream();
		ObjectOutputStream writterDecrypt = new ObjectOutputStream(baosDecrypt);
		writterDecrypt.writeObject(encryptedTextKey);
		byte[] byteKeyDecrypt = baosDecrypt.toByteArray();
		
		
		Cipher cipher;
		String decryptedKey = null;
		cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, myPrivateKey);
		byte[] decryptedByteKey = cipher.doFinal(byteKeyDecrypt);
		Base64.Decoder decoderKey = Base64.getDecoder();
		//String decryptedTextKey = decoderKey.decodeToString(byteKeyDecrypt);
		String decryptedTextKey = new String(byteKeyDecrypt);
		return decryptedTextKey;
	

I am getting this error though:

Exception in thread "main" javax.crypto.IllegalBlockSizeException: Data must not be longer than 256 bytes
	at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:344)
	at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:389)
	at javax.crypto.Cipher.doFinal(Cipher.java:2165)
	at ReadFileExample.generatekey.decryptedKey(generatekey.java:282)
	at ReadFileExample.generatekey.main(generatekey.java:218)

[Jerry Girgich]

How would I fix this error? Is there a better way to decode than what I did?

[Stephan van Hulst]

I don't understand why you're working with Strings in the first place. Why don't you just work with byte arrays?

Also, why are you not using Cipher.wrap() and Cipher.unwrap() to encrypt/decrypt your symmetric key?

[Jerry Girgich]

Stephan van Hulst wrote:I don't understand why you're working with Strings in the first place. Why don't you just work with byte arrays?

Also, why are you not using Cipher.wrap() and Cipher.unwrap() to encrypt/decrypt your symmetric key?

Well I am pretty new at all of this encryption and decryption so it would be great if you would actually help with what I have done instead of diminishing it completely.

[Stephan van Hulst]

I've given you pointers in all your previous threads and you've ignored them, so now I'm asking if you have good reasons to ignore them.

As Henry has pointed out before, you need to reverse your process. That doesn't just mean reverse the operations you perform, but also reverse the order of the operations. For instance, after you've encrypted your plaintext to a ciphertext and then encoded your ciphertext as base64, you can't decrypt the String before you decode it, because you need to decrypt the raw ciphertext, not the base64.

[Henry Wong]

Stephan van Hulst wrote:
As Henry has pointed out before, you need to reverse your process. That doesn't just mean reverse the operations you perform, but also reverse the order of the operations.

As another example, if you take a letter and seal it in an envelope; then take the envelope and lock it in a box; and then take that box and lock it in a safe.... the first step to undo everything, would not be to unseal the envelope...

Henry

[Jerry Girgich]

So I was finally able to decrypt the key like this:

	private static String decryptedKey(PrivateKey myPrivateKey, String hexEncryptedByteKey) throws Exception {
		
		//ByteArrayOutputStream baosDecrypt = new ByteArrayOutputStream();
		//ObjectOutputStream writterDecrypt = new ObjectOutputStream(baosDecrypt);
		//writterDecrypt.writeObject(hexEncryptedByteKey);
		//byte[] byteKeyDecrypt = baosDecrypt.toByteArray();
		
		
		Cipher cipher;
		cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, myPrivateKey);
		//cipher.doFinal();
		
		//byte [] decryptedKey = Base64.getDecoder().decode(byteKeyDecrypt);
		//String decryptedTextKey = new String(byteKeyDecrypt);
		
		byte[] decodedHex = DatatypeConverter.parseHexBinary(hexEncryptedByteKey);
		System.out.println("decoded hex key: " + decodedHex);
		String decryptedKey = new String(decodedHex, "UTF-8");
		return decryptedKey;
		
		
		
		
		
	}

I am now going to decrypt the encrypted String with this decrypted key. Since the decrypted key is in the format String , I need to convert it back into a Key so this is what I did:

	private static String decryptedTextHex(String decryptedKey, String hexEncryptedByteText) throws Exception {
		
		byte[] decryptedTextByte = decryptedKey.getBytes();
		
		SecretKeySpec key = new SecretKeySpec(decryptedTextByte, 0, decryptedTextByte.length, "AES");
		
		Cipher cipher;
		cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		
		cipher.init(Cipher.DECRYPT_MODE, key);
		byte[] decodedTextHex = cipher.doFinal(decryptedTextByte);
		String decryptedText = new String(decodedTextHex, "UTF-8");
		
		

	
		
		return decryptedText;
		
		
	
	}

I am getting this error though and I am not sure how to fix it:

