Return-Path: Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id C6CD3C0001 for ; Sat, 6 Mar 2021 04:44:49 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id ACC9060657 for ; Sat, 6 Mar 2021 04:44:49 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -1.499 X-Spam-Level: X-Spam-Status: No, score=-1.499 tagged_above=-999 required=5 tests=[BAYES_50=0.8, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 0fkRMeQLgZ6f for ; Sat, 6 Mar 2021 04:44:47 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by smtp3.osuosl.org (Postfix) with ESMTPS id 6087A60605 for ; Sat, 6 Mar 2021 04:44:47 +0000 (UTC) Received: from mail-il1-f181.google.com (mail-il1-f181.google.com [209.85.166.181]) (authenticated bits=0) (User authenticated as jlrubin@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 1264ijIv011080 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 5 Mar 2021 23:44:45 -0500 Received: by mail-il1-f181.google.com with SMTP id i18so3917693ilq.13 for ; Fri, 05 Mar 2021 20:44:45 -0800 (PST) X-Gm-Message-State: AOAM533jEVSskv0giHZ5q9/Ir+yuV5k/QQeLMIu1fRPz2uJoTSz52lsc BWuIcKicZpQf/1PeFrPaItjAwVEbCtpbnPSD59U= X-Google-Smtp-Source: ABdhPJzh44LHUa9018CgXZMtP85GAmuoiBqIE29le8VST4ZOJ9LDIedW3BaooL0E/6kaUYqmWQ0Eh0P+k+xLAB2EL9I= X-Received: by 2002:a05:6e02:1ca4:: with SMTP id x4mr11393261ill.58.1615005884987; Fri, 05 Mar 2021 20:44:44 -0800 (PST) MIME-Version: 1.0 References: <20210306034343.fhwrxmq6gbb2os5m@ganymede> In-Reply-To: <20210306034343.fhwrxmq6gbb2os5m@ganymede> From: Jeremy Date: Fri, 5 Mar 2021 20:44:33 -0800 X-Gmail-Original-Message-ID: Message-ID: To: "David A. Harding" , Bitcoin Protocol Discussion Content-Type: multipart/alternative; boundary="00000000000015bff705bcd6dcee" Subject: Re: [bitcoin-dev] Taproot activation proposal "Speedy Trial" X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 06 Mar 2021 04:44:49 -0000 --00000000000015bff705bcd6dcee Content-Type: text/plain; charset="UTF-8" Thank you for resurfacing and collating this concept. At this time I don't see major issues with this course of action and think it represents not only a reasonable compromise between all different perspectives, but also gives us an opportunity to learn more about less 'slow' yet safe consensus upgrades. In particular, I am very happy to see the earliest activation concept included. Best, Jeremy -- @JeremyRubin On Fri, Mar 5, 2021 at 7:44 PM David A. Harding via bitcoin-dev < bitcoin-dev@lists.linuxfoundation.org> wrote: > On the ##taproot-activation IRC channel, Russell O'Connor recently > proposed a modification of the "Let's see what happens" activation > proposal.[1] The idea received significant discussion and seemed > acceptable to several people who could not previously agree on a > proposal (although this doesn't necessarily make it their first > choice). The following is my attempt at a description. > > 1. Start soon: shortly after the release of software containing this > proposed activation logic, nodes will begin counting blocks towards > the 90% threshold required to lock in taproot.[2] > > 2. Stop soon: if the lockin threshold isn't reached within approximately > three months, the activation attempt fails. There is no mandatory > activation and everyone is encouraged to try again using different > activation parameters. > > 2. Delayed activation: in the happy occasion where the lockin threshold > is reached, taproot is guaranteed to eventually activate---but not > until approximately six months after signal tracking started. > > ## Example timeline > > (All dates approximate; see the section below about BIP9 vs BIP8.) > > - T+0: release of one or more full nodes with activation code > - T+14: signal tracking begins > - T+28: earliest possible lock in > - T+104: locked in by this date or need to try a different activation > process > - T+194: activation (if lockin occurred) > > ## Analysis > > The goal of Speedy Trial is to allow a taproot activation attempt to > either quickly succeed or quickly fail---without compromising safety in > either case. Details below: > > ### Mitigating the problems of early success > > New rules added in a soft fork need to be enforced by a large part of > the economy or there's a risk that a long chain of blocks breaking the > rules will be accepted by some users and rejected by others, causing a > chain split that can result in large direct losses to transaction > receivers and potentially even larger indirect losses to holders due to > reduced confidence in the safety of the Bitcoin system. > > One step developers have taken in the past to ensure widespread adoption > of new consensus rules is programming in a delay between the time software > with those rules is expected to be released and when the software starts > tracking which blocks signal for activation. For example: > > Soft fork | Release | Start | Delta > -----------------+------------+------------+---------- > BIP68 (v0.12.1) | 2016-04-15 | 2016-05-11 | 26 days > BIP141 (v0.13.1) | 2016-10-27 | 2016-11-18 | 24 days > > Sources: BitcoinCore.org, > https://gist.github.com/ajtowns/1c5e3b8bdead01124c04c45f01c817bc > > Speedy Trial replaces most of that upfront delay with a backend delay. > No matter how fast taproot's activation threshold is reached by miners, > there will be six months between the time signal tracking starts and when > nodes will begin enforcing taproot's rules. This gives the userbase even > more time to upgrade than if we had used the most recently proposed start > date for a BIP8 activation (~July 23rd).[2] > > ### Succeed, or fail fast > > The earlier version of this proposal was documented over 200 days ago[3] > and taproot's underlying code was merged into Bitcoin Core over 140 days > ago.[4] If we had started Speedy Trial at the time taproot > was merged (which is a bit unrealistic), we would've either be less than > two months away from having taproot or we would have moved on to the > next activation attempt over a month ago. > > Instead, we've debated at length and don't appear to be any closer to > what I think is a widely acceptable solution than when the mailing list > began discussing post-segwit activation schemes over a year ago.