Examining ScriptPubkeys in Bitcoin Script

In an email, the sender shares their exploration of the requirements to validate Taproot outputs in Bitcoin Script. They mention that such functionality is necessary for usable vaults. The sender provides a link to a blog post where they discuss this exploration in detail (https://rusty.ozlabs.org/2023/10/20/examining-scriptpubkey-in-script.html). They also invite others to collaborate on producing a prototype and debugging their script examples.

The sender summarizes their findings as follows: If OP_TX/OP_TXHASH or an equivalent way of pushing a scriptPubkey on the stack is available, and additional opcodes like OP_MULTISHA256 (or OP_CAT), OP_KEYADDTWEAK, OP_LESS (or OP_CONDSWAP) are added, along with a soft-fork to weaken the OP_SUCCESSx rule (or pop-script-from-stack), it becomes possible to prove a two-leaf tapscript tree in approximately 110 bytes of Script. This enables the implementation of useful spending constraints based on a template approach.

The email concludes with a thank you from Rusty, the sender.