CTV+CSFS: Can we reach consensus on a first step towards covenants?

[instagibbs]

@instagibbs

I’ve found this use-case the least compelling part, especially at the cost of having to reason about legacy scripting. If it’s really important one idea I’d suggest it be included it as a new segwit output type as a separate feature that lives and dies in a proposal on its own merits. I ended up doing this with P2A for the exact same two reasons.

My technical suggestion for a post-segwit/taproot world:

1. switch to OP_SUCCESSx CTV that pushes to stack (tascript++ only)
2. P2CTV softfork which is defined as a spk of exactly:
   a) <32 bytes data> <OP_NOP5> # for upgrade hook ensuring no one intended to use this otherwise, no corresponding address. Or it could be any other non-segwit template.
   b) OR <2> <32 bytes data> # unknown witness version, has address

Either one would be required to have empty witness data / scriptSig on spend and does otherwise identical hashing checks on spending tx.

Either bare CTV is important or it’s not; it would be pretty trivial to do (2.b) and allows the reviewer to never think about legacy script opcodes at all.