phc-discussions - Re: [PHC] Re: Attack on Argon2i?

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Message-ID: <823150416.20160112184402@gmail.com>
Date: Tue, 12 Jan 2016 18:44:02 +0100
From: Krisztián Pintér <pinterkr@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Re: Attack on Argon2i?

Bill Cox (at Tuesday, January 12, 2016, 6:30:07 PM):

> ./argon2memtest $((1 << 26))
> Max blocks used 12409040 out of 67108864.  Memory reduction 5.41X

i don't recall if i posted this to the list, but if not, i swear i'm
not making this up after this article :)

so i'm long since against pseudorandom but fix access patterns. first,
i don't see the benefit of a pseudorandom but fixed over a simple and
fixed. it is still fixed. second, i see the risk that anything chosen
randomly might be suboptimal. especially if it depends on a value
(like salt) out of control. i don't like their approach for the same
reason.

analogy: s-boxes. it is known, that random s-boxes are suboptimal in
comparison to carefully crafted ones. this is the expected thing,
since why would a random object be optimal? it only happens if the
vast majority of possible objects are optimal, which at least needs a
proof.

this is why i like catena's more scientific approach, or yes, my own
for that matter.