A Really Good Article on How Easy it Is to Crack Passwords

Ars Technica gave three experts a 16,000-entry encrypted password file, and asked them to break them. The winner got 90% of them, the loser 62% — in a few hours.

The list of “plains,” as many crackers refer to deciphered hashes, contains the usual list of commonly used passcodes that are found in virtually every breach involving consumer websites. “123456,” “1234567,” and “password” are there, as is “letmein,” “Destiny21,” and “pizzapizza.” Passwords of this ilk are hopelessly weak. Despite the additional tweaking, “p@$$word,” “123456789j,” “letmein1!,” and “LETMEin3” are equally awful…. As big as the word lists that all three crackers in this article wielded — close to 1 billion strong in the case of Gosney and Steube — none of them contained “Coneyisland9/,” “momof3g8kids,” or the more than 10,000 other plains that were revealed with just a few hours of effort. So how did they do it? The short answer boils down to two variables: the website’s unfortunate and irresponsible use of MD5 and the use of non-randomized passwords by the account holders.

The article goes on to explain how dictionary attacks work, how well they do, and the sorts of passwords they find.

Steube was able to crack “momof3g8kids” because he had “momof3g” in his 111 million dict and “8kids” in a smaller dict. “The combinator attack got it! It’s cool,” he said. Then referring to the oft-cited xkcd comic, he added: “This is an answer to the batteryhorsestaple thing.” What was remarkable about all three cracking sessions were the types of plains that got revealed. They included passcodes such as “k1araj0hns0n,” “Sh1a-labe0uf,” “Apr!l221973,” “Qbesancon321,” “DG091101%,” “@Yourmom69,” “ilovetofunot,” “windermere2313,” “tmdmmj17,” and “BandGeek2014.” Also included in the list: “all of the lights” (yes, spaces are allowed on many sites), “i hate hackers,” “allineedislove,” “ilovemySister31,” “iloveyousomuch,” “Philippians4:13,” “Philippians4:6-7,” and “qeadzcwrsfxv1331.” “gonefishing1125” was another password Steube saw appear on his computer screen. Seconds after it was cracked, he noted, “You won’t ever find it using brute force.”

Great reading, but nothing theoretically new. Ars Technica wrote about this last year, and Joe Bonneau wrote an excellent commentary.

Password cracking can be evaluated on two nearly independent axes: power (the ability to check a large number of guesses quickly and cheaply using optimized software, GPUs, FPGAs, and so on) and efficiency (the ability to generate large lists of candidate passwords accurately ranked by real-world likelihood using sophisticated models).

I wrote about this same thing back in 2007. The news in 2013, such as it is, is that this kind of thing is getting easier faster than people think. Pretty much anything that can be remembered can be cracked.

If you need to memorize a password, I still stand by the Schneier scheme from 2008:

So if you want your password to be hard to guess, you should choose something that this process will miss. My advice is to take a sentence and turn it into a password. Something like “This little piggy went to market” might become “tlpWENT2m”. That nine-character password won’t be in anyone’s dictionary. Of course, don’t use this one, because I’ve written about it. Choose your own sentence — something personal.

Until this very moment, these passwords were still secure:

WIw7,mstmsritt… = When I was seven, my sister threw my stuffed rabbit in the toilet.

Wow…doestcst::amazon.cccooommm = Wow, does that couch smell terrible.

Ltime@go-inag~faaa! = Long time ago in a galaxy not far away at all.

uTVM,TPw55:utvm,tpwstillsecure = Until this very moment, these passwords were still secure.

You get the idea. Combine a personally memorable sentence, some personal memorable tricks to modify that sentence into a password, and create a long-length password.

Better, though, is to use random unmemorable alphanumeric passwords (with symbols, if the site will allow them), and a password manager like Password Safe to store them. (If anyone wants to port it to the Mac, iPhone, iPad, or Android, please contact me.) This article does a good job of explaining the same thing. David Pogue likes Dashlane, but doesn’t know if it’s secure.

In related news, Password Safe is a candidate for July’s project-of-the-month on SourceForge. Please vote for it.

EDITED TO ADD (6/7): As a commenter noted, none of this is useful advice if the site puts artificial limits on your password.

EDITED TO ADD (6/14): Various ports of Password Safe. I know nothing about them, nor can I vouch for their security.

Analysis of the xkcd scheme.

Posted on June 7, 2013 at 6:41 AM • 147 Comments