I thought this forum would be able to provide the good gentleman with more accurate data that the typical that is to be found on the below mentioned mailing list. -- Yours, J.A. Terranson sysadmin@mfn.org "Every living thing dies alone." Donnie Darko ---------- Forwarded message ---------- Date: Fri, 31 Oct 2003 08:11:59 -0800 (PST) From: No Man <noman4222@yahoo.com> To: pen-test@securityfocus.com Subject: Cisco LEAP I'm sure everyone is aware of the recent discussion regarding LEAP and it's suceptiblity to dictionary attacks. As I understand it, it is basically the MS-CHAP problem: the 16 byte RC4 hash is padded with 5 nulls, split into three 7 byte chunks, then each chunk is encrypted with DES. The last chunk, since you know it has 5 nulls, is pretty easy to get That gives you the last two bytes of the hash, which you then compare for matches with the last two bytes in a precompiled dictionary of hashes. What about using a very large dictionary of all possible combinations for a given password length to, in effect, "brute force" it? Take for example a 6 character password made of lowercase letters and numbers. 36^6 works out to about 2.2 billion possibilities. Your dictionary or 2.2B rc4 hashes would take up roughly 40GB. I guess the plain text that the hash was calculated from would be in there too, so it would be a little larger, but suffice it to say that it would fit on a fairly typical hard drive. So, I'm wondering several things. Consider typical newer Intel hardware. 1) what would it take time-wise to create the dictionary? 2) how long would it take to cycle through 40 gigs of hashes to find the matches? 3) how many matches on the last two bytes of the hash are there likely to be? Thanks in advance for any help in deciding how big of an issue this really is! Michael __________________________________ Do you Yahoo!? Exclusive Video Premiere - Britney Spears http://launch.yahoo.com/promos/britneyspears/ --------------------------------------------------------------------------- Network with over 10,000 of the brightest minds in information security at the largest, most highly-anticipated industry event of the year. Don't miss RSA Conference 2004! Choose from over 200 class sessions and see demos from more than 250 industry vendors. If your job touches security, you need to be here. Learn more or register at http://www.securityfocus.com/sponsor/RSA_pen-test_031023 and use priority code SF4. ----------------------------------------------------------------------------