MATT (Merkleize All The Things)

MATT is an approach for bitcoin smart contracts that is designed to be extremely simple, yet powerful.
It could be enabled as a soft fork with various combinations of opcodes. The most direct way is based on an opcode called OP_CHECKCONTRACTVERIFY (CCV).

Key applications include:

• Scaling and privacy with more powerful layer 2 constructions.
• Trustless bridges for optimistic rollups or other sidechains.
• Vaults for better self custody.

By enabling scalable fraud proof protocols for arbitrary computations, it would bring permissionless innovation in the bitcoin's layer 2 space, while keeping Bitcoin's layer 1 simple and minimalistic.

Start here
    Gentle introduction on StackExchange: A beginner-friendly explanation of MATT and its core concepts.
    FAQ Answers to common questions about MATT, its implementation, and use cases.

Specs and implementation
    BIP-443
    bitcoin-core implementation
    Discussion on the amount logic of OP_CHECKCONTRACTVERIFY

Presentations
▶️ Merkleize All The Things. Advancing Bitcoin Conference − London, March 2nd, 2023. Slides
An introduction to MATT and how it enables scalable fraud proofs on Bitcoin.

▶️ sMATT Contracts Zero to Hero. btc++ − Austin, May 3rd, 2024. Slides
A deep dive into MATT and the pymatt Python framework, with a re-implementation of James O’Beirne's vaults using CCV.
Timestamps:
    Intro to MATT
    Vaults
    Vault demo
    Code in pymatt

Programming with MATT

• Docker image of bitcoin-inquisition + OP_CHECKCONTRACTVERIFY + OP_CAT + OP_CTV for regtest.
• pymatt Python framework for MATT smart contracts, and examples.

Research

• Games in the head (and fraud proofs for the plebs): an exploration on how to optimize 2-party fraud proof protocols implemented with MATT, and an estimate of the worst-case on-chain costs.
• Aggregate delegated exit for L2 pools: an approach for a fraud-proof based exit protocol for shared UTXOs that would allow many users to cooperate in order to withdraw their money.
• elftrace: Johan Torås Halseth's prototype of a compiler for arbitrary computation to RISC-V, and verify in Bitcoin Script via MATT's fraud proofs.
  • ▶️ Optimistic execution of RISC-V in Tapscript: Presentation at btc++ − Austin, May 1st, 2024.

bitcoin-dev

• Original bitcoin-dev post
  • Example of fraud proof protocol instance
• Vaults in the MATT framework and code example
• MATT plays Rock-Paper-Scissors + errata
• Johan Torås Halseth's demonstration of CoinPools exit clause using MATT and Merkle trees. (docs) + (code)