Re: Microsoft weak encryption

[Frank Andrew Stevenson <frank@funcom.no>]

I have been able to verify the key generation for the
.pwl file, and sucessfully decrypted one, the contets
is really suited for a known plaintext attack as the
first characters appears to be the USERNAME in capitals
padded with 0x00 to a total field size of 20,
I have written software to bruteforce this field, but without
optimizing I have a running time of 130 hours (Pentium 66)

An interesting observation: If the password is shared with a UNIX
fileserver (8 letters) once the 32 bit RC4 key is found guessing the
last 4 letters of the password will reveal the remaining letters.
This will then greatly reduce the keyspace needed to crack the UNIX
password (you need to guess the case of the password though - (2^8) )  

> Peter Gutmann has an interesting article in sci.crypt, demonstrating how
> weak Microsoft's encryption is with basic access control in Windows for
> Workgroups (I'm assuming Win95 uses the same algorithm).  Essentially, he
> shows how a 32-bit key is created to be passed to RC4 for encrypting .PWL
> files.  I think a t-shirt is definitely in order for this.
> 
> Anyone up for writing some bruting code?
> 
> Joel
> 

#include <std/disclaimer.h> 
E3D2BCADBEF8C82F A5891D2B6730EA1B PGPencrypted mail preferred, finger for key