BitVMX: a CPU for Universal Computation on Bitcoin

[tromp]

https://bitvmx.org/

> Secure, Extensible, Open-Source
BitVMX is a new framework to optimistically execute arbitrary programs in Bitcoin based on the N-party disputable computation paradigm pioneered by BitVM. BitVMX framework provides the foundations to run any CPU on Bitcoin, with a focus to run a fully-compliant RISC-V processor programmable using a standard compilation toolchain.

> Our vision is to create a secure, extensible, open-source, peer-reviewed and sidechain-agnostic framework that can be used to develop blockchain bridges, aggregator oracles, and SNARK/STARK verifiers. As soon as BitVMX is able to run a SNARK verifier, a myriad of new use cases can be brought to Bitcoin, from ZK-rollups to crazy use cases such as Zero Knowledge Contingent Payments (i.e. autonomous bug bounties paid for disclosure of vulnerabilities).

> How Does BitVMX Work ...

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[NotATether]

Fantastic!

So this basically makes Bitcoin scripts Turing-complete?

[ABCbits]

RISC-V support? I must say it's rather specific goal. While the technical details go over my head, it's good there's major improvement on preprocessing time and storage space. I recall simple operation using BitVM use over 20KB of data.

Fantastic!

So this basically makes Bitcoin scripts Turing-complete?

As reminder, BitVM (the predecessor) already allows turing-complete script. See https://bitvm.org/bitvm.pdf.

[Sergio_Demian_Lerner]

The key differences between BitVM1 and BitVMX are the amount of pre-computation required, the transaction space consumed, and more importantly, the complexity of the solution.

Regarding pre-computation, BitVM1 requires computing large Merkle trees (2^32 elements in size). BitVMX does not require to compute any Merkle tree.

Regarding onchain footprint, in the optimistic case, both BitVM1 and BitVMX require just one multi-signed transaction. But in the pessimistic case, if one of the parties is malicious, then BitVM1 may require more than 250K of virtual bytes (in total between both parties). This is my estimation, not a precise number, because BitVM1 was never finished. In contrast, BitVMX consumes less than 160K of virtual bytes.

Also BitVMX can be parametrized to require half the number of interaction rounds compared to BitVM1, at the expense of higher space consumed. 

Finally, BitVMX is much simpler. I think anyone will understand it in 10 minutes.

While the bitvmx.org site has some information, the first paper will be published just before BTC++ (May 1, '24).

[Sergio_Demian_Lerner]

FYI the BitVMX paper is available at https://bitvmx.org

There is a Telegram channel for devs and a twitter account for updates.

[NotATether]

FYI the BitVMX paper is available at https://bitvmx.org

There is a Telegram channel for devs and a twitter account for updates.

That's great.

Clearly we need to start writing software to support this.