[5] I > think Speedy Trial is a way to generate fast progress that will either > end the debate (for now, if activation is successful) or give us some > actual data upon which to base future taproot activation proposals. > > Of course, for those who enjoy the debate, discussion can continue while > waiting for the results of Speedy Trial. > > ### Base activation protocol > > The idea can be implemented on top of either Bitcoin Core's existing > BIP9 code or its proposed BIP8 patchset.[6] > > - BIP9 uses two time-based[7] parameters, starttime and timeout. Using > these values plus a time-based parameter for the minimum activation > delay would give three months for miners to activate taproot, but some > of that time near the start or the end might not be usable due to > signals only being measured in full retarget periods. However, the > six month time for users to upgrade their node would be not be > affected by either slow or fast block production. > > BIP9 is already part of Bitcoin Core and I think the changes being > proposed would be relatively small, resulting in a small patch that > could be easy to review. > > - BIP8 uses two height-based parameters, startheight and timeoutheight. > Using height values would ensure miners had a certain number of > retarget periods (6) to lock in taproot and that there'd be a certain > number of blocks (about 24,000) until activation, although latest lock > in and expected activation could occur moderately earlier or later > than the estimated three and six months. > > BIP8 would likely be used if Speedy Trial fails, so it could be > advantageous to base this proposal on BIP8 so that we gain > experience running that code in production. > > For additional discussion about using times versus heights, see today's > log for ##taproot-activation.[11] > > ### Additional concerns > > - Encourages false signaling: false signaling is when miners signal > readiness to enforce rules that their nodes don't actually support. > This was partially responsible for a six-block reorg shortly after the > final BIP66 activation[8] and was found to still be a problem during > the BIP68 lockin period despite BIP9 being designed to avoid it.[9] > > Because Speedy Trial only gives miners a maximum of three months to > signal support for taproot, it may encourage such false signaling. If > taproot locks in as a result of their signaling but most of them fail > to upgrade by the activation date several months later, unprepared > miners could lose large amounts of money and users could see long > reorgs (with unupgraded nodes and SPV lite clients potentially losing > money). > > Compared to other activation proposals, I think the only difference is > Speedy Trial's short timeline. False signaling is possible with any > other proposal and the same problems can occur if miners fail to > upgrade for any mandatory activation. > > ### Additional advantages > > - No mandatory signaling: at no time are miners required to signal by > Speedy Trial. This includes no mandatory signaling during the > locked_in period(s), although such signaling will be encouraged (as it > was with BIP9[10]). > > - Party time: to a lesser degree, a benefit mentioned for flag day > activation may also apply here: we could get up to six months > advanced notice of taproot activation, allowing users, developers, and > organizations to prepare software, announcements, and celebrations for > that event. > > ## Implementation details and next steps > > Initial discussion about implementation may be found in today's > ##taproot-activation log.[11] If it appears Speedy Trial may have > traction, Russell O'Connor has offered to work on a patch against BIP8 > implementing it. > > ## Acknowledgments > > The original idea for a short-duration attempt was discussed in the > ##taproot-activation IRC channel last July and the revised idea saw > additional evaluation there this week. Despite growing frustration, > discussion has been overwhelmingly constructive, for which all the > contributors should be commended. Although this should not in any way > imply endorsement, I'm grateful for the review and comments on a draft > of this email by Adam Gibson, Andrew Chow, Anthony Towns, Chris Belcher, > Jeremy Rubin, Jonas Nick, Luke Dashjr, Michael Folkson, Russell > O'Connor, and IRC users maybehuman and proofofkeags > > ## Footnotes > > [1] > https://en.bitcoin.it/wiki/Taproot_activation_proposals#Let.E2.80.99s_see_what_happens.2C_BIP8.28false.2C_3m.29 > > [2] A threshold of 1,815/2,016 blocks (90%) in a single retarget period > seemed to have near-universal support during the 2021-02-16 IRC > meeting. See: > https://en.bitcoin.it/wiki/Taproot_activation_proposal_202102 > > [3] > https://en.bitcoin.it/w/index.php?title=Taproot_activation_proposals&oldid=68062 > > [4] https://github.com/bitcoin/bitcoin/pull/19953 > > [5] > https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2020-January/017547.html > > [6] https://github.com/bitcoin/bitcoin/pull/19573 > > [7] BIP9's times are based on the median of the past 11 blocks, which > usually trails UTC by about 90 minutes but which can trail behind > realtime significantly if miners are doing weird things. > > [8] https://en.bitcoin.it/wiki/July_2015_chain_forks > > [9] https://buildingbitcoin.org/bitcoin-core-dev/log-2016-06-21.html#l-32 > > [10] > https://github.com/bitcoin/bitcoin/blob/ed25cb58f605ba583c735f330482df0bf9348f3a/src/test/versionbits_tests.cpp#L337-L339 > > [11] http://gnusha.org/taproot-activation/2021-03-05.log > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > --00000000000015bff705bcd6dcee Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Thank you for resurfacing= and collating this concept.

