phc-discussions - Re: [PHC] blakerypt sequential memory-hard function

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Date: Mon, 9 Dec 2013 20:30:18 +0100
From: Krisztián Pintér <pinterkr@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] blakerypt sequential memory-hard function

Stefan.Lucks@...-weimar.de (at Monday, December 9, 2013, 1:54:41 PM):

> You know Boyen's halting password puzzles (for time usage, not really for
> memory usage)?

> https://crypto.stanford.edu/~xb/security07/index.html

that is very interesting with two remarks:

1. this design uses indexing on secret. also, i'm not exactly a math
person, but it appears to me that it is essential to the proof. if i'm
not mistaken, basically it is a walk based on the secret, without
which you "get lost in the forest". i wonder if you can circumvent
this limitation.

2. though a good initiative, its benefits are not as huge as it first
seems. we can't expect users to be very sophisticated with their
choice of parameters. to be user friendly, you probably want to offer
some preset values, and not just run-till-stopped. and therefore we
can kind of expect the running time to be guessable. it is also easy
to listen in on an authentication session, and measure the timing.