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Update 9_2_Using_CLTV_in_Scripts.md

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Shannon Appelcline 2017-05-24 14:30:55 -07:00 committed by GitHub
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9_2_Using_CLTV_in_Scripts.md
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@ -101,6 +101,29 @@ In the case of the above example, the following unlocking script would suffice,
<signature> <pubKey>
```
### Run a CLTV Script
To run the Script, you would first concatenate the unlocking and locking scripts:
```
Script: <signature> <pubKey> <NextYear> OP_CHECKLOCKTIMEVERIFY OP_DROP OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
Stack: [ ]
```
The sthree constants would be pushed onto the stack:
```
Script: OP_CHECKLOCKTIMEVERIFY OP_DROP OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
Stack: [ <signature> <pubKey> <NextYear> ]
```
Then, `OP_CHECKLOCKTIMEVERIFY` would run. It finds something on the stack and verifies that `nSequence` isn't 0xffffffff. Finally, it compares `<NextYear>` with `nLockTime`. If they are both the same sort of representation and if `nLockTime ≥ <NextYear>`, then it successfully processes (else, it ends the script):
```
Script: OP_DROP OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
Stack: [ <signature> <pubKey> <NextYear> ]
```
Then, `OP_DROP` gets rid of that `<NextYear>` left around:
```
Script: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
Stack: [ <signature> <pubKey> ]
```
Finally, the remainder of the script runs, which is a normal check of a signature and public key.
## Summary: Using CLTV in Scripts
`OP-CHECKLOCKTIMEVERIFY` is a simple opcode that looks at a single arguments, interprets it as a blockheight or UNIX timestamp, and only continues with a UTXO's redemption if that blockheight or UNIX timestamp is in the past. Setting `nLockTime` on the new transaction is what allows Bitcoin to make this calculation.