I ran a small experiment on Bitcoin Inquisition Signet using: OP_INTERNALKEY OP_CHECKSIGFROMSTACK.
Confirmed spend:
https://mempool.space/signet/tx/8d0b2156e9425afe64cabf3c906da255b6b86c51cb8968f828d5253fc261dd8f
In plain CSFS, the witness provides (sig, msg, pubkey), so the script checks whether someone signed the message.
With OP_INTERNALKEY, the pubkey comes from Taproot context instead of witness.
A possible framing:
- CSFS: “did someone sign this message?”
- IK + CSFS: “did the Taproot internal key holder sign this message?”
This seems to turn CSFS into a kind of identity-bound authorization primitive.
Is this a useful way to think about it?
Where does this interpretation break?
