Thread: IllegalBlockSizeException Problem

I am working on a school project and am having a bit of a problem with the two following functions. If I use the ImportArray function it will throw an IllegalBlockSizeException: Input length must be multiple of 8 when decrypting with padded cipher. As far as I could tell that was because the byte arrays I was creating on the import from the input strings after they were split up were not the same as before. Perhaps I am viewing this all wrong. Any chance you could tell me where I have made a mistake here?

	public void ImportArray() throws Exception
	{
		FileReader inputFile = new FileReader("students.txt");
 
		Scanner scannedFile = new Scanner(inputFile);
		String buffer = null;
		String[] splitter;
 
		while (scannedFile.hasNext())
		{
			if(buffer == null)
			{
				buffer = scannedFile.next();
			}
			else
			{
				buffer = buffer + scannedFile.next();
			}
		}
		scannedFile.close();
 
		splitter = buffer.split(delimiter);
 
		for (int i = 0; i < splitter.length; i++)
		{
			Student ImportedStudent = new Student();
 
			String stemp1 = splitter[i];
			byte[] temp1 = stemp1.getBytes();
			byte[] temp2 = splitter[i+1].getBytes();
			byte[] temp3 = splitter[i+2].getBytes();
			byte[] temp4 = splitter[i+3].getBytes();
			byte[] temp5 = splitter[i+4].getBytes();
 
			String STemp1 = EMan.DecodeDataString(temp1);
			String STemp2 = EMan.DecodeDataString(temp2);
			String STemp3 = EMan.DecodeDataString(temp3);
			String STemp4 = EMan.DecodeDataString(temp4);
			String STemp5 = EMan.DecodeDataString(temp5);
 
			ImportedStudent.FirstName = STemp1;
			ImportedStudent.LastName = STemp2;
			ImportedStudent.CurrentTest = STemp3;
			ImportedStudent.CurrentGrade = Double.valueOf(STemp4);
			ImportedStudent.TestCompleted = Boolean.valueOf(STemp5);
 
			push(ImportedStudent);
			i = i + 4;
		}
	}
 
	public void ExportArray() throws InvalidKeyException, BadPaddingException, IllegalBlockSizeException, IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException
	{
		FileWriter  outputFile = new FileWriter ("students.txt", false);
 
		String encryptedStudent = "";
 
		for (int i = 0; i < StudentArray.length; i++)
		{
			Student ExportStudent = StudentArray[i];
 
			if(ExportStudent != null)
			{
				byte[] temp1 = EMan.EncodeDataString(ExportStudent.FirstName);	
 
				byte[] temp2 = EMan.EncodeDataString(ExportStudent.LastName);
 
				byte[] temp3 = EMan.EncodeDataString(ExportStudent.CurrentTest);
 
				String STemp1 = String.valueOf(ExportStudent.CurrentGrade);
				byte[] temp4 = EMan.EncodeDataString(STemp1);
 
				String STemp2 = String.valueOf(ExportStudent.TestCompleted);
				byte[] temp5 = EMan.EncodeDataString(STemp2);
 
				if(i > 0)
				{
					encryptedStudent = delimiter + temp1 + delimiter + temp2 + delimiter + temp3 + delimiter + temp4 + delimiter + temp5;
				}
				else
				{
					encryptedStudent = temp1 + delimiter + temp2 + delimiter + temp3 + delimiter + temp4 + delimiter + temp5;
				}
 
				outputFile.write(encryptedStudent);
			}
		}
		outputFile.close();
	}

Your code is using a lot of third party classes. There is no way we can help you use them.
If we were to help, You need to provide us with the import statements you use to compile your program and the API doc for all the third party classes you are using.

Is your code getting the exception when it executes
or is your code supposed to throw the exception when it detects the error?

The program stores student account information which would include first name, last name, what the name of the current test is, if the student has completed it, and if they have a grade for the test, what it is. After being encrypted, this information is all exported to a file called students.txt via a string with delimiters. The ImportArray Function is for the Instructor Role to be able to load a class list and view the information. It will have to be seperated back up into the byte arrays and decrypted. That is where the problem is.

I would move that there is something seriously wrong with you code if it is throwing all those exceptions that you have to handle. You should figure out what is throwing the exceptions and fix each one - one at a time.

Please post complete code and copy and paste the errors from the console so that we may further help you.

