This disentangles the script validation skipping from checkpoints.
A new option is introduced "assumevalid" which specifies a block whos
ancestors we assume all have valid scriptsigs and so we do not check
them when they are also burried under the best header by two weeks
worth of work.
Unlike checkpoints this has no influence on consensus unless you set
it to a block with an invalid history. Because of this it can be
easily be updated without risk of influencing the network consensus.
This results in a massive IBD speedup.
This approach was independently recommended by Peter Todd and Luke-Jr
since POW based signature skipping (see PR#9180) does not have the
verifiable properties of a specific hash and may create bad incentives.
The downside is that, like checkpoints, the defaults bitrot and older
releases will sync slower. On the plus side users can provide their
own value here, and if they set it to something crazy all that will
happen is more time will be spend validating signatures.
Checkblocks and checklevel are also moved to the hidden debug options:
Especially now that checkblocks has a low default there is little need
to change these settings, and users frequently misunderstand them as
influencing security or IBD speed. By hiding them we offset the
space added by this new option.
This introduces a 'minimum chain work' chainparam which is intended
to be the known amount of work in the chain for the network at the
time of software release. If you don't have this much work, you're
not yet caught up.
This is used instead of the count of blocks test from checkpoints.
This criteria is trivial to keep updated as there is no element of
subjectivity, trust, or position dependence to it. It is also a more
reliable metric of sync status than a block count.
- BIP9DeploymentInfo struct for static deployment info
- VersionBitsDeploymentInfo: Avoid C++11ism by commenting parameter names
- getblocktemplate: Make sure to set deployments in the version if it is LOCKED_IN
- In this commit, all rules are considered required for clients to support
SequenceLocks functions are used to evaluate sequence lock times or heights per BIP 68.
The majority of this code is copied from maaku in #6312
Further credit: btcdrak, sipa, NicolasDorier
This switches the Merkle tree logic for blocks to one that runs in constant (small) space.
The old code is moved to tests, and a new test is added that for various combinations of
block sizes, transaction positions to compute a branch for, and mutations:
* Verifies that the old code and new code agree for the Merkle root.
* Verifies that the old code and new code agree for the Merkle branch.
* Verifies that the computed Merkle branch is valid.
* Verifies that mutations don't change the Merkle root.
* Verifies that mutations are correctly detected.
Revert "Revert "Add rules--presently disabled--for using GetMedianTimePast as endpoint for lock-time calculations""
This reverts commit 40cd32e835.
After careful analysis it was determined that the change was, in fact, safe and several people were suffering
momentary confusion about locktime semantics.
This reverts commit 9d55050773.
As noted by Luke-Jr, under some conditions this will accept transactions which are invalid by the network
rules. This happens when the current block time is head of the median time past and a transaction's
locktime is in the middle.
This could be addressed by changing the rule to MAX(this_block_time, MTP+offset) but this solution and
the particular offset used deserve some consideration.
The lock-time code currently uses CBlock::nTime as the cutoff point for time based locked transactions. This has the unfortunate outcome of creating a perverse incentive for miners to lie about the time of a block in order to collect more fees by including transactions that by wall clock determination have not yet matured. By using CBlockIndex::GetMedianTimePast from the prior block instead, the self-interested miner no longer gains from generating blocks with fraudulent timestamps. Users can compensate for this change by simply adding an hour (3600 seconds) to their time-based lock times.
If enforced, this would be a soft-fork change. This commit only adds the functionality on an unexecuted code path, without changing the behaviour of Bitcoin Core.
Add a field `strDebugMessage` which can be passed to DoS or Invalid,
and queried using GetDebugMessage() to add extra troubleshooting
information to the validation state.
Jorge Timón