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From: Andrew Poelstra <apoelstra@wpsoftware•net>
Subject: Re: [bitcoindev] The Future of Bitcoin Testnet
Date: Mon, 1 Apr 2024 14:20:53 +0000	[thread overview]
Message-ID: <ZgrCxWxMkiAt2Tg2@camus> (raw)
In-Reply-To: <>

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On Mon, Apr 01, 2024 at 01:37:59PM +0000, Pieter Wuille wrote:
> As for using other measures to prevent too large difficulty variations... I'm not sure that's desirable, because it always cuts both ways (nicely demonstrated by the "allow difficulty 1 rule" on testnet3 backfiring and enabling block storms!). For applications that actually need very predictable block rate, there is signet. For others, just the normal mainnet rules are probably not too terrible. I would be ok with having a somewhat reduced block interval (say a few days instead of 2 weeks) if that's not deemed to complex to implement across the ecosystem, but I don't think it's that important.

I really like this. For my part (rust-bitcoin) this would be as simple
as adding an extra parameter to my blockparams structure. Possibly one
already exists, I'd have to check.

This would be much easier than the existing situation where we have
special-case logic for testnet the difficulty-1 target.

It would also limit the amount of bikeshedding possible, since there
aren't too many conflicting goals regarding the retargeting window...
unlike tweaking the existing logic where there's a tradeoff between
"we should make this never happen" and "it should happen often enough
that it doesn't break people's code" and "it should happen if blocks
slow down to like, 1/50th their normal rate even if they are still
technically being produced" and "it shouldn't be possible to trigger
it within the 2-hour timestamp-faking window" etc. And questions
about whether we should fix/redesign the interaction between the reset
rule and the normal difficulty retarget.

OTOH, since we already have the special logic, I'd also be happy with
tweaking the existing rule. My specific proposal (after reading Jameson's
post, which has some nice graphs of difficulty) would be

* increase the reset threshold from 20 minutes to 6 hours, which is
  (a) well outside the 2-hour window in which miners can easily fake
  timestamps, and (b) will basically never be hit by accident
* increase the reset difficulty from 1 to 1MM, which is an rough lower
  bound on the "normal" testnet difficulty seen historically

Which puts us in the "this rule would never be triggered unless
literally everyone stopped mining" corner of the design space.

Andrew Poelstra
Director of Research, Blockstream
Email: apoelstra at

The sun is always shining in space
    -Justin Lewis-Webster

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  reply	other threads:[~2024-04-01 14:21 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-31 13:19 Jameson Lopp
2024-03-31 14:33 ` Luke Dashjr
2024-03-31 14:57   ` Jameson Lopp
2024-03-31 17:21     ` Eric Voskuil
2024-04-09 18:28   ` Garlo Nicon
2024-03-31 16:02 ` Peter Todd
2024-03-31 21:01   ` Nagaev Boris
2024-03-31 21:29     ` Peter Todd
2024-04-01 12:54       ` Jameson Lopp
2024-04-01 13:37         ` Pieter Wuille
2024-04-01 14:20           ` Andrew Poelstra [this message]
2024-04-01 22:01             ` 'Fabian' via Bitcoin Development Mailing List
2024-04-02 11:53               ` Jameson Lopp
2024-04-02 18:36                 ` Lukáš Kráľ
2024-04-02 19:46                   ` Jameson Lopp
2024-04-03  4:19           ` Anthony Towns
2024-04-03 18:18             ` emsit
2024-04-03 19:35               ` Andrew Poelstra
2024-04-30 18:46               ` Matthew Bagazinski
2024-05-01 15:30                 ` Garlo Nicon
2024-05-04 17:13                 ` Peter Todd
2024-04-10  6:57       ` Garlo Nicon
2024-04-22  4:33         ` Ali Sherief
2024-04-01 13:25 ` Andrew Poelstra
2024-04-01 13:32   ` 'Fabian' via Bitcoin Development Mailing List
2024-04-01 14:28 ` Warren Togami
2024-04-01 19:22 ` [bitcoindev] " emsit
2024-04-04  8:14 ` Calvin Kim
2024-04-04 12:47   ` Jameson Lopp
2024-04-05  4:30     ` Calvin Kim
2024-04-06 23:04       ` David A. Harding
2024-04-09 16:48         ` Peter Todd
2024-04-16 17:30           ` [bitcoindev] " 'Sjors Provoost' via Bitcoin Development Mailing List
2024-04-07  7:20   ` [bitcoindev] " Christian Decker
2024-04-07  8:09     ` K Calvin
2024-04-08 19:11 ` Garlo Nicon
2024-04-09  4:29   ` coinableS
2024-04-28 13:45 ` [bitcoindev] " Matt Corallo
2024-05-02  7:10   ` Ali Sherief
2024-05-04 17:08     ` Peter Todd

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