A New Proposal for Off-Chain Smart Contracts on Bitcoin
A Bitcoin developer named Robin Linus has introduced a new method to implement expressive off-chain smart contracts on the Bitcoin network. This proposal, called BitVM, allows for Turing-complete Bitcoin contracts without requiring a soft fork. Similar to Ethereum’s optimistic rollups, BitVM executes the logic of the contracts off-chain while verifying them on the Bitcoin blockchain.
BitVM operates using fraud proofs and a challenge-response model. It enables a “prover” to make claims and a “verifier” to perform fraud-proof checks, penalizing the prover for false claims. While Bitcoin currently supports basic operations like signatures and timelocks, BitVM expands its capabilities to include applications such as games, verification of validity proofs in Bitcoin contracts, bridging BTC to foreign chains, prediction markets, and emulating novel opcodes.
Reactions from the Bitcoin Community
Members of the Bitcoin community have responded positively to the BitVM proposal. Eric Wall, a prominent Bitcoiner, expressed cautious excitement about the real-world experiments that may arise from this development. Dylan LeClair, a Bitcoin analyst, was impressed with BitVM’s white paper. However, Adam Back, a Bitcoin Core contributor, advised not to get overly excited yet since it is essentially a generalization of a two-party game.
There is already a proof-of-concept available on GitHub for those interested in exploring BitVM further. It’s important to note that BitVM is an opt-in system that doesn’t force users to lock their coins into Turing complete smart contracts if they don’t want to. Some members of the community believe that BitVM will contribute to pushing Bitcoin’s price forward in the next bull market.
Hot Take: BitVM Expands Possibilities for Bitcoin Contracts
BitVM presents an innovative approach to enable more expressive off-chain smart contracts on the Bitcoin network. By introducing fraud proofs and a challenge-response model, BitVM allows for Turing-complete computations without altering Bitcoin’s consensus rules. This proposal opens up a range of new applications, including games, verification of validity proofs, bridging BTC to foreign chains, prediction markets, and more. While there are limitations and concerns within the Bitcoin community regarding this development, BitVM has generated excitement and curiosity about its potential impact on the future of Bitcoin contracts.
A Bitcoin developer has proposed a new way to bring more expressive off-chain smart contracts to Bitcoin (BTC) without needing a soft fork.
Announced in an Oct.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.
“Any computable function can be verified on Bitcoin” pic.twitter.com/CLQv49Ydsg
— яobin linus (@robin_linus) October 9, 2023
A Turing Complete system is one which 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.
“Potential applications include games like Chess, Go, or Poker, and particularly, verification of validity proofs in Bitcoin contracts.”
“Additionally, it might be possible to bridge BTC to foreign chains, build a prediction market, or emulate novel opcodes,” said Linus.
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.
Linus cited Ethereum research into optimistic rollups and a study on Merkle Trees in contributing to the eight-page white paper.
Bitcoiners respond to BitVM
Prominent Bitcoiner Eric Wall posted on X (Twitter) that the concepts outlined in the BitVM white paper “check out” and is “cautiously excited” to see what real-world experiments stem from it.
Bitcoin analyst Dylan LeClair is also impressed with BitVM’s white paper. But Adam Back, a Bitcoin Core contributor suggested that people shouldn’t get too excited about the development just yet.
for people getting (over) excited, this is cool but effectively a generalization of a two-party game – it says right in the abstract – so it’s a bit like Greg Maxwell’s 2016 ZKP contingent payments implemented example https://t.co/OeHRsbFjud
— Adam Back (@adam3us) October 9, 2023
One builder in the blockchain space, “dotta,” noted that there is already a proof-of-concept on GitHub.
Another X user, Sam Parker, attempted to resolve a common fear among Bitcoin maximalists by explaining that BitVM won’t force Bitcoin’s to be “locked” into these contracts.
“Finally, this is opt-in. If you don’t trust your coins being locked to some Turing complete contract (totally reasonable) then don’t lock them to a Turing complete smart contract. One of [the] beauties of the UTXO system is security sandboxing.”
Others, such as “psage” say BitVM adds to the list of things that will push Bitcoin’s price forward in the next bull market.
The bullish stuff around #Bitcoin is snowballing, lots of them controversial, nevertheless a few off my finger tips:
– BitVM
– Ordinals
– Multiple Pres Candidates talking about it
– ETF
– Halving
– Privacy improvements
– Exponential Hash Rate increase
– Countries mining
….— psage (@perspiringsage) October 9, 2023
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