BIP 443: OP_CHECKCONTRACTVERIFY

Hi all,

This is a draft for the formal specifications of the OP_CHECKCONTRACTVERIFY (CCV) opcode.

CCV enables to build Script-based state machines that span across multiple transactions, by providing an ergonomic tool to commit to - and introspect - the Script and possibly some data that is committed inside inputs or outputs.

Related to this PR:

• Implementation in bitcoin-core
• Post on delving bitcoin, focusing on the amount logic of the opcode.

Not covered in this draft:

• sigops budget (benchmarks needed)
• activation logic
• policy considerations (if any)

I recommend delving bitcoin for high level discussions about alternative implementations, applications, etc.