Java Security

Hi,
Seems like a password can be discovered based on the encrypted value of a former known password (when using the same key).

E.g.
In case I have a clear password: AAA
and I have the enrypted password as bytes :crypt(AAA).

I can decrypt any other password based on the Xor result of the clear & encrypted password : (AAA xor crypt(AAA))
BBB = crypt(BBB) xor (AAA xor crypt(AAA))
Looks like a security problem.
Is this a java bug or mine?
BTW when using AES/CFB8/NoPadding , this is not happening.

Here is the Code Example:

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;

public class MyTest
{
	static SecretKey m_secretKey = null;

	public static void main(String[] args)
	{
		try
		{
			MyTest test = new MyTest();
			test.init();
			test.encrypttionBreak();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}

	}

	private void init() throws Exception
	{
		if (m_secretKey == null)
			m_secretKey = KeyGenerator.getInstance("AES").generateKey();
	}



	private byte[] aesEncrypt(byte[] data, int mode) throws Exception
	{
		byte[] m_iv = new byte[16];

		for (int i = 0; i < m_iv.length; i++)
		{
			m_iv[i] = (byte) i;
		}

		IvParameterSpec iv = new IvParameterSpec(m_iv);
		Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding", "SunJCE");
		cipher.init(mode, m_secretKey, iv);

		byte[] cipherInput = cipher.doFinal(data);

		return cipherInput;
	}

	public void encrypttionBreak() throws Exception
	{
		String clearText = "aaaaaaaaaaaa";
		byte[] cipherBytes = aesEncrypt(clearText.getBytes(),
			Cipher.ENCRYPT_MODE);

		byte clearBytes[] = clearText.getBytes();
		byte xorKey[] = new byte[clearBytes.length];
		for (int i = 0; i < xorKey.length; i++)
		{
			xorKey[i] = (byte) (clearBytes[i] ^ cipherBytes);

		}



		String password = "mypass";



		byte[] passwordEncrypted = aesEncrypt(password.getBytes(),

			Cipher.ENCRYPT_MODE);



		byte breakFinal[] = new byte[passwordEncrypted.length];

		for (int i = 0; i < breakFinal.length; i++)

		{

			breakFinal[i] = (byte) (passwordEncrypted[i] ^ xorKey[i]);

		}



		System.out.println("break final " + new String(breakFinal));



	}



}





Edited by: sabre150 on 19-Aug-2011 02:37



Moderator: added [ code] tags to make the code readable.