Subject: Re: [bitcoin-dev] BIP proposal: Reserved nversion bits in blockheader

From: Luke Dashjr <[email-masked]>
Date: Wed, 7 Mar 2018 14:43:11 +0000

Why are you posting this obsolete draft? You've already received review in 
private, and been given useful suggestions. There's even a shared Google Doc 
with the current draft:

    https://docs.google.com/document/d/1GedKia78NUAtylCzeRD3lMlLrpPVBFg9TV9LRqvStak/edit?usp=sharing

Again:

* This is no different from what Timo and Sergio proposed years ago, and as 
such should be based on their work instead of outright not-invented-here 
respecification. The current draft integrates their work while not trying to 
steal credit for it (they are included as primary authors).

* The specification should be complete, including updates for GBT and the 
Stratum mining protocol. These are included in the current draft.

Additionally, it is not appropriate to begin using a draft BIP on mainnet 
before any discussion or consensus has been reached. Doing so seems quite 
malicious, in fact. I hope DragonMint miners can still operate using the 
*current* Bitcoin protocol.

Luke

On Wednesday 07 March 2018 8:19:57 AM Btc Drak via bitcoin-dev wrote:
> Hi,
> 
> The following proposal reduces the number of version-bits that can be used
> for parallel soft-fork signalling, reserving 16 bits for non-specific use.
> This would reduce the number of parallel soft-fork activations using
> versionbits to from 29 to 13 and prevent node software from emitting false
> warnings about unknown signalling bits under the versionbits signalling
> system (BIP8/9). I chose the upper bits of the nVersion, because looking at
> the versionbits implementation in the most widely deployed node software,
> it is easier to implement than say annexing the lower 2 bytes of the field.
> 
> The scope of the BIP is deliberately limited to reserving bits for general
> use without specifying specific uses for each bit, although there have
> previously been various discussions of some use-cases of nVersion bits
> including version-rolling AsicBoost[1], and nonce rolling to reduce CPU
> load on mining controllers because ntime-rolling can only be done for short
> periods otherwise it could have negative side effects distorting time.
> However, specific use cases are not important for this BIP.
> 
> I am reviving discussion on this topic now, specifically, because the new
> DragonMint miner uses version-rolling AsicBoost on mainnet[2]. It is
> important to bring up so node software can adapt the versionbits warning
> system to prevent false positives. This BIP has the added advantage that
> when a new use for bits is found, mining manufacturers can play in the
> designated area without causing disruption or inconvenience (as
> unfortuntely, the use of version-rolling will cause until BIP8/9 warning
> systems are adapted). I appologise for the inconvenience in advance, but
> this is the unfortunate result of restraints while negotiating to get the
> patent opened[3] and licensed defensively[4] in the first place.
> 
> I believe there was a similar proposal[5] made some years ago, before the
> advent of BIP9. This proposal differs in that it's primary purpose is to
> remove bits from the versionbits soft-fork activation system and earmark 16
> bits for general use without allocating fixed uses for each bit. The BIP
> cites a couple of usecases for good measure, but they are just
> informational examples, not part of a specification laid down. For this
> reason, there no is mention of the version-rolling Stratum extension[6]
> specifics within the BIP text other than a reference to the specification
> itself.
> 
> Refs:
> 
> [1] https://arxiv.org/pdf/1604.00575.pdf
> [2]
> https://halongmining.com/blog/2018/03/07/dragonmint-btc-miner-uses-version-> rolling-asicboost/ [3]
> https://www.asicboost.com/single-post/2018/03/01/opening-asicboost-for-defe
> nsive-use/ [4] https://blockchaindpl.org/
> [5] https://github.com/BlockheaderNonce2/bitcoin/wiki
> [6] http://stratumprotocol.org/stratum-extensions
> 
> <pre>
>   BIP: ?
>   Title: Reserved nversion bits in blockheader
>   Author: BtcDrak <[email-masked]>
>   Comments-Summary: No comments yet.
>   Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-????
>   Status: Draft
>   Type: Informational
>   Created: 2018-03-01
>   License: BSD-3-Clause
>            CC0-1.0
> </pre>
> 
> ==Abstract==
> 
> This BIP reserves 16 bits of the block header nVersion field for
> general purpose use and removes their meaning for the purpose of
> version bits soft-fork signalling.
> 
> ==Motivation==
> 
> There are a variety of things that miners may desire to use some of
> the nVersion field bits for. However, due to their use to coordinate
> miner activated soft-forks, full node software will generate false
> warnings about unknown soft forks if those bits are used for non soft
> fork signalling purposes. By reserving bits from the nVersion field
> for general use, node software can be updated to ignore those bits and
> therefore will not emit false warnings. Reserving 16 bits for general
> use leaves enough for 13 parallel soft-forks using version bits.
> 
> ==Example Uses==
> 
> The following are example cases that would benefit from using some of
> the bits from the nVersion field. This list is not exhaustive.
> 
> Bitcoin mining hardware currently can exhaust the 32 bit nonce field
> in less than 200ms requiring the controller to distribute new jobs
> very frequently to each mining chip consuming a lot of bandwidth and
> CPU time. This can be greatly reduced by rolling more bits. Rolling
> too many bits from nTime is not ideal because it may distort the
> timestamps over a longer period.
> 
> Version-rolling AsicBoost requires two bits from the nVersion field to
> calculate 4-way collisions. Any two bits can be used and mining
> equipment can negotiate which bits are to be used with mining pools
> via the Stratum "version-rolling" extension.
> 
> ==Specification==
> 
> Sixteen bits from the block header nVersion field, starting from 13
> and ending at 28 inclusive (0x1fffe000), are reserved for general use
> and removed from BIP8 and BIP9 specifications. A mask of 0xe0001fff
> should be applied to nVersion bits so bits 13-28 inclusive will be
> ignored for soft-fork signalling and unknown soft-fork warnings.
> 
> This specification does not reserve specific bits for specific purposes.
> 
> ==Backwards Compatibility==
> 
> This proposal is backwards compatible, and does not require a soft
> fork to implement.
> 
> ==References==
> 
> [[bip-0008.mediawiki|BIP8]]
> [[bip-0009.mediawiki|BIP9]]
> [https://arxiv.org/pdf/1604.00575.pdf AsicBoost white paper]
> [https://github.com/BlockheaderNonce2/bitcoin/wiki nNonce2 proposal]
> [http://stratumprotocol.org/ Stratum protocol extension for
> version-rolling]
> 
> ==Copyright==
> 
> This document is dual licensed as BSD 3-clause, and Creative Commons
> CC0 1.0 Universal.