Question about FAST

[kristian]

On 9/7/10, Henry B. Hotz <hotz at jpl.nasa.gov> wrote :

> John the Ripper supports single-des keys, and I think it requires an
AFS3 salt as well.  
> Neither of those are enabled by default in current
installations.

They claim that JTR can decrypt TGT of kerberos V5, but where can I get the AS_REP hex string to be decrypted? Instead the hex string of ticket in AS_REP always changes and the code entered in JTR must be static, I think.
So, any idea how to decrypt AS_REP to get the ticket by performing offline dictionary attack ?