Re: scrypt time-memory tradeoff

[Solar Designer <solar@openwall.com>]

On Sun, Nov 18, 2012 at 03:23:31AM -0800, Colin Percival wrote:
> You get a 2x cost reduction by trading increased time for reduced area (as
> in a previous email) and another 2x reduction by ignoring the initial setup
> (practically speaking)

Yes, that's what I was thinking.  The initial setup time becomes
negligible compared to that of the second phase - or it can even be
fully removed, but that's not optimal in practice because the Salsa20
core has some area cost too.

> but I never intended to include the setup in my
> area-time bound.

Oh, that's nice.

In other words, you could have killed this trade-off (by slightly
different design) and then claim 4x or 2x higher costs (depending on
whether the trade-off was accounted for in the costs or not).

Alexander