On Sun, Mar 2, 2014 at 6:54 AM, Christian Heimes <christ...@python.org> wrote: > Yes, for most applications brute force is still the best option to crack > the password. Passwords are usually rather short, have a low entropy and > modern hardware is insanely fast. With software like [1] and a fast GPU > it is possible to do more than 10*10^9 checks/second for SHA-256.
Using XKCD 936's estimate, 44 bits of entropy would still require 17592 seconds of processing at 10^9 per second. That's not a lot if someone's personally targeting you *and* they know you use XKCD 936 *and* know the exact set of 2048 words that you drew your password from *and* they know how you lay them out (spaces between, no spaces, whether or not you capitalize the words, etc etc). Not knowing any of these would add a few more bits of entropy; and if you use /usr/share/dict/words and take only those words which consist entirely of lower-case letters, then your corpus is over 65536 words [1], so you have 64 bits of entropy. Even at 10^10 checks/second (which is what 10*10^9 is, but that's an odd way to write it), that would be 21350 *days* of dedicated processing, just to crack the one password. If cracking my password, and mine alone, in sixty years, is considered "insanely fast", then I'm going to keep using SHA-256 for a while. The problem isn't SHA-256. The problem is insecure passwords, the way we've been taught to make them by the banks. Hence, XKCD 936. ChrisA [1] On my Debian Wheezy system: $ grep -c '^[a-z]*$' /usr/share/dict/words 72861 -- https://mail.python.org/mailman/listinfo/python-list
