[ale] OT - New encryption technology using a piece of paper

[Derek Atkins]

Michael Trausch <mike at trausch.us> writes:

> On 09/06/2011 11:30 AM, Drifter wrote:
>> Can't the industry put a halt to brute force attempts at password cracking 
>> simply by instituting an ever-increasing delay following incorrect 
>> password input?
>
> It doesn't even need to be ever-increasing; constant is acceptable, so
> long as it is built-in.
>
> One reason I don't consider a site to be secure unless there is a KDF
> involved that requires at least 0.1 seconds of CPU time per each
> password attempt.  That means that not only is a password entity
> protected over the network by way of brute force, but it is also
> protected if the database itself, which stores the key that is derived
> from the password (and I should hope, the salt) is ever stolen.

The downside is that the longer it takes to compute the key the more you
can perform a DoS against the server by having it perform KDF functions.
This is particularly a problem if the server has to perform
significantly more work than the client.  For example, the client could
connect, submit the attempt, and then disconnect and reconnect again to
get the server to expend lots of useless effort.

Also, there are potentially offline dictionary attacks depending on the
system in use.

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available