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Re: passwd hashing algorithm (fwd)Dr. Frederick B. Cohen (fcall.net)
Fri, 14 Apr 1995 07:47:19 -0400 (EDT)
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> I think you're off base. :) The weakness involves the speed > with which you can des data. Doing to 3des means you (roughly) triple > the attack time, which means that in about 2 years, we'll be back > where we are today. Remember that Crack doesn't really crack > passwords, it just tries to send in lots of passwords, and see when > the output matches. > > What you want is a strong authenticating function; something > that the user can do to demonstrate identity (and possibly possession) > to a server. I doubt that reusable passwords are up to the task, > unless you're using some solid encryption client. If you're going to > build a smart client, you might as well build in smart authentication. There is a core issue here that these technical points miss. The issues that underly weak passwords are people problems, not technical problems. The reason people choose weak passwords is partly a lack of education and partly a lack of desire by people to change themselves to meet the needs of a computer. If a large portion of people aren't willing to use a hard-to-guess 8 character giberish string, what makes us think they will be willing to carry a smart-card or use some authentication device or procedure, or learn to do something secret? In terms of the use of Crack and other similar programs, I have run these techniques against a few hundred password files, and I almost always find that if Crack doesn't get them in 15 minutes, the other several hours of effort it puts forth are wasted. In other words, we have trivial passwords and reasonable passwords. Trivial ones account for 25-40%. We could eliminate the threat from Crack by simply using a password tester on passwords as they are created. These are easy to write and several are commercially available. Systems administrators and manufacturers are apparently unwilling to go to even this much trouble, so why should users bother or care? Finally, in terms of making it harder to run Crack and other such programs, we could greatly complicate their job by having a SECRET key that is unique to each system instead of a salt that is easily found by examining the password file. If done properly, this could essentially eliminate ALL such guessing attacks not involving knowledge of the secret key. OK, I'm ready to be rebuffed! -- ----------------- \Management /\/| 216-686-0090 - PO Box 1480, Hudson, OH 44236 \ /\/ | Check out info-security heaven and test your system \/\ /\/ | for known vulnerabilities (1st time for free) at URL: \/Analytics| (scans deeper than SATAN or ISS) http://all.net:8080 ----------------- Read "Protection and Security on the Information Superhighway" -just released by Wiley and Sons- -- ----------------- \Management /\/| 216-686-0090 - PO Box 1480, Hudson, OH 44236 \ /\/ | Check out info-security heaven and test your system \/\ /\/ | for known vulnerabilities (1st time for free) at URL: \/Analytics| (scans deeper than SATAN or ISS) http://all.net:8080 ----------------- Read "Protection and Security on the Information Superhighway" -just released by Wiley and Sons-