Date: Tue, 7 Aug 2012 00:32:28 -0400 From: "Matt Weir" <cweir@...edu> To: <john-users@...ts.openwall.com> Subject: Matt's writeup for Crack Me If You Can 2012 First of all I want to acknowledge the work Kevin Young did. He's another password cracking researcher who's been investigating passphrases, (you can see an article he was interviewed for here: http://www.computerworld.com/s/article/9227894/How_Charles_Dickens_helped_cr ack_your_LinkedIn_password). I met him at Defcon and he wanted to help out, and since he was dealing with internet connectivity issues like I was it turned out to be easier for him to just give me his cracked passwords and have me upload them to our server vs. him registering as another member on our team. Pretty much all the passphrases I uploaded were ones that he had cracked. I'm not sure about the exact hardware he used, but I'm pretty sure it was just a laptop he had left running in his hotel room. As far as my own contributions go, I was the team representative at Defcon so I hung out at the Korelogic booth when I could and I picked up the registration serial number. The only computer I had this year was my macbook pro so I did all my cracking on that. Also the only password cracking program I used was JtR 1.7.9-jumbo6, (though I did use several custom scripts to generate guesses). When the contest began Thursday night I initially started cracking the raw-sha1 hashes to try and grab some plaintexts and figure out patterns. I ran a bunch of dictionaries through it using the "single" ruleset. I also used the korelogic ruleset for some of the smaller dictionaries. At the same time I had an incremental=all attack running so I could try to identify patterns I didn't know about. Based on the cracked passwords I saw I created several JtR mangling rules and sent them out to our contest listserv. Throughout the contest I added to, deleted, and modified these rules but unfortunately I never got around to sending updates to the list due to my spotty internet access. I really kind of regret that. Friday morning/afternoon I ended up having to devote my CPU power to helping my CTF team try and crack several PGP encrypted files, (turns out they weren't encrypted with a passphrase after-all), so I wasn't very productive, but I moved on to cracking several of the other hash types Friday night using my custom rules. Saturday morning there were three very good password cracking talks that I'd recommend checking out the slides for. The Hash dumping talk was very useful to me since I've run into that problem a lot in the past and every time it happened I felt like I was going crazy (http://defcon.org/html/defcon-20/dc-20-speakers.html#Reynolds).The talk on breaking MSCHAPv2 was also excellent (http://defcon.org/html/defcon-20/dc-20-speakers.html#Marlinspike), along with bitweasil's talk on his GPU crackers, (http://defcon.org/html/defcon-20/dc-20-speakers.html#Bitweasil). I hope bitweasil is able to help our team out next year since all of his stuff is opensource. Saturday I focused on re-mangling the previous cracked passwords our team had cracked and trying them against the different hash types. Beyond running the plains through several mangling rules, I also did things like strip the digits/special characters out to extract the basewords, and concatenate the cracked passwords and then mangle them. I also had enough cracked passwords to train my probabilistic cracker, (it's really just a rule generator), on them and then run cracking sessions using that. I've made some improvements to my probabilistic cracker since the last contest and I just need to polish it up a bit before I release a new version to everyone else, but I was actually very happy with how it ran this year. It was a lot easier than writing mangling rules by hand, that's for sure! I just wish I had more time to run cracking sessions using it. Around 6:00pm I made it back to my hotel room and spend the next couple of hours running short cracking sessions against all the hash types, (with the exception of the really computationally expensive hashes), so that way I could maximize the number of hashes I cracked, (vs. focusing on one hash type exclusively and only cracking a few for the extra effort I put into it). At 11:30 I called it a night, but I have to admit I spent the next 30 minutes obsessively checking the scoreboard. It was a exciting finish! I'd really like to thank Korelogic for the work they did putting this contest on. The amount that this contest is spurring research and development is amazing, and their company has put in a ton of work over the last couple of years making this a reality. I expect there's a lot of people who are going to be looking into passphrases over this next year due their prevalence in the contest this year ;p I do have two suggestions that I would make for next year but these are just personal preferences: 1) Have a higher cap for the file challenges so the big teams are forced to develop tools to support additional file encryption types. I appreciate that Korelogic tried to provide incentive to smaller teams, but I don't know how well that worked out in reality. Maybe have puzzle challenges instead for individuals/small groups. For example provide information about a target and have people try to crack that target's password. Make these puzzles worth no points for the overall contest, but keep the donation prize for whoever cracks it so that way individuals can work on those to help a good cause. That would also provide more incentive to individuals since they are unlikely to win the contest anyway while discouraging the big teams from scooping up all the challenges since they wouldn't be worth any point to them. 2) I'd love to see the number of hash types reduced and have additional categories based on password creation policies added in their place. Aka have a category for passwords that are at least 15 characters long and contain uppercase/lowercase/special/digits. My reasoning behind this is that the major password cracking tools have strong support for many of the hash types already so I'd like to see some of the focus shift to attacking password creation policies instead. The researcher in me would also love to see the results of how effective those policies turn out to be in practice. All in all I had a great time. Thanks everyone! *I'd like to also say it was a classy move when team Hashcat submitted all of their cracked hashes early Saturday afternoon instead of holding them back. I know there's strategy in holding hashes back, but in the spirit of being a good sport I think in future contests we should follow their lead and release hashes as we crack them, (or at least as soon as it becomes easy to). Matt Weir
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