what's EVM PORST?

EVM PORST is a Solidity implementation of the PORST signature scheme from Gravity-SPHINCS, serving as an advanced post-quantum (PQ) cryptographic building block optimized for the Ethereum Virtual Machine (EVM). It surpasses existing PQ schemes like HORS(T) and FORS (from SPHINCS+) by minimizing witness sizes, reducing verifier workloads, and lowering gas costs for on-chain signature verification and relay. PORST employs few-time signatures paired with XMSS for state synchronization, aligning well with the EVM's sporadic state update patterns, unlike stateless alternatives. The implementation, crafted primarily in Yul assembly via Foundry with zero dependencies, streamlines signature data by hashing only essential witness words for public key root derivation and computes efficient Merkle octopus paths on-chain. EVM memory limitations prompted simpler data structures over complex ones like binary heaps. Developed solo over ~12 hours at ETHGlobal Cannes 2026, it demonstrates viability for PQ-secure wallets and applications on Ethereum.

EVM PORST named a top 10 finalist at ETHGlobal Cannes hackathon