Firewall Wizards mailing list archives
Re: password aging
From: Steve Bellovin <smb () research att com>
Date: Wed, 19 Aug 1998 11:40:11 -0400
In message <19980818175723.A4608 () weathership homeport org>, Adam Shostack write s:
Various people assert that its a good idea to maintain a history of user passwords so that they can't change their password to a previous password. However, I'm having trouble finding a reference to this in the literature that examines the issue of how many passwords to save and why. The lime green book (password management) says not to let the user use their previous password, but doesn't go into storing a history. Does anyone know of a paper on, or that discusses, this topic, and how or why to pick various values of N?
There are several rationales; most boil down to combatting user unwillingness to change their passwords. If forced to, they'll change it, then change it right back to the old one, and (often) iterate as needed. Another rationale is that if it takes a long time to crack a given password, but that pasword will be reused -- as is not unlikely -- one can try the old-but-recovered one every month or so, to see if it now works. I seem to recall some discussion of this topic in: @article{opus, author = {Eugene H. Spafford}, title = {{OPUS}: Preventing Weak Password Choices}, journal = {Computers \& Security}, volume = 11, number = 3, year = 1992, pages = {273--278}, annote = "Discusses how to use Bloom filters to check passwords against dictionaries without consuming large amounts of space.", url = {ftp://coast.cs.purdue.edu/pub/Purdue/papers/spafford/spaf-OPUS.ps} }
Current thread:
- password aging Adam Shostack (Aug 19)
- Re: password aging Rick Smith (Aug 23)
- <Possible follow-ups>
- Re: password aging Steve Bellovin (Aug 19)
- Re: password aging R. DuFresne (Aug 23)
- Re:password aging Harvey Nusz (Aug 19)
- Re: password aging HASSAN . KARIM (Aug 19)
- Re: password aging H. Morrow Long (Aug 23)
- Re: password aging Adam Shostack (Aug 24)
- Re: password aging Paul M. Cardon (Aug 26)
- Re: password aging Stephen P. Gibbons (Aug 27)
- Re: password aging Massimo Brogioni (Aug 27)
- Re: password aging John McDermott (Aug 24)
- Re: password aging Paul McNabb (Aug 28)
(Thread continues...)