phc-discussions - Re: [PHC] A final cheat killer pass with smoke

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Message-ID: <2751.1389256327@critter.freebsd.dk>
Date: Thu, 09 Jan 2014 08:32:07 +0000
From: "Poul-Henning Kamp" <phk@....freebsd.dk>
To: discussions@...sword-hashing.net, Bill Cox <waywardgeek@...il.com>
Subject: Re: [PHC] A final cheat killer pass with smoke

In message <CAOLP8p7id+0+o5pArhYSKL6Hx1VuUhNOJ3R9EG5_wkJ5O4_X1A@...l.gmail.com>
, Bill Cox writes:
>--001a11c2aa6a36e0f704ef7fa399
>Content-Type: text/plain; charset=ISO-8859-1
>
>That's what the "smoke" is for.  If all an attacker has access to is cache
>miss timing, then simply randomizing the order of of memory access would
>make it virtually impossible to gain information from the timing.

Can I mention another thing which bugs me, now that I've got started ?

The word "random" is not in our dictionary.

We have three parts to work with:

The password, which contains entropy, but which is not random, certainly
not from invocation to invocation.

Salt(s), that can be random, or more likely least pseudo-random,
but we should assume that the attacker knows it.

The algorithm, which is deterministic[1], and which the attacker also
know -- and can optimize.

Please use the word "random" sparesly, most of the time it is unwarranted.

Poul-Henning

[1] I'm personally willing to entertain probablistic algorithms,
    but I can't speak for everybody else.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@...eBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.