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Date: Mon, 01 Apr 2024 13:32:23 +0000
To: Andrew Poelstra <apoelstra@wpsoftware.net>
From: "'Fabian' via Bitcoin Development Mailing List" <bitcoindev@googlegroups.com>
Cc: Jameson Lopp <jameson.lopp@gmail.com>, bitcoindev@googlegroups.com
Subject: Re: [bitcoindev] The Future of Bitcoin Testnet
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Hi all,

I second that Signet is not a replacement for Testnet.

Softforking in the fix is definitely possible and worth considering if too =
many projects complain about the hassle of changing to a testnet4. However,=
 this alone doesn't help with any of the other issues OP mentioned.

Getting rid of the halving for testnet3 doesn't seem like a good idea to me=
 since this would mean all projects that have some kind of unintended infla=
tion detection would need to add exceptions. This seems like a much larger =
engineering effort than simply switching to a testnet4. Beyond that, I agre=
e with previous posters that there is value in keeping testnet as close to =
mainnet as possible. Also, we would be locking in an already very low subsi=
dy in testnet3.

So far, I think the reset together with a fix for the difficulty adjustment=
 is the best solution and hopefully discourages scammers from building on B=
itcoin testnets. Maybe we should even get into the habit and just reset wit=
h every halving. FWIW, I have created a draft PR with a difficulty adjustme=
nt fix and some initial work for a testnet4: https://github.com/bitcoin/bit=
coin/pull/29775

Side note: I think one of the main causes for the insufficient distribution=
 of testnet/signet coins is that building and running a faucet that works a=
s intended robustly, withstands attacks etc. is a very hard problem. If we =
had such a system that just works (TM) and will be maintained long-term, I =
think there would be more people willing to donate their testnet coins to s=
uch a system. Maybe this is a project worthy of some OS funding.

Best,
Fabian


On Monday, April 1st, 2024 at 3:25 PM, Andrew Poelstra <apoelstra@wpsoftwar=
e.net> wrote:

> On Sun, Mar 31, 2024 at 09:19:50AM -0400, Jameson Lopp wrote:
>=20
> > 2. The reason the block height is insanely high is due to a rather amus=
ing
> > edge case bug that causes the difficulty to regularly get reset to 1, w=
hich
> > causes a bit of havoc. If you want a deep dive into the quirk:
> > https://blog.lopp.net/the-block-storms-of-bitcoins-testnet/
>=20
>=20
> The purpose of this is to avoid situations where a single miner drives
> the difficulty way up and then drops off, leaving the other testnet
> miners unable to produce blocks. In the early CPU->GPU->FPGA->ASIC days
>=20
> it could happen that there was only one person with an ASIC who would
> have literally a 1000x advantage over other miners (since miner costs
> money and nobody gets paid).
>=20
> Nowadays we can probably assume that anyone who cares to mine testnet
> can scrounge up a couple used S9s or something, so for a griefer to
> obtain a 1000x advantage like this would require a serious cash
> investment. So maybe it's okay to drop the rule entirely.
>=20
> But I would propose weakening it -- requiring no blocks for a longer
> period of time and resetting the difficulty to something (much) higher
> than 1. Or just dropping the difficulty by a fixed factor of 128 or
> something (though we'd need extra logic to avoid this being done
> repeatedly to drive the difficulty to 1 anyway, maybe) so we don't
> need to guess at a reasonable floor.
>=20
> Obviously this is a major bikeshedding vector but hopefully people don't
> get too enthusiastic about particular values here. Just pick something
> and run with it.
>=20
> Anyway ACK resetting testnet if people are valuing its coins. I recall
> a long time ago this was (in some sense I don't remember) an official
> condition under which testnet was supposed to be reset.
>=20
>=20
> --
> Andrew Poelstra
> Director of Research, Blockstream
> Email: apoelstra at wpsoftware.net
> Web: https://www.wpsoftware.net/andrew
>=20
> The sun is always shining in space
> -Justin Lewis-Webster
>=20
> --
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