Cracking the code?

Allen netsecurity at
Sat Mar 3 07:09:36 EST 2007

Hi gang,

On recent consulting gig, I came across what I think is a 
potential vulnerability and wanted to see how crazy my thinking is.

Without mentioning the exact place or piece of software because 
of NDAs, here is the basic scenario.

The tool stores the hex version of the remote access password in 
a field that is visible to the end user. The default setting of 
the software is that if you enter ASCII into the field, it will 
calculate the hex version and display it. At this site the sys 
admins have decided that this is not a user settable field so 
once set the user can not change it except with the help of an 
admin. There is also no policy in place to require periodic 
password changes.

Also every user in the entire enterprise has this field visible 
in their LDAP address information that anyone in the company can 
access at any time. The address info also contains the user name 
for logging onto the network. The password for remote access 
appears to be the same as the password for logging onto the 
machine even when it it not connected to the domain.

Next, trial versions of the software are available that still 
have the default setting where the user can enter any password 
and the hex value will be shown. As to the password algorithm 
itself, I don't know what it is. I don't know if it uses an IV 
that changes for every password that is entered, but that would 
be easy to check with the trial version. What research I've done 
says that it is derived from AES128 and it is a fixed field 
length. There is more than a bit of security by obscurity at play 

So it seems to me this is vulnerable to a know text attack: i.e., 
enter "known password 1" get back "hex value 1", etc. By hand it 
would take a while to build a list of equivalences, but I assume 
that a clever perl hacker, which I'm not, could code a widget 
that would automate this, taking a common dictionary such as from 
Cain & Abel, John the Ripper or some such, and fairly quickly 
build a list of password/hex pairs. With this list in hand an 
insider bent on industrial espionage could find the weak 
passwords of sys admins and logon as them and do whatever 
nefarious deeds they wish.

My questions are: A) is this as vulnerable as it seems at first 
blush? B) how many password/hex pairs would be needed to deduce 
the underlying algorithm?, C) If one could deduce the algorithm, 
could the attack be generalized so that it could be used against 
other enterprises that use the same software? (It is very(!) 
widely deployed), and D) am I missing something in my thinking?



The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at

More information about the cryptography mailing list