At this time I don't see major issue= s with this course of action and think it represents not only a reasonable = compromise between all different perspectives, but also gives us an opportu= nity to learn more about less 'slow' yet safe consensus upgrades. I= n particular, I am very happy to see the earliest activation concept includ= ed.

Best,

Jeremy


On Fri, Mar 5, 2021 at 7:44 PM David A. Hardi= ng via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
On the ##taproot-activation IRC c= hannel, Russell O'Connor recently
proposed a modification of the "Let's see what happens" activ= ation
proposal.[1] The idea received significant discussion and seemed
acceptable to several people who could not previously agree on a
proposal (although this doesn't necessarily make it their first
choice).=C2=A0 The following is my attempt at a description.

1. Start soon: shortly after the release of software containing this
=C2=A0 =C2=A0proposed activation logic, nodes will begin counting blocks to= wards
=C2=A0 =C2=A0the 90% threshold required to lock in taproot.[2]

2. Stop soon: if the lockin threshold isn't reached within approximatel= y
=C2=A0 =C2=A0three months, the activation attempt fails.=C2=A0 There is no = mandatory
=C2=A0 =C2=A0activation and everyone is encouraged to try again using diffe= rent
=C2=A0 =C2=A0activation parameters.

2. Delayed activation: in the happy occasion where the lockin threshold
=C2=A0 =C2=A0is reached, taproot is guaranteed to eventually activate---but= not
=C2=A0 =C2=A0until approximately six months after signal tracking started.<= br>
## Example timeline

(All dates approximate; see the section below about BIP9 vs BIP8.)

- T+0: release of one or more full nodes with activation code
- T+14: signal tracking begins
- T+28: earliest possible lock in
- T+104: locked in by this date or need to try a different activation proce= ss
- T+194: activation (if lockin occurred)

## Analysis

The goal of Speedy Trial is to allow a taproot activation attempt to
either quickly succeed or quickly fail---without compromising safety in
either case.=C2=A0 Details below:

### Mitigating the problems of early success

New rules added in a soft fork need to be enforced by a large part of
the economy or there's a risk that a long chain of blocks breaking the<= br> rules will be accepted by some users and rejected by others, causing a
chain split that can result in large direct losses to transaction
receivers and potentially even larger indirect losses to holders due to
reduced confidence in the safety of the Bitcoin system.

One step developers have taken in the past to ensure widespread adoption of new consensus rules is programming in a delay between the time software<= br> with those rules is expected to be released and when the software starts tracking which blocks signal for activation.=C2=A0 For example:

=C2=A0 =C2=A0 Soft fork=C2=A0 =C2=A0 =C2=A0 =C2=A0 | Release=C2=A0 =C2=A0 |= Start=C2=A0 =C2=A0 =C2=A0 | Delta
=C2=A0 =C2=A0 -----------------+------------+------------+----------
=C2=A0 =C2=A0 BIP68 (v0.12.1)=C2=A0 | 2016-04-15 | 2016-05-11 | 26 days =C2=A0 =C2=A0 BIP141 (v0.13.1) | 2016-10-27 | 2016-11-18 | 24 days

=C2=A0 =C2=A0 Sources: BitcoinCore.org, https://gist.github.com/ajtowns/1c5e3b8bdead01124c04c45f01c817bc
Speedy Trial replaces most of that upfront delay with a backend delay.
No matter how fast taproot's activation threshold is reached by miners,=
there will be six months between the time signal tracking starts and when nodes will begin enforcing taproot's rules.=C2=A0 This gives the userba= se even
more time to upgrade than if we had used the most recently proposed start date for a BIP8 activation (~July 23rd).[2]

### Succeed, or fail fast

The earlier version of this proposal was documented over 200 days ago[3] and taproot's underlying code was merged into Bitcoin Core over 140 day= s
ago.[4]=C2=A0 If we had started Speedy Trial at the time taproot
was merged (which is a bit unrealistic), we would've either be less tha= n
two months away from having taproot or we would have moved on to the
next activation attempt over a month ago.

Instead, we've debated at length and don't appear to be any closer = to
what I think is a widely acceptable solution than when the mailing list
began discussing post-segwit activation schemes over a year ago.[5]=C2=A0 I=
think Speedy Trial is a way to generate fast progress that will either
end the debate (for now, if activation is successful) or give us some
actual data upon which to base future taproot activation proposals.

Of course, for those who enjoy the debate, discussion can continue while waiting for the results of Speedy Trial.

### Base activation protocol

The idea can be implemented on top of either Bitcoin Core's existing BIP9 code or its proposed BIP8 patchset.[6]

- BIP9 uses two time-based[7] parameters, starttime and timeout.=C2=A0 Usin= g
=C2=A0 these values plus a time-based parameter for the minimum activation<= br> =C2=A0 delay would give three months for miners to activate taproot, but so= me
=C2=A0 of that time near the start or the end might not be usable due to =C2=A0 signals only being measured in full retarget periods.=C2=A0 However,= the
=C2=A0 six month time for users to upgrade their node would be not be
=C2=A0 affected by either slow or fast block production.

=C2=A0 =C2=A0 BIP9 is already part of Bitcoin Core and I think the changes = being
=C2=A0 =C2=A0 proposed would be relatively small, resulting in a small patc= h that
=C2=A0 =C2=A0 could be easy to review.

- BIP8 uses two height-based parameters, startheight and timeoutheight.
=C2=A0 Using height values would ensure miners had a certain number of
=C2=A0 retarget periods (6) to lock in taproot and that there'd be a ce= rtain
=C2=A0 number of blocks (about 24,000) until activation, although latest lo= ck
=C2=A0 in and expected activation could occur moderately earlier or later =C2=A0 than the estimated three and six months.

=C2=A0 =C2=A0 BIP8 would likely be used if Speedy Trial fails, so it could = be
=C2=A0 =C2=A0 advantageous to base this proposal on BIP8 so that we gain =C2=A0 =C2=A0 experience running that code in production.

For additional discussion about using times versus heights, see today's=
log for ##taproot-activation.[11]

### Additional concerns

- Encourages false signaling: false signaling is when miners signal
=C2=A0 readiness to enforce rules that their nodes don't actually suppo= rt.
=C2=A0 This was partially responsible for a six-block reorg shortly after t= he
=C2=A0 final BIP66 activation[8] and was found to still be a problem during=
=C2=A0 the BIP68 lockin period despite BIP9 being designed to avoid it.[9]<= br>
=C2=A0 Because Speedy Trial only gives miners a maximum of three months to<= br> =C2=A0 signal support for taproot, it may encourage such false signaling.= =C2=A0 If
=C2=A0 taproot locks in as a result of their signaling but most of them fai= l
=C2=A0 to upgrade by the activation date several months later, unprepared =C2=A0 miners could lose large amounts of money and users could see long =C2=A0 reorgs (with unupgraded nodes and SPV lite clients potentially losin= g
=C2=A0 money).

=C2=A0 Compared to other activation proposals, I think the only difference = is
=C2=A0 Speedy Trial's short timeline.=C2=A0 False signaling is possible= with any
=C2=A0 other proposal and the same problems can occur if miners fail to
=C2=A0 upgrade for any mandatory activation.

### Additional advantages

- No mandatory signaling: at no time are miners required to signal by
=C2=A0 Speedy Trial.=C2=A0 This includes no mandatory signaling during the<= br> =C2=A0 locked_in period(s), although such signaling will be encouraged (as = it
=C2=A0 was with BIP9[10]).

- Party time: to a lesser degree, a benefit mentioned for flag day
=C2=A0 activation may also apply here: we could get up to six months
=C2=A0 advanced notice of taproot activation, allowing users, developers, a= nd
=C2=A0 organizations to prepare software, announcements, and celebrations f= or
=C2=A0 that event.

## Implementation details and next steps

Initial discussion about implementation may be found in today's
##taproot-activation log.[11] If it appears Speedy Trial may have
traction, Russell O'Connor has offered to work on a patch against BIP8<= br> implementing it.

## Acknowledgments

The original idea for a short-duration attempt was discussed in the
##taproot-activation IRC channel last July and the revised idea saw
additional evaluation there this week.=C2=A0 Despite growing frustration, discussion has been overwhelmingly constructive, for which all the
contributors should be commended.=C2=A0 Although this should not in any way=
imply endorsement, I'm grateful for the review and comments on a draft<= br> of this email by Adam Gibson, Andrew Chow, Anthony Towns, Chris Belcher, Jeremy Rubin, Jonas Nick, Luke Dashjr, Michael Folkson, Russell
O'Connor, and IRC users maybehuman and proofofkeags

## Footnotes

[1] https://en.bitcoin.it/wiki/Taproot_activation_proposals#Let.= E2.80.99s_see_what_happens.2C_BIP8.28false.2C_3m.29

[2] A threshold of 1,815/2,016 blocks (90%) in a single retarget period
=C2=A0 =C2=A0 seemed to have near-universal support during the 2021-02-16 I= RC
=C2=A0 =C2=A0 meeting.=C2=A0 See: https= ://en.bitcoin.it/wiki/Taproot_activation_proposal_202102

[3] https://= en.bitcoin.it/w/index.php?title=3DTaproot_activation_proposals&oldid=3D= 68062

[4] https://github.com/bitcoin/bitcoin/pull/19953
[5] https://lists.li= nuxfoundation.org/pipermail/bitcoin-dev/2020-January/017547.html

[6] https://github.com/bitcoin/bitcoin/pull/19573
[7] BIP9's times are based on the median of the past 11 blocks, which =C2=A0 =C2=A0 usually trails UTC by about 90 minutes but which can trail be= hind
=C2=A0 =C2=A0 realtime significantly if miners are doing weird things.

[8] https://en.bitcoin.it/wiki/July_2015_chain_forks=

[9] https://buildingbitcoin.org= /bitcoin-core-dev/log-2016-06-21.html#l-32

[10] https://github.com/bitcoin/bitcoin/blob/ed25cb58f= 605ba583c735f330482df0bf9348f3a/src/test/versionbits_tests.cpp#L337-L339

[11] http://gnusha.org/taproot-activation/2021-03= -05.log
_______________________________________________
bitcoin-dev mailing list
= bitcoin-dev@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mail= man/listinfo/bitcoin-dev
--00000000000015bff705bcd6dcee--