bitcoin/bitcoin

That OP_NOP10 is the last executable opcode is a bit of a obscure trivia, and the MAX_OPCODE constant already exists. This merely standardizes use of MAX_OPCODE over OP_NOP10 where it makes sense and is more clear.

- Replace NOP3 with CHECKSEQUENCEVERIFY (BIP112)
  <nSequence> CHECKSEQUENCEVERIFY -> <nSequence>
- Fails if txin.nSequence < nSequence, allowing funds of a txout to be locked for a number of blocks or a duration of time after its inclusion in a block.
- Pull most of CheckLockTime() out into VerifyLockTime(), a local function that will be reused for CheckSequence()
- Add bitwise AND operator to CScriptNum
- Enable CHECKSEQUENCEVERIFY as a standard script verify flag
- Transactions that fail CSV verification will be rejected from the mempool, making it easy to test the feature. However blocks containing "invalid" CSV-using transactions will still be accepted; this is *not* the soft-fork required to actually enable CSV for production use.

…me constraints

Transactions are not allowed in the memory pool or selected for inclusion in a block until their lock times exceed chainActive.Tip()->GetMedianTimePast(). However blocks including transactions which are only mature under the old rules are still accepted; this is *not* the soft-fork required to actually rely on the new constraint in production.

…t for lock-time calculations

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.

… "two times of nLockTime." What is meant is that there are two kinds, or categories of nLockTime.

If/when CTransaction::CURRENT_VERSION is incremented, this will break CChainParams and the miner tests. This fix sets the transaction version explicitly where we depend on the hash value (genesis block, proof of work checks).

Under some circumstances it is possible for there to be a significant,
discontinuous jump in a node's clock value. On mining nodes, this can
result in block templates which are no longer valid due to time-based
nLockTime constraints. UpdateTime() is modified so that it will never
decrease a block's nLockTime, thereby preventing such invalidations.

This indentation should have been stripped out when AreInputsStandard was made a top-level function instead of a CTransaction method.