phc-discussions - Re: [PHC] yescrypt to gain Catena features (Re: [PHC] gambit wiki strength)

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Message-ID: <alpine.DEB.2.10.1404161156070.16019@debian>
Date: Wed, 16 Apr 2014 12:07:50 +0200 (CEST)
From: Stefan.Lucks@...-weimar.de
To: discussions@...sword-hashing.net
Subject: Re: [PHC] yescrypt to gain Catena features (Re: [PHC] gambit wiki
 strength)

On Tue, 15 Apr 2014, Bill Cox wrote:

> > You are invited to use the Catena framework with other algorithms of
> > your choice!
> 
> I just might!  I could also enhance it to provide an outer t_cost-like
> loop that repeats hashes without increasing garlic.

We had considered this for Catena. But to support client-independent 
updates, you'd need to remember which parameter you did increase when. If, 
historically, you did first increase the memory, update the hash, and 
later you did increase the number of iterations, updating the hash again, 
then you get a different password hash than if you first increase the 
number of iterations and then increase the memory.

For that reason, Catena proposes the usage of pepper (i.e., keep some of 
the salt bits secret) to slow down password hashing without increasing the 
memory.

> Honestly, I think a good common API might be one of the best things to
> come out of the PHC.  Improved PHS's are awesome, but improving usability
> for the user could be just as important.  If the PHC committee is
> interested in exploring such an API, I'd love to be involved.

Well, "one of the best things" is a bit strong.

But in any case, an API that would equally support different PHC 
candidates (ideally, all finalists), and which thus would allow to change 
the password scrambler without much work beyond changing one line in the 
source code and then recompiling, would be cool, indeed.

So long

Stefan

------  I  love  the  taste  of  Cryptanalysis  in  the morning!  ------
     <http://www.uni-weimar.de/cms/medien/mediensicherheit/home.html>
--Stefan.Lucks (at) uni-weimar.de, Bauhaus-Universität Weimar, Germany--