Showing posts from April, 2010

Optimizing JtR's Single Mode Follow Up

Over at the John the Ripper mailing list , (I'm sure you already belong to it right?!), SolarDesigner, the creator of JtR, raised the following question about the re-ordered Single Mode rule-set I released last night. It is not clear whether you have full (or any) separation between your training and test sets when you re-order the rules. (You do say that you have such separation for your "UnLock" test, but that's another one.) In other words, the improvement from "Original Single Rules" to "Edited Single Version 2" that you've demonstrated might be partially attributable to you training (re-ordering) the rules on the same set that you later test them on. It's a valid question and it's something I've worried about myself. Referring back to my original post : For the target set, the RockYou list seemed like an obvious choice. I actually used a subset of the RockYou list of one million passwords I designated for training purposes, (t

Optimizing John the Ripper's "Single" Mode for Dictionary Attacks

While I've been doing a lot of analysis, I figure it's been a while since I actually released anything. That obviously needs to change. As one small step in the right direction, I decided to optimize John the Ripper's "Single" mode word mangling rules for use in normal dictionary based attacks. If you don't want to read through the rest of this post on my methodology, you can grab the new rule-set right here . To make use of it in a cracking session, simply enter the flag: -rules=Modified_Single For a more detailed explanation on what I did, please read on. The Problem: First of all, did you know that starting with John the Ripper version 1.7.4 you can have multiple rulesets in the same john.conf config file? Also SolarDesigner added a several new mangling rules, (such as the ability to insert/append whole strings), and increased the speed at which the mangling rules generate guesses. I know the current 1.7.5 branch is still not considered the stable version,

State of the Blog: April Edition

*Comic courtesy of Well, it looks like after three years of work, I did it . I'm still putting some last minute touches on my dissertation but once that's finalized I'll post a copy. The crazy thing is that after going through all of that, I'm actually more motivated to do research. So that leads us to this blog. Don't worry, it's not going away. In fact one of my prerequisites for any new job I get is that I need to be allowed to keep on updating here. As far as posts go, I'm going to be shifting away from brute force attacks and start talking about dictionary attacks instead. I know, I've maintained this blog for over a year and I'm only getting to that now... Let me explain: 1) I'm lazy 2) My main area of study has been designing new ways to represent how people create passwords using probabilistic context free grammars. At it's heart this approach is an improvement to standard dictionary based attacks, though I&