Ethereum's Future: WASM vs. RISC-V Debate Ignites Infrastructure Discussion

A significant debate is unfolding within the Ethereum community regarding the future of its execution layer. Offchain Labs, the developer behind Arbitrum, has publicly challenged Vitalik Buterin's proposal to adopt RISC-V as Ethereum's primary instruction set architecture (ISA). The core of the disagreement lies in whether RISC-V is the optimal choice for smart contract delivery on Ethereum's Layer 1 (L1).

Key Takeaways

• Offchain Labs researchers argue that WebAssembly (WASM) is a superior long-term solution for Ethereum's L1 smart contract format compared to RISC-V.

• They propose separating the "delivery ISA" (dISA) for smart contracts from the "proving ISA" (pISA) used for Zero-Knowledge (ZK) proofs.

• WASM offers advantages in terms of structured design, ease of modification, efficient hardware execution, and a mature tooling ecosystem.

The RISC-V Proposal and Offchain Labs' Counterargument

Ethereum co-founder Vitalik Buterin had previously suggested replacing the Ethereum Virtual Machine's bytecode with RISC-V, an open-source ISA. The primary motivation was the potential to drastically reduce on-chain ZK proving costs, possibly by up to 100x. However, four researchers from Offchain Labs have voiced concerns, arguing that while RISC-V might be beneficial for ZK proofs, it's not necessarily the best fit for how smart contracts should be delivered and stored on the blockchain.

Separating Delivery and Proving ISAs

The central thesis from Offchain Labs is the distinction between a "delivery ISA" (dISA) and a "proving ISA" (pISA). They contend that these two functions do not need to be served by the same architecture. To demonstrate this, Offchain Labs is developing a prototype where Arbitrum blocks, utilizing WASM-based Stylus smart contracts, are ZK-proven by first compiling WASM to RISC-V and then proving the RISC-V execution. This approach suggests that a blockchain can use WASM as its dISA while employing a RISC-V-based ZK-Virtual Machine (VM) as a backend for proving.

Concerns About RISC-V's Long-Term Viability

The Offchain Labs team also expressed skepticism about RISC-V representing the final word in ZK-VM evolution, given the rapid pace of change in the proving landscape. They warn that enshrining RISC-V on Ethereum's L1 could lock the network into a specific proving technology, potentially hindering the adoption of superior alternatives as they emerge. They point to WASM-based ZK-VMs, such as Ligero's Ligetron, as examples of promising developments that might offer advantages hardware-focused ISAs cannot match. Furthermore, they note that ZK proving costs have already significantly decreased, making the optimization solely for proving efficiency less critical.

WASM's Strengths for Ethereum

Offchain Labs highlighted several advantages of WASM. Its structured design facilitates easier code modification and optimization without jeopardizing existing contracts. WASM also executes efficiently on common hardware, unlike RISC-V, which would likely require emulation on most Ethereum nodes. The researchers emphasized WASM's robust validation capabilities, ensuring type safety and preventing vulnerabilities, alongside its mature and battle-tested tooling ecosystem.

They concluded by likening WASM to an "Internet Protocol for smart contracts," serving as an ideal intermediate layer between diverse source languages and the various backends used for execution and proving.

Sources

• Offchain Labs challenges Vitalik's RISC-V proposal, says WASM better for Ethereum L1, The Block.