AirbenderMatter Labs

Description

Airbender is the most advanced zkVM developed by Matter Labs. It operates on RISC-V ISA and is designed to prove state transition function of zk stack chains in combination with ZKsync OS, but also more general RISC-V programs. Airbender proofs could be wrapped into Fflonk SNARK for efficient onchain verification. Airbender initial release targets 81 bits of security.

Proof system

Airbender implements a rather standard zkVM: AIR constraints, DEEP-FRI polynomial testing, RISC-V instructions with the program being stored in read-only memory and accessed by lookup arguments, recursive proving. Many parts of the stack are optimized for speed and efficiency, including a small Mersenne31 field over which the computation trace is generated and a simple degree 2 AIR constraints. Airbender prover could also be run in application mode without signed multiplication and division operations, thus reducing circuit complexity.

Recursion circuits

Airbender targets proving batches of size 2**22 (~4 M) clock cycles. The proofs of such batches are pairwise recursively aggregated using zkVM in recursion mode. For onchain verification, the final Airbender STARK is compressed using Boojum compressor and then wrapped into a Fflonk SNARK with KZG. The KZG commitment is done over BN254 curve and it uses Aztec Ignition trusted setup ceremony, see below for more details.