Based on your description, it seems like you want to create a script that enforces a 2-of-3 multisig with a timelock. A and B can spend the UTXO together before the timelock, but after the timelock expires, C can spend the UTXO with either A or B.
The script you provided is almost correct, but there's a small mistake. Here's the corrected version:
OP_IF
2
OP_ELSE
OP_CHECKSEQUENCEVERIFY OP_DROP
OP_CHECKSIGVERIFY
OP_ENDIF
2 OP_CHECKMULTISIG
In the script above, replace
with the desired timelock value (in blocks or seconds) and , , and with the respective public keys or their corresponding script hashes.
The modified script enforces the following conditions:
If the condition inside OP_IF is true (timelock has not expired):
The top stack element should be the number 2 (indicating a 2-of-2 multisig condition between A and B).
If the condition inside OP_ELSE is true (timelock has expired):
The top stack element should be the timelock value.
C's public key or script hash should successfully verify using OP_CHECKSIGVERIFY.
Finally, , , and the number 2 are used for the final 2-of-2 multisig check.
Remember to provide the actual values for , , , and when implementing this script in a real-world scenario .
Hi, thank you for suggestion. But I don't understand how the OP_ELSE branch makes key_C and key_A enough to unlock the script? Because from your explanation, key_C should verify, then both key_A and key_B should do the 2-of-2 multisig check.
And I also don't get how is this 2-of-2 multisig produced, since the OP_ELSE branch doesn't provide a threshold number for the OP_CHECKMULTISIG. That's why I provide the number 1 before ENDIF to make 1 key_A key_B 2 CHECKMULTISIG.
BTW, I have changed the script to miniscript, any suggestions to this?
wsh(thresh(2,pk(A),s:pk(B),sj:and_v(v:pk(C),n:older(1728))))
A OP_CHECKSIG OP_SWAP
B OP_CHECKSIG OP_ADD OP_SWAP OP_SIZE OP_0NOTEQUAL
OP_IF
C OP_CHECKSIGVERIFY 1728 OP_CHECKSEQUENCEVERIFY OP_0NOTEQUAL
OP_ENDIF
OP_ADD 2 OP_EQUAL
