Solved

Java JCE : IllegalBlockSize Exception

Posted on 2003-11-03
5
707 Views
Last Modified: 2012-06-21
Hi guyz,
  Could somebody please help me out with this........I cant for the life of me figure out why an IllegalBlockSize Exeception is being thrown.........



package Crypto;

import java.security.*;
import javax.crypto.*;
import sun.misc.*;

public class KryptonTest {
   
   
   
public static void main (String[] args) throws Exception {
    String ClearText = "dazzman123";
    System.out.print("Attempting to get a Blowfish key");
    KeyGenerator keyGenerator = KeyGenerator.getInstance("Blowfish");
    keyGenerator.init(128);
    SecretKey key = keyGenerator.generateKey();
    System.out.println("OK");
   
    System.out.print("Attempting to get a cipher and encrypt");
    Cipher cipher = Cipher.getInstance("Blowfish/ECB/PKCS5Padding");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    byte [] cipherText = cipher.doFinal(ClearText.getBytes("ASCII"));
           
    String playitbaby = cipherText.toString();
    System.out.println(playitbaby);
   

   
    byte [] decrypted = playitbaby.getBytes("ASCII");
   
     
    cipher.init(Cipher.DECRYPT_MODE, key);
   
   
    byte [] decryptedtext = cipher.doFinal(decrypted);


   
    String output = decryptedtext.toString();
   
    System.out.println (output);
 
   
    System.out.println("Test Completed Successfully");
----------------------------------------------------------------------------




Attempting to get a Blowfish keyOK
Attempting to get a cipher and en
javax.crypto.IllegalBlockSizeException: Input length (with padding) not multiple of 8 bytes
        at com.sun.crypto.provider.BlowfishCipher.a(DashoA6275)
        at com.sun.crypto.provider.BlowfishCipher.engineDoFinal(DashoA6275)
        at com.sun.crypto.provider.BlowfishCipher.engineDoFinal(DashoA6275)
        at javax.crypto.Cipher.doFinal(DashoA6275)
        at Crypto.KryptonTest.main(KryptonTest.java:60)crypt[B@5d56d5
 
0
Comment
Question by:dazz_man
  • 2
5 Comments
 
LVL 3

Expert Comment

by:savalou
ID: 9672167
You should decrypt cipherText, not playitbaby.

cipherText.toString() isn't going to give you a string representation of the array, that gives you the object reference of the array.   Your encrypted message is not text, it's binary and may not be printable text.  If you want to know what the bytes are, print them out one-by-one in a for loop and you'd have some idea.

0
 
LVL 3

Accepted Solution

by:
savalou earned 25 total points
ID: 9672181
Sorry, decrypt cipherText, not decrypted.

So
 byte [] decryptedtext = cipher.doFinal(decrypted); // no
becomes
 byte [] decryptedtext = cipher.doFinal(cipherText); //
0
 

Assisted Solution

by:Ananthalakshmi
Ananthalakshmi earned 25 total points
ID: 9676407
Hi,
Visit http://forum.java.sun.com/thread.jsp?thread=454515&forum=9&message=2075112.

The following is an extract from the above site.

========================================================
IllegalBlockSize is the result of not using padding and or providing an invalid input length.

DES is a block cipher which requires at least 8 bytes of data and a total divisable by 8 bytes. That is unless you use a padding scheme which ensures it is a multiple of 8 bytes.

AES has a 16 byte block size. It must have 16 bytes of data input to do a single crypt operation. Total input length must be a multiple of 16 bytes.

The easiest way to deal with this is to use padding. PKCS5Padding as an example. Now padding will result in your output ciphertext being larger than your input plaintext (because of the pad bytes) but it will ensure you never get that error. Another solution is to use a stream mode such as CFB8 or CTR mode. This does not require padding and allows a block cipher such as DES, DESede, AES, etc to behave like a stream cipher. (aka doesn't care how much input you give it)... And finally, you can use a Stream cipher. Something like RC4 for example.

============================================================

Thanks,
H.Ananthalakshmi.
0

Featured Post

6 Surprising Benefits of Threat Intelligence

All sorts of threat intelligence is available on the web. Intelligence you can learn from, and use to anticipate and prepare for future attacks.

Join & Write a Comment

For customizing the look of your lightweight component and making it look opaque like it was made of plastic.  This tip assumes your component to be of rectangular shape and completely opaque.   (CODE)
Are you developing a Java application and want to create Excel Spreadsheets? You have come to the right place, this article will describe how you can create Excel Spreadsheets from a Java Application. For the purposes of this article, I will be u…
Viewers learn how to read error messages and identify possible mistakes that could cause hours of frustration. Coding is as much about debugging your code as it is about writing it. Define Error Message: Line Numbers: Type of Error: Break Down…
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…

746 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now