Exception in thread "main" java.security.InvalidKeyException: Parameters missing
	at com.sun.crypto.provider.CipherCore.init(CipherCore.java:469)
	at com.sun.crypto.provider.AESCipher.engineInit(AESCipher.java:313)
	at javax.crypto.Cipher.implInit(Cipher.java:802)
	at javax.crypto.Cipher.chooseProvider(Cipher.java:864)
	at javax.crypto.Cipher.init(Cipher.java:1249)
	at javax.crypto.Cipher.init(Cipher.java:1186)
	at ReadFileExample.generatekey.decryptedTextHex(generatekey.java:288)
	at ReadFileExample.generatekey.main(generatekey.java:202)

[Jerry Girgich]

I want to change the code for the decryptedTextHex:

private static String decryptedTextHex(String decryptedKey, String hexEncryptedByteText) throws Exception {
		
		byte[] decryptedTextByte = decryptedKey.getBytes();
		byte[] textString = hexEncryptedByteText.getBytes();
		SecretKey key = new SecretKeySpec(decryptedTextByte, 0, decryptedTextByte.length, "AES");
		
		
		Cipher cipher;
		cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
		
		cipher.init(Cipher.DECRYPT_MODE, key);
		byte[] decodedTextHex = cipher.doFinal(textString);
		String decryptedText = new String(decodedTextHex, "UTF-8");
		
		
		return decryptedText;
		
		
	
	}

Realized I made a mistake but it still gives me the same error.

[Henry Wong]

Jerry Girgich wrote:So I was finally able to decrypt the key like this:

Your decryptedKey() method... well ... doesn't do any decrypting at all. From the looks of it, it is doing some XML parsing?

Why are you doing that? Totally confused...

Henry

[Jerry Girgich]

Henry Wong wrote:
Your decryptedKey() method... well ... doesn't do any decrypting at all. From the looks of it, it is doing some XML parsing?
Why are you doing that? Totally confused...

I am not sure, when my method was not working I googled some more and a lot of posts were saying to convert the byte to a String text which is what I did and I wasn't getting any errors from the code I posted.

[Jerry Girgich]

I think I am pretty much stuck and I am not sure how to go forward

[Stephan van Hulst]

Yeah, that's wrong. Strings have nothing to do with keys. For now, stop using strings. Stop using encodings. Your very first task is to encrypt a given message using a given key, and then to decrypt a message using a given key. Here are the method signatures. Show me how you would implement these, and then we'll move on to the rest of the tasks. You are NOT allowed to change the values of the constants I defined, and your are NOT allowed to change the method signatures and return types.

private static final String ENCRYPTION_ALGORITHM       = "AES";
private static final String TRANSFORMATION             = "AES/GCM/NoPadding";
private static final String RANDOM_GENERATOR_ALGORITHM = "SHA1PRNG";

private static final int INITIALIZATION_VECTOR_SIZE = 128;
private static final int AUTHENTICATION_TAG_SIZE    = 128;

/**
 * Encrypts the given plaintext message with the given secret key, using the AES/GCM algorithm.
 *
 * @param plaintext the message to encrypt
 * @param key       the key to encrypt the message with
 *
 * @return the encrypted message, concatenated with a randomly generated initialization vector
 *
 * @throws InvalidKeyException if the given key can not be used with AES/GCM
 */
private static byte[] encrypt(byte[] plaintext, SecretKey key) throws InvalidKeyException {
  throw new UnsupportedOperationException("Not implemented yet.");
}

/**
 * Decrypts the given ciphertext message with the given secret key, using the AES/GCM algorithm.
 *
 * @param ciphertext the message to decrypt, concatenated with the initialization vector that was used to encrypt the message
 * @param key        the key to decrypt the message with
 *
 * @return the decrypted message
 *
 * @throws InvalidKeyException if the given key can not be used with AES/GCM
 * @throws BadPaddingException if the ciphertext and the key don't match
 */
private static byte[] decrypt(byte[] ciphertext, SecretKey key) throws InvalidKeyException, BadPaddingException {
  throw new UnsupportedOperationException("Not implemented yet.");
}

[Henry Wong]

I only partially agree with Stephan here...

On the agreement part ... The encryption side, as implemented, is convoluted and messy. So, the decryption side is, at best, going to be the same. Perhaps, it is better to start over. To work on the encryption/decryption portion only. To work on both together, and confirms that it works.... and later, once that part works, then add any encoding, which again, to be done together.

On the disagreement part... The encryption side is mostly done.  And the decryption side, from earlier posts, is in much better shape. Additionally, Stephan and I had provided many hints, that for the most part has been ignored.  Perhaps, it is better to revisit all the old posts, from this topic and earlier topics. Start from older code. Look at all the previous hints, and make an attempt from there.

Jerry Girgich wrote:I think I am pretty much stuck and I am not sure how to go forward

To me, either option mentioned would work at getting you forward.  On the other hand, just guessing via code snippets from Google, probably won't work. As you noticed, this can actually get you moving backwards...

Henry