The complete code for this class:

 
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
 
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Scanner;
 
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
 
public class StudentManager 
{
	private static TestManager TMan;
	private static EncryptionManager EMan;
 
	protected final int DEFCAP = 50; //Maximum of number of Students per class
	protected Student[] StudentArray;  //Student Array
	protected int topIndex = -1;      // index of top element in stack
	private boolean classLoaded;
	private String delimiter = "-";
 
	private class Student extends Object
	{
		String FirstName = "John";
		String LastName = "Doe";
 
		String CurrentTest = "none";
 
		double CurrentGrade = 0.0;
 
		boolean TestCompleted = false;
	}
 
	public StudentManager(TestManager man) 
	{
		TMan = man; //The Test manager
 
		Student CurrentStudent = null; //For purpose of tracking logged in student performance
 
		StudentArray = new Student[50]; //Maximum of 50 Students per class
 
		classLoaded = false;
	}
 
	public void initialize() throws Exception
	{
		EMan = new EncryptionManager(TMan);
		EMan.initialize();
 
		testSystem();
    }
 
	public void ImportArray() throws Exception
	{
		FileReader inputFile = new FileReader("students.txt");
 
		Scanner scannedFile = new Scanner(inputFile);
		String buffer = null;
		String[] splitter;
 
		while (scannedFile.hasNext())
		{
			if(buffer == null)
			{
				buffer = scannedFile.next();
			}
			else
			{
				buffer = buffer + scannedFile.next();
			}
		}
		scannedFile.close();
 
		splitter = buffer.split(delimiter);
 
		for (int i = 0; i < splitter.length; i++)
		{
			Student ImportedStudent = new Student();
 
			String stemp1 = splitter[i];
			byte[] temp1 = stemp1.getBytes();
			byte[] temp2 = splitter[i+1].getBytes();
			byte[] temp3 = splitter[i+2].getBytes();
			byte[] temp4 = splitter[i+3].getBytes();
			byte[] temp5 = splitter[i+4].getBytes();
 
			String STemp1 = EMan.DecodeDataString(temp1);
			String STemp2 = EMan.DecodeDataString(temp2);
			String STemp3 = EMan.DecodeDataString(temp3);
			String STemp4 = EMan.DecodeDataString(temp4);
			String STemp5 = EMan.DecodeDataString(temp5);
 
			ImportedStudent.FirstName = STemp1;
			ImportedStudent.LastName = STemp2;
			ImportedStudent.CurrentTest = STemp3;
			ImportedStudent.CurrentGrade = Double.valueOf(STemp4);
			ImportedStudent.TestCompleted = Boolean.valueOf(STemp5);
 
			push(ImportedStudent);
			i = i + 4;
		}
	}
 
	public void ExportArray() throws InvalidKeyException, BadPaddingException, IllegalBlockSizeException, IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException
	{
		FileWriter  outputFile = new FileWriter ("students.txt", false);
 
		String encryptedStudent = "";
 
		for (int i = 0; i < StudentArray.length; i++)
		{
			Student ExportStudent = StudentArray[i];
 
			if(ExportStudent != null)
			{
				byte[] temp1 = EMan.EncodeDataString(ExportStudent.FirstName);	
 
				byte[] temp2 = EMan.EncodeDataString(ExportStudent.LastName);
 
				byte[] temp3 = EMan.EncodeDataString(ExportStudent.CurrentTest);
 
				String STemp1 = String.valueOf(ExportStudent.CurrentGrade);
				byte[] temp4 = EMan.EncodeDataString(STemp1);
 
				String STemp2 = String.valueOf(ExportStudent.TestCompleted);
				byte[] temp5 = EMan.EncodeDataString(STemp2);
 
				if(i > 0)
				{
					encryptedStudent = delimiter + temp1 + delimiter + temp2 + delimiter + temp3 + delimiter + temp4 + delimiter + temp5;
				}
				else
				{
					encryptedStudent = temp1 + delimiter + temp2 + delimiter + temp3 + delimiter + temp4 + delimiter + temp5;
				}
 
				outputFile.write(encryptedStudent);
			}
		}
		outputFile.close();
	}
 
	public void testSystem() throws Exception
	{
		Student NewStudent1 = new Student();
		NewStudent1.FirstName = "Nelson";
		NewStudent1.LastName = "Jones";
		NewStudent1.CurrentTest = "Summer2011";
		NewStudent1.CurrentGrade = 0.0;
		NewStudent1.TestCompleted = false;
		push(NewStudent1);
 
		Student NewStudent2 = new Student();
		NewStudent2.FirstName = "Ronald";
		NewStudent2.LastName = "Nelson";
		NewStudent2.CurrentTest = "Summer2011";
		NewStudent2.CurrentGrade = 0.0;
		NewStudent2.TestCompleted = false;
		push(NewStudent2);
 
		Student NewStudent3 = new Student();
		NewStudent3.FirstName = "Jacqueline";
		NewStudent3.LastName = "Ahner";
		NewStudent3.CurrentTest = "Summer2011";
		NewStudent3.CurrentGrade = 0.0;
		NewStudent3.TestCompleted = false;
		push(NewStudent3);
 
		ExportArray();
 
		ImportArray();
	}
 
	public boolean IsInClass()
	{
		if(classLoaded == false)
		{
			return false;
		}
		return false;
	}
 
	private class StudentArrayException extends RuntimeException
	{
		public StudentArrayException(String message)
		{
			super(message);
		}
	}
 
	public void push(Student studentAdd)
	{
		if (!isFull())
		{
			topIndex++;
			StudentArray[topIndex] = studentAdd;
		}
		else
			throw new StudentArrayException("Push attempted on a full stack.");
	}
 
	public void pop()
	{ 
		if (!isEmpty())
		{
	    	StudentArray[topIndex] = null;
	    	topIndex--;
	    }
	    else
	    	throw new StudentArrayException("Pop attempted on an empty stack.");
	}
 
	public Object top()
	{ 
		Object topOfStack = null;
		if (!isEmpty())
			topOfStack = StudentArray[topIndex];
		else
			throw new StudentArrayException("Top attempted on an empty stack.");
		return topOfStack;
	}
 
	public boolean isEmpty()
	{  
		if (topIndex == -1) 
			return true;
		else
			return false;
	}
 
	public boolean isFull()
	{   
		if (topIndex == (DEFCAP - 1)) 
			return true;
		else
			return false;
	}
}

The complete code for the encryption class:

import javax.crypto.Cipher;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
 
import java.io.UnsupportedEncodingException;
import java.security.Key;
import java.security.InvalidKeyException;
import java.security.SecureRandom;
 
public class EncryptionManager 
{
	private static TestManager TMan;
 
    private static Key key;
    private static Cipher cipher;
 
	public EncryptionManager(TestManager man) 
	{
		TMan = man; //The Test manager
		key = null;
		cipher = null;
	}
 
	public byte[] EncodeDataString(String importData) throws InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException
	{
		cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] exportData = importData.getBytes("UTF8");
        return cipher.doFinal(exportData);
	}
 
	public String DecodeDataString(byte[] importData) throws InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException
	{
		cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] recoveredBytes = cipher.doFinal(importData);
        String exportData = new String(recoveredBytes, "UTF8");
        return exportData;
	}
 
	public void initialize() throws Exception
	{
		KeyGenerator generator;
		generator = KeyGenerator.getInstance("DES");
		generator.init(new SecureRandom());
		key = generator.generateKey();
        cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
    }
}

Please copy and paste here the full text of your error messages.
To copy the contents of the command prompt window:
Click on Icon in upper left corner
Select Edit
Select 'Select All' - The selection will show
Click in upper left again
Select Edit and click 'Copy'

Paste here.

Everything from the Console"

Exception in thread "main" javax.crypto.IllegalBlockSizeException: Input length must be multiple of 8 when decrypting with padded cipher
at com.sun.crypto.provider.CipherCore.doFinal(CipherC ore.java:750)
at com.sun.crypto.provider.CipherCore.doFinal(CipherC ore.java:676)
at com.sun.crypto.provider.DESCipher.engineDoFinal(DE SCipher.java:314)
at javax.crypto.Cipher.doFinal(Cipher.java:2086)
at EncryptionManager.DecodeDataString(EncryptionManag er.java:35)
at StudentManager.ImportArray(StudentManager.java:94)
at StudentManager.testSystem(StudentManager.java:178)
at StudentManager.initialize(StudentManager.java:57)
at TestManager.InitializeCore(TestManager.java:45)
at TestManager.main(TestManager.java:31)

IllegalBlockSizeException: Input length must be multiple of 8 when decrypting with padded cipher

What is the length of the byte array that is passed to the doFinal method()?
Why isn't it a multiple of 8?

I understood that. However, I don't see what it would no longer have a length of 8. It had one before it was exported.

It's not a multiple of 8 because you only initalized the array of students. It is an empty array. It needs to be filled with data. Your export from the file is not going where it should.

Actually it is Spidey because I did it with the testSystem function I threw in there. There are three students added.

all I can tell you with the length is that if I do a System.err.print for byte[] temp1 in each of the functions, the ExportArray lenght comes up as 8816 and the ImportArray function has 111111. No earthly idea why.

Junky, I spent most of my day doing that very thing. All I know is that if System.err.print for byte[] temp1 throughout byte[] temp5 in the ExportArray function, they will look exactly the same to the strings splitter[i] through splitter[i+4] in the ImportArray function. As soon as you try to convert those strings over to byte arrays, it all falls apart.

Don't you think that splitter gets different bytes each time???
Try writing System.err.print under each line where you assigning splitter to byte and find the size of array. I guess if splitter is not getting multiple of 8.

Umm...actually I beleive the programming gods were seriously screwwing with me last night. Because I woke this morning, cleaned out a few little pieces of unused extra and this works now. Go figure.

@GeekWarth: Try to print the value of offset, if it's -1, then in the loop set condition as offset!=-1
Try this and share here.
Also, try to write a test program that compose of 5 to 10 lines so that everyone could help you and you could use that in your main program.