Date: Sat, 20 Jan 2018 06:30:37 +0000
From: nullius <nullius@nym.zone>
To: Jefferson Carpenter <jeffersoncarpenter2@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <9bb96f6f0d4a9956def943ee3111d51b@nym.zone>
References: <58fa85b8-cba3-ee34-8c96-41c6c7bfbf9c@gmail.com>
	<374ee97c-dae9-786f-5fc6-6fb6920360cb@gmail.com>
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In-Reply-To: <374ee97c-dae9-786f-5fc6-6fb6920360cb@gmail.com>
Subject: Re: [bitcoin-dev] Upgrading PoW algorithm
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On 2018-01-17 at 22:31:52 +0000, Jefferson Carpenter=20
<jeffersoncarpenter2@gmail.com> wrote:
>Bitcoin's difficulty will be maxed out within about 400 years, by=20
>Moore's law.

On 2018-01-19 at 20:54:52 +0000, Jefferson Carpenter=20
<jeffersoncarpenter2@gmail.com> wrote:
>In other words, max difficulty for SHA256 might be significantly faster=20
>than forcing the first 256 bits of a SHA512 hash...

=E2=80=9CMoore=E2=80=99s law=E2=80=9D is not a law of nature.  Indeed, chip=
makers began bumping=20
up against the limitations of *actual* natural laws about 15=E2=80=9420 yea=
rs=20
ago.  That is why instead of increasing core clock, they play the tricks=20
which opened the way for Meltdown and Spectre.  Feature size, and thus=20
transistor counts, will soon enough run into physical limitations, too.

But the scenario you describe does not even require such a discussion.

2^256 work for brute force is on the order of 10^77 hashes.  For the=20
number of atoms in the observable universe, I=E2=80=99ve seen estimates ran=
ging=20
=66rom 10^78 to 10^82.  Thus, you are suggesting that within 400 years,=20
computers will be able to compute one hash for every myriad of atoms in=20
the observable universe=E2=80=94perhaps one hash for every *ten* atoms. =20
Moreover, you suggest that twenty-fourth century computers will do this=20
fast enough to meet Bitcoin=E2=80=99s ten-minute target rate.

Such a proposition bypasses science, leaps over science fiction, and=20
lands in the realm of religion.  Perhaps a deity could do this=E2=80=94usin=
g a=20
computer made of other than matter, powered by other than energy. =20
Humans will *never* be capable of such a feat:  Not now, and not in a=20
billion years.  Certainly not a mere four centuries hence!

(I do not here positively exclude the possibility, however slim, that=20
mathematical breakthroughs may yield a preimage attack on SHA-256 which=20
is significantly better than bruteforce.  I *do* positively declare it=20
impossible that Earth-beings will ever be capable of performing 2^256=20
work.  Or even 2^128 work, for that matter.)

--=20
nullius@nym.zone | PGP ECC: 0xC2E91CD74A4C57A105F6C21B5A00591B2F307E0C
Bitcoin: bc1qcash96s5jqppzsp8hy8swkggf7f6agex98an7h | (Segwit nested:
3NULL3ZCUXr7RDLxXeLPDMZDZYxuaYkCnG)  (PGP RSA: 0x36EBB4AB699A10EE)
=E2=80=9C=E2=80=98If you=E2=80=99re not doing anything wrong, you have noth=
ing to hide.=E2=80=99
No!  Because I do nothing wrong, I have nothing to show.=E2=80=9D =E2=80=94=
 nullius

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