Subject: Re: [bitcoin-dev] CTV BIP Meeting #9 Notes

From: ZmnSCPxj <[email-masked]>
Date: Fri, 20 May 2022 23:47:54 +0000

Good morning fd0,

> > In addition, covenant mechanisms that require large witness data are probably more vulnerable to MEV.
>
>
> Which covenant mechanisms require large witness data?

`OP_CSFS` + `OP_CAT`, which requires that you copy parts of the transaction into the witness data if you want to use it for covenants.
And the script itself is in the witness data, and AFAIK `OP_CSFS` needs large scripts if used for covenants.

Arguably though `OP_CSFS` is not designed for covenants, it just *happens to enable* covenants when you throw enough data at it.

If we are going to tolerate recursive covenants, we might want an opcode that explicitly supports recursion, instead of one that happens to enable recursive covenants, because the latter is likely to require more data to be pushed on the witness stack.
E.g. instead of the user having to quine the script (i.e. the script is really written twice, so it ends up doubling the witness size of the SCRIPT part), make an explicitly quining opcode.

Basically, Do not Repeat Yourself.

Regards,
ZmnSCPxj