Greg, I'd like to ask you to assign a BIP number to this proposal and open another round of discussion.
There is now a reference implementation available as pull request #5102 (https://github.com/bitcoin/bitcoin/pull/5102). It introduces a new version number (3) to properly distinguish the interpretation of the version number and allow for a clean upgrade process. Unittests are included. The updated BIP draft in .mediawiki format is available here: https://github.com/BlockheaderNonce2/bitoin/wiki Thanks, Timo On Sun, May 04, 2014 at 05:26:06PM +0200, Mike Hearn wrote: > Although I agree 32 bits for a version is overkill, I really don't like the > idea of you simply ignoring the protocol spec to try and reduce your own > costs. > Especially because in future we should make unknown versions a validation > rule, > so we can easily trigger hard forks. > > If this change was introduced through a proper process and software was > properly upgraded to understand the new header format, that'd be one thing. > Arbitrarily exploiting what is IMHO a missing rule in the rule set to shave a > bit more profit is something else. > > > On Sun, May 4, 2014 at 5:14 PM, Timo Hanke <timo.ha...@web.de> wrote: > > > If changing the structure of the block header, wouldnt you also need to > > increment the version number to 3? > > No, in this case I don't think so. Incrementing the version number has > two purposes: > > 1. inform old clients that something new is going on > 2. be able to phase out old version numbers and block them once the new > version number becomes a supermajority. > > None of these two is necessary here. Old clients already recognize the > new block headers as something new because they look like very high > version numbers to them. And there is no reason to ever phase out blocks > that have zero in the MSBs of the version. > > On Sun, Apr 27, 2014 at 10:17:11AM +0200, Melvin Carvalho wrote: > > On 27 April 2014 09:07, Timo Hanke <timo.ha...@web.de> wrote: > > > > I'd like to put the following draft of a BIP up for discussion. > > > > Timo > > > > # Abstract > > There are incentives for miners to find cheap, non-standard ways to > > generate new work, which are not necessarily in the best interest of > the > > protocol. > > In order to reduce these incentives this proposal re-assigns 2 bytes > from > > the version field of the block header to a new extra nonce field. > > # Copyright > > # Specification > > The block version number field in the block header is reduced in > size > from > > 4 to 2 bytes. > > The third and fourth byte in the block header are assigned to the > new > extra > > nonce field inside the block header. > > # Motivation > > The motivation of this proposal is to provide miners with a cheap > > constant-complexity method to create new work that does not require > > altering the transaction tree. > > > > Furthermore, the motivation is to protect the version and timestamp > fields > > in the block header from abuse. > > # Rationale > > Traditionally, the extra nonce is part of the coinbase field of the > > generation transaction, which is always the very first transaction > of > a > > block. > > After incrementing the extra nonce the minimum amount of work a > miner > has > > to do to re-calculate the block header is a) to hash the coinbase > > transaction and b) to re-calculate the left-most branch of the > merkle > tree > > all the way to the merkle root. > > This is necessary overhead a miner has to do besides hashing the > block > > header itself. > > We shall call the process that leads to a new block header from the > same > > transaction set the _pre-hashing_. > > > > First it should be noted that the relative cost of pre-hashing in > its > > traditional form depends > > on the block size, which may create an unwanted incentive for miners > > to keep the block size small. However, this is not the main > motivation for > > the current proposal. > > > > While the block header is hashed by ASICs, pre-hashing typically > happens on > > a CPU because of the greater flexibility required. > > Consequently, as ASIC cost per hash performance drops the relative > cost of > > pre-hashing increases. > > > > This creates an incentive for miners to find cheaper ways to create > new > > work than by means of pre-hashing. > > An example of this currently happening is the on-device rolling of > the > > timestamp into the future. > > These ways of creating new work are unlikely to be in the best > interest of > > the protocol. > > For example, rolling the timestamp faster than the real time is > unwanted > > (more so on faster blockchains). > > > > The version number in the block header is a possible target for > alteration > > with the goal of cheaply creating new work. > > Currently, blocks with arbitrarily large version numbers get relayed > and > > accepted by the network. > > As this is unwanted behaviour, there should not exist any incentive > for a > > miner to abuse the version number in this way. > > > > The solution is to reduce the range of version numbers from 2^32 to > 2 > ^16 > > and to declare the third and forth bytes of the block header as > legitimate > > space for an extra nonce. > > This will reduce the incentive for a miner to abuse the shortened > version > > number by a factor in the order of 2^16. > > > > As a side effect, this proposal greatly reduces the bandwidth > requirements > > of a blind pool protocol by only submitting the block header to the > miner. > > # Backwards Compatibility > > Old versions of the client will accept blocks of this kind but will > throw > > an alert at the user to upgrade. > > The only code change would be a cast of the version number to a > short. > > Besides the upgrade alert, old and new versions of the client can > co-exist > > and there is no need to introduce a new block version number or to > > phase-out old block versions. > > # Reference Implementation > > # Final implementation > > > > > > If changing the structure of the block header, wouldnt you also need to > > increment the version number to 3? > > > ------------------------------------------------------------------------------ > "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE > Instantly run your Selenium tests across 300+ browser/OS combos. Get > unparalleled scalability from the best Selenium testing platform > available. > Simple to use. Nothing to install. Get started now for free." > http://p.sf.net/sfu/SauceLabs > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > > -- Timo Hanke PGP 1EFF 69BC 6FB7 8744 14DB 631D 1BB5 D6E3 AB96 7DA8 ------------------------------------------------------------------------------ Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
