Re: Strengthening the Passphrase Model (was Re: PGP compromised on Windows 9x?)

[Rodney Thayer]

At 09:46 AM 2/9/99 -0500, Arnold G. Reinhold wrote:
>Nelson Minar's comments (reproduced below) are right on target. Here are
[...] practical suggestions [...]

>2. PGP should burn computer time hashing the passphrase. While you cannot
>increase the entropy of a passphrase with an algorithm, you can make
>exhaustive search far more difficult.

There was an interesting paper presented last week at NDSS '99
(http://www.isoc.org/ndss99) by Ari Juels and John Brainard, called "Client
Puzzles", which relates.  The notion is to cause the user to burn a bit of
compute time solving a puzzle, in the interest of preventing certain kinds
of attacks.