From: Tim Ruffing <tim.ruffing@mmci•uni-saarland.de>
To: bitcoin-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] Properties of an ideal PoW algorithm & implementation
Date: Wed, 19 Apr 2017 13:08:15 +0200 [thread overview]
Message-ID: <1492600095.1934.1.camel@mmci.uni-saarland.de> (raw)
In-Reply-To: <CAAt2M1-LsEgBXhMpAn+JkBwA+Q7AwikiVFY6z0jEfj8dCCBUTw@mail.gmail.com>
On Tue, 2017-04-18 at 12:34 +0200, Natanael via bitcoin-dev wrote:
> To prove that an implementation is near optimal, you would show
> there's a minimum number of necessary transistor activations per
> computed hash, and that your implementation is within a reasonable
> range of that number.
I'm not an expert on lower bounds of algorithms but I think proving
such properties is basically out of reach for mankind currently.
>
> We also need to show that for a practical implementation you can't
> reuse much internal state (easiest way is "whitening" the block
> header, pre-hashing or having a slow hash with an initial whitening
> step of its own). This is to kill any ASICBOOST type optimization.
> Performance should be constant, not linear relative to input size.
Yes, a reasonable thing in practice seems to use a slower hash function
(or just iterating the hash function many times), see also this thread:
https://twitter.com/Ethan_Heilman/status/850015029189644288 .
PoW verification will still be fast enough. That's not the bottleneck
of block verification anyway.
Also, I don't agree that a PoW function should not rely on memory.
Memory-hard functions are the best we have currently.
Tim
next prev parent reply other threads:[~2017-04-19 11:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
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2017-04-18 10:34 ` Natanael
2017-04-18 19:14 ` praxeology_guy
2017-04-19 11:08 ` Tim Ruffing [this message]
2017-04-19 17:43 ` Bram Cohen
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