Following up on my earlier CAT/CSFS/CTV runs, I tested an IK + CSFS composition on Bitcoin Inquisition.
This uses OP_INTERNALKEY to source the pubkey from Taproot execution context rather than witness.
Commit: 9930e922…0ea8
Reveal: 8d0b2156…dd8f
Script: OP_INTERNALKEY OP_CHECKSIGFROMSTACK (cbcc)
Witness: [sig, message] — no pubkey in witness
Observation:
- Pubkey is no longer caller-supplied
- It is sourced from Taproot execution context (internal key)
This shifts authorization from “who provides a key” to “who created the UTXO”.
However, since the message is fixed, the (sig, message) pair is replayable across UTXOs with the same internal key.
Full breakdown (stack / control block / derivation): details: https://medium.com/@aaron.recompile/op-internalkey-op-checksigfromstack-on-signet-identity-bound-authorization-04f0440557bc