Date: Tue, 18 May 2021 12:58:19 +0000
To: ZmnSCPxj <ZmnSCPxj@protonmail.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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Cc: marshall ball <marshallball@gmail.com>
Subject: Re: [bitcoin-dev] Proposal: Low Energy Bitcoin PoW
Precedence: list

Good morning Michael,

> Good morning Michael,
>
> > Nothing in a dynamic system like PoW mining can be 100% anticipated, fo=
r example there might be advanced in manufacturing of chips which are paten=
ted and so on.
> > It sounds like your take is that this means no improvements can ever be=
 made by any mechanism, however conservative.
>
> Not at all.
>
> Small-enough improvements over long-enough periods of time are expected a=
nd anticipated --- that is why there exists a difficulty adjustment mechani=
sm.
> What is risky if a large-enough improvement over a short-enough time that=
 overwhelms the difficulty adjustment mechanism.
> ASICBOOST was a massive enough improvement that it could be argued to pot=
entially overwhelm this mechanism if it was not openly allowed for all mine=
rs.

Or to put it in another perspective:

* Small improvements to PoW mining are tolerated by Bitcoin.
  * Such improvements are expected to be common.
* Large improvements to PoW mining are potential extinction events for Bitc=
oin, due to massive centralization risk.
  * Such improvements are expected to be *rare* but *not* nonexistent.
* The number of possible circuit configurations is bounded by physical limi=
ts (matter is quantized, excssively-large chips are infeasible, etc.), thus=
 the number of expected optimizations of a particular overall algorithm are=
 bounded.

Suppose two manufacturers find two different small improvements to PoW mini=
ng.
In all likelihood, "the sum is better than its parts" and if the two have a=
 cross-licensing deal, they can outcompete their *other* competition.
Further, even if some small competitor violates the patent, the improvement=
 may be small enough that the patent owner may decide the competitor is too=
 small to bother with all the legal fees involved to enforce the patent.
Thus, small improvements to PoW mining are expected to eventually spread wi=
dely, and that is what the difficulty adjustment mechanism exists to modula=
te.

But suppose a third manufacturer develops an ASICBOOST-level optimization o=
f whatever the PoW mining algorithm is.
That manufacturer has no incentive to cross-license, since it can dominate =
the competition without cross-licensing a bunch of smaller optimizations (t=
hat may not even add up to compete against the ASICBOOST-level optimization=
).
And any small competitor that violates patent will be enforced against, due=
 to the major improvement that the large optimization has and the massive m=
onopolistic advantage the ASICBOOST-level optimization patent holder would =
have.


SHA256d-on-Bitcoin-block-header has already uncovered ASICBOOST, and thus t=
he number of possible other large optimizations is that much smaller --- th=
e number of possible optimizations is bounded by physical constraints.
Thus, the risk of a black-swan event where a new optimization of SHA256d-on=
-Bitcoin-block-header is large enough to massively centralize mining is red=
uced, compared to every other alternative PoW algorithm, which is an import=
ant reason to avoid changing PoW as much as possible, without some really s=
erious study (which you might be engaged in --- I am not enough of a mathis=
t to follow your papers).

We are more likely to want to change SHA256 for SHA3 on the txid and Merkle=
 trees than on the PoW.


Regards,
ZmnSCPxj