phc-discussions - Re: [PHC] PHC: survey and benchmarks

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Message-ID: <20150401133354.GA12478@openwall.com>
Date: Wed, 1 Apr 2015 16:33:54 +0300
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] PHC: survey and benchmarks

Steve,

On Mon, Mar 23, 2015 at 09:33:28PM -0500, Steve Thomas wrote:
> Name       | t_cost for 2x | t_cost for 3x | t_cost for 4x | t_cost for 5x
> -----------+---------------+---------------+---------------+---------------
> Argon      | 2             | 3             | 4             | 5
> battcrypt  | 0             | 1             | 3             | -
> Catena     | 2             | 3             | 4             | 5
> Lyra2      | 2             | 3             | 4             | 5
> POMELO     | 1             | -             | 2             | -
> Pufferfish | -             | 0             | -             | 1
> yescrypt   | 3             | 4             | 5             | 6

For yescrypt it's t = 2 to have it perform 2x the number of read-writes
compared to the total number of blocks.  t = 0 means 4/3, t = 1 means
5/3, and t = 2 means 2.  Then it's just whole numbers.

So if I understood you right, all of the numbers for yescrypt in the
table above should be decreased by 1.

... or are you only counting memory accesses starting with the point
where the memory is filled, and not counting the initial accesses
during memory filling (which often involves reads of previously-written
blocks, and thus contributes to the attacker's area-time product too)?
If so, your table is correct (for yescrypt; I didn't verify the rest).

Alexander