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Date: Thu, 02 Jul 2015 23:13:32 +0200
From: Marek Wrzosek <>
Subject: Re: LM and halves, length limit, does john "attack"
 halves together?


What is the purpose for Loopback rule in Rules? Rule NT is for cracking
NTLM hashes combining halves and toggling case. Split rule is for
cracking LM hashes (which are 7 char. max long) with passwords from
wordlist that are longer than 7. So why NT and Split are combined in
Loopback rule?

Best Regards,

W dniu 02.07.2015 o 22:40, Aleksey Cherepanov pisze:
> I'd like to know how john handles candidates in relation to halves of
> LMs?
> Let's consider "Password1" password. There will be 2 LMs with
> passwords: PASSWOR and D1 . Does john know that first 7 chars should
> be cut off? I don't see that in code.
> But I see a rule for that:
> # Used for loopback. This rule will produce candidates "PASSWOR" and "D" for
> # an input of "PASSWORD" (assuming LM, which has halves of length 7).
> [List.Rules:Split]
> :
> -s x**
> I find "Used for loopback" misleading because john (jumbo) stores
> truncated passwords in .pot. The rule is for original attack and it
> should be combined with other rules. Would not it be more convenient
> to do that in format itself?
> Thanks!

Marek Wrzosek

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