According to Cointelegraph, a Bitcoin developer has proposed a new method to bring more expressive off-chain smart contracts to Bitcoin (BTC) without requiring a soft fork. In an October 9 white paper titled 'BitVM: Compute Anything on Bitcoin' by ZeroSync's project lead Robin Linus, BitVM enables Turing-complete Bitcoin contracts without altering Bitcoin's consensus rules. A Turing Complete system can theoretically provide an answer to any computational problem.
With BitVM, the 'logic' of Bitcoin contracts would be executed off-chain, but verification would be made on Bitcoin, similar to Ethereum's optimistic rollups. BitVM's architecture is based on fraud proofs and a challenge-response model where a 'prover' can make claims and a 'verifier' can perform a fraud-proof to punish the prover when false claims are made. Linus explained that Bitcoin, in its current form, is limited to basic operations, such as signatures, timelocks, and hashlocks, but that can now be broadened with BitVM, which Linus says can compute a host of interesting applications.
Linus said a limitation of the model is that it is limited to a two-party setting with a prover and a verifier and that a significant amount of off-chain computation and communication is needed to execute programs. Linus said the next 'milestone' is to fully implement the BitVM in addition to Tree++ — a high-level programming language to write and debug Bitcoin contracts. BitVM is enabled by the Taproot soft fork which took place in November 2021.
