BIP draft: Merkelized Abstract Syntax Tree

BIP draft: https://github.com/jl2012/bips/blob/mast/bip-mast.mediawiki Reference implementation: https://github.com/jl2012/bitcoin/commit/f335cab76eb95d4f7754a718df201216a49 75d8c

This BIP defines a new witness program type that uses a Merkle tree to encode mutually exclusive branches in a script. This enables complicated redemption conditions that are currently not possible, improves privacy by hiding unexecuted scripts, and allows inclusion of non-consensus enforced data with very low or no additional cost.

The reference implementation is a small and simple patch on top of BIP141 (segwit), however, I have no intention to push this before segwit is enforced. Instead, I hope the MAST will come with many new op codes, particularly Schnorr signature.