1.5 KiB
9.3: Using CSV in Scripts
NOTE: This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning.
nLockTime and OP_CHECKLOCKTIMEVERIFY (or CLTV) are just one side of the timelock equation. On the other are nSequence and OP_CHECKSEQUENCEVERIFY, which can be used to check against relative times rather than absolute times.
VERSION WARNING: CSV became available with Bitcoin Core 0.12.1, in spring 2016.
Understand nSequence
Every UTXO used in a transaction has an nSequence (or if you prefer sequence) value. It's been a prime tool for Bitcoin expansions. So, if it's not set to 0xffffffff, that's a mark that an unconfirmed transaction is eligible for RBF, as discussed in §5.2: Resending a Transaction with RBF, with increases in the nSequence showing progressively newer replacement transactions. Similarly, a value of less than 0xffffffff tells Bitcoin to pay attention to nLockTime, as described in §6.4 Sending a Transaction with a Locktime.md.
There's one more use nSequence, which was described by BIP 68.
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