Strong Web Passwords
Interesting paper from HotSec ’07: “Do Strong Web Passwords Accomplish Anything?” by Dinei Florêncio, Cormac Herley, and Baris Coskun.
ABSTRACT: We find that traditional password advice given to users is somewhat dated. Strong passwords do nothing to protect online users from password stealing attacks such as phishing and keylogging, and yet they place considerable burden on users. Passwords that are too weak of course invite brute-force attacks. However, we find that relatively weak passwords, about 20 bits or so, are sufficient to make brute-force attacks on a single account unrealistic so long as a “three strikes” type rule is in place. Above that minimum it appears that increasing password strength does little to address any real threat If a larger credential space is needed it appears better to increase the strength of the user ID’s rather than the passwords. For large institutions this is just as effective in deterring bulk guessing attacks and is a great deal better for users. For small institutions there appears little reason to require strong passwords for online accounts.
JRR • July 13, 2009 6:31 AM
I actually use acronym-based passwords, which I think are pretty strong.
The thing that I think is the most inadvertently detrimental to password strength is the requirement to change passwords every X days. If I can use the same password for a long time, I pick pretty strong passwords. If I have to change it every XX days, I tend to pick very easy to remember passwords, and just change a digit at the end of it every time. As a result of this password “enhancement” system, I think I personally have much weaker passwords.