POST-POSEIDON: HASH FUNCTION VARIANTS FOR ETHEREUM

Summary from the TLDR Crypto newsletter

The emergence of Flock as a practical post-quantum proof system for binary circuits removes Ethereum's requirement for circuit-friendly hashes like Poseidon, opening five protocol layers (consensus signatures, CL aggregation, state tree construction, EL signatures, and EL aggregation) to standard hash function candidates. Performance targets set the bar at proving 2^25 bytes per second with LeanVM and approximately 1 million hash calls per second, a throughput floor that filters the field. BLAKE3 leads on raw speed at 7 GB/s parallel and 1.1 cycles per byte on long messages but carries no indifferentiability proofs and a thin cryptanalytic record, and SHA-3 holds 50+ published cryptanalytic papers and sponge-mode indifferentiability proofs but runs at only 0.2 GB/s natively. The research ranks SHA-3 and BLAKE2s as the lowest-risk selections, with SHA-2's length-extension property disqualifying it as a random-oracle substitute despite 45+ cryptanalytic papers.