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nadams 2017-04-24 13:28:24 -07:00
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@ -229,7 +229,7 @@ Timelocks are useful for post-dating transactions and locking funds to a date in
[[transaction_locktime_nlocktime]]
==== Transaction Locktime (nLocktime)
From the beginning, bitcoin has had a transaction-level timelock feature. ((("locktime")))((("transactions","nLockTime")))Transaction locktime is a transaction-level setting (a field in the transaction data structure) that defines the earliest time that a transaction is valid and can be relayed on the network or added to the blockchain. Locktime is also known as +nLocktime+ from the variable name used in the Bitcoin Core codebase. It is set to zero in most transactions to indicate immediate propagation and execution. If +nLocktime+ is nonzero and below 500 million, it is interpreted as a block height, meaning the transaction is not valid and is not relayed or included in the blockchain prior to the specified block height. If it is above 500 million, it is interpreted as a Unix Epoch timestamp (seconds since Jan-1-1970) and the transaction is not valid prior to the specified time. Transactions with +nLocktime+ specifying a future block or time must be held by the originating system and transmitted to the bitcoin network only after they become valid. If a transaction is transmitted to the network before the specified +nLocktime+, the transaction will be rejected by the first node as invalid and will not be relayed to other nodes. The use of nLockTime is equivalent to postdating a paper check.
From the beginning, bitcoin has had a transaction-level timelock feature. ((("locktime")))((("transactions","nLockTime")))Transaction locktime is a transaction-level setting (a field in the transaction data structure) that defines the earliest time that a transaction is valid and can be relayed on the network or added to the blockchain. Locktime is also known as +nLocktime+ from the variable name used in the Bitcoin Core codebase. It is set to zero in most transactions to indicate immediate propagation and execution. If +nLocktime+ is nonzero and below 500 million, it is interpreted as a block height, meaning the transaction is not valid and is not relayed or included in the blockchain prior to the specified block height. If it is above 500 million, it is interpreted as a Unix Epoch timestamp (seconds since Jan-1-1970) and the transaction is not valid prior to the specified time. Transactions with +nLocktime+ specifying a future block or time must be held by the originating system and transmitted to the bitcoin network only after they become valid. If a transaction is transmitted to the network before the specified +nLocktime+, the transaction will be rejected by the first node as invalid and will not be relayed to other nodes. The use of +nLocktime+ is equivalent to postdating a paper check.
[[locktime_limitations]]
===== Transaction locktime limitations
@ -277,7 +277,7 @@ To lock it to a time, say 3 months from now, the transaction would be a P2SH tra
where +<now {plus} 3 months>+ is a block height or time value estimated 3 months from the time the transaction is mined: current block height {plus} 12,960 (blocks) or current Unix epoch time {plus} 7,760,000 (seconds). For now, don't worry about the +DROP+ opcode that follows +CHECKLOCKTIMEVERIFY+; it will be explained shortly.
When Bob tries to spend this UTXO, he constructs a transaction which references the UTXO as an input. He uses his signature and public key in the unlocking script of that input and sets the transaction nLocktime to be equal or greater to the timelock in the +CHECKLOCKTIMEVERIFY+ Alice set. Bob then broadcasts the transaction on the bitcoin network.
When Bob tries to spend this UTXO, he constructs a transaction that references the UTXO as an input. He uses his signature and public key in the unlocking script of that input and sets the transaction nLocktime to be equal or greater to the timelock in the +CHECKLOCKTIMEVERIFY+ Alice set. Bob then broadcasts the transaction on the bitcoin network.
Bob's transaction is evaluated as follows. If the +CHECKLOCKTIMEVERIFY+ parameter Alice set is less than or equal the spending transaction's +nLocktime+, script execution continues (acts as if a NOP opcode was executed). Otherwise, script execution halts and the transaction is deemed invalid.