Encripting with PBE key

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krzysztof.murkowski@gmail.com - 04 Oct 2007 15:58 GMT

Hi,

I'm trying to encript simple text with PBE key which is generated from
the password.
This code is generating the same output for the different passwords.
What's wrong?

Thanks a lot for your help,
Krzysztof

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;

public class Test05
{
public static void main( String args[] ) throws Exception
{
/*
byte[] salt = {
(byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
(byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
};
int iterationCount = 19;
*/
String password = "password";
// String password = "different password";

// PBEKeySpec keySpec = new PBEKeySpec( password.toCharArray(), salt,
iterationCount, 8 );
PBEKeySpec keySpec = new PBEKeySpec( password.toCharArray() );
System.out.println( "keySpec: " + keySpec.getPassword() );

SecretKeyFactory keyFactory =
SecretKeyFactory.getInstance( "PBE" );
System.out.println( "keyFactory: " + keyFactory.getAlgorithm() );

SecretKey key = keyFactory.generateSecret( keySpec );
System.out.println( "key: " + key.getAlgorithm() );

Cipher cipher = Cipher.getInstance( key.getAlgorithm() );
System.out.println( "cipher.getInstance" );

cipher.init( Cipher.ENCRYPT_MODE, key );
System.out.println( "cipher.init" );

String input = "open text to be encrypted";
System.out.println( cipher.doFinal( input.getBytes() ) );
}
}

Reply to this Message

rossum - 04 Oct 2007 17:33 GMT

>Hi,
>
[quoted text clipped - 29 lines]
> PBEKeySpec keySpec = new PBEKeySpec( password.toCharArray() );
> System.out.println( "keySpec: " + keySpec.getPassword() );

getPassword() returns an array of char. toString(), which is called
in the background of your println(), will treat this as an array. You
will get "C[XXXXXX", where the X are hex digits making up the hash
code of the array. This is probably not what you were expecting. You
need to explicitly convert the returned char[] to a String for it to
print the actual contents of the array.

> SecretKeyFactory keyFactory =
>SecretKeyFactory.getInstance( "PBE" );
> System.out.println( "keyFactory: " + keyFactory.getAlgorithm() );

Different passwords will not change the algorithm, so you will always
get the same output here from getAlgorithm().

> SecretKey key = keyFactory.generateSecret( keySpec );
> System.out.println( "key: " + key.getAlgorithm() );

Ditto.

> Cipher cipher = Cipher.getInstance( key.getAlgorithm() );
> System.out.println( "cipher.getInstance" );
[quoted text clipped - 4 lines]
> String input = "open text to be encrypted";
> System.out.println( cipher.doFinal( input.getBytes() ) );

Again, you will not get the contents of the array, just "B[XXXXXX".

rossum

> }
>}

Reply to this Message

Roedy Green - 05 Oct 2007 01:10 GMT

> Cipher cipher = Cipher.getInstance( key.getAlgorithm() );

I think your biggest problem is here. It would be obvious if you
printed out key.getAlgorithm() which is a String.

Look at the Javadoc for Cipher.getInstance.

public static final Cipher getInstance(String transformation)
...
Parameters:
transformation - the name of the transformation, e.g.,
DES/CBC/PKCS5Padding. See Appendix A in the Java Cryptography
Extension Reference Guide for information about standard
transformation names.

cipher knows the algorithm to use, but not the key.

you need a cipher.init to tell it the secret key.

Signature

Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com

Reply to this Message

krzysztof.murkowski@gmail.com - 05 Oct 2007 20:09 GMT

Hi,

thanks a lot for all very useful hints.
Below the working code.

regards,
Krzysztof

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

public class Test05
{
public static void main( String args[] ) throws Exception
{

byte[] salt = {
(byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
(byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
};
int iterationCount = 19;

String password = "password";
// String password = "different password";

PBEKeySpec keySpec = new PBEKeySpec( password.toCharArray(), salt,
iterationCount, 8 );
System.out.println( "keySpec: " +
String.valueOf( keySpec.getPassword() ) );
System.out.println( "keySpec: " + keySpec.getKeyLength() );

PBEParameterSpec paramSpec = new
PBEParameterSpec( keySpec.getSalt(), keySpec.getIterationCount() );

SecretKeyFactory keyFactory =
SecretKeyFactory.getInstance( "PBE" );
System.out.println( "keyFactory: " + keyFactory.getAlgorithm() );

SecretKey key = keyFactory.generateSecret( keySpec );
System.out.println( "key: " + key.getAlgorithm() );

Cipher cipher = Cipher.getInstance( key.getAlgorithm() );
System.out.println( "cipher.getInstance" );

cipher.init( Cipher.ENCRYPT_MODE, key, paramSpec );
System.out.println( "cipher.init" );

String sinput = "clear text";
System.out.println( "-> " + sinput );
byte bencrypt[] = cipher.doFinal( sinput.getBytes() );

Cipher dcipher = Cipher.getInstance( key.getAlgorithm() );
dcipher.init( Cipher.DECRYPT_MODE, key, paramSpec );

byte bdecrypt[] = dcipher.doFinal( bencrypt );

String soutput = new String( bdecrypt );
System.out.println( "<- " + soutput );
}
}

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Encripting with PBE key

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