Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 4 May 2017 23:56:38 +0200
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: Max characters for password candidates (NTLM) and
 others

On 2017-05-04 23:44, Frank Dittrich wrote:
 > Am 04.05.2017 um 23:27 schrieb magnum:
 >> The NT formats have a max length of 27 *characters* (for performance
 >> reasons).
 >
 > The 27 character limit isn't really a hash format limitation, but a
 > limitation of John's NT format implementation, ist that correct?
Correct. Off the top of my head, the actual maximum in Windows is 255 
characters.

 > So, it would be possible to drop that limit (or change the limit from
 > currently 27 characters to, say, 54 characters).
Sure. We could support any length but it'd be slower. Actually, for a 
non-SIMD build (eg. non-Intel using OpenSSL) I think our limit is 125 
bytes (which is the hard deck no-matter-what, set by legacy core code) 
and that'd be just 41 characters worst case (that is, every one of them 
take three bytes to represent in UTF-8).

 > But trying password candidates that are longer than 27 characters would
 > reduce the cracking speed to about half the speed of the current
 > implementation.
Actually we could implement some kind of branching and support 
27/54/81/108/125 bytes, no problem. And we could re-write John's core 
and support more than 125 bytes. But with fast hashes like NT the 
branching would be a significant regression. It would hurt real-world 
cracking: No-one has a password of 27 characters, let alone longer.

 > Does hashcat also have a 27 character limit for NT format?
Sure. In our world of Merkel-Damgård geeks, it's a perfectly even 
number. In non-unicode formats like raw-md4/md5, it's 55. Actually in NT 
it's 27.5 but that obviously doesn't make sense.

magnum

Powered by blists - more mailing lists

Your e-mail address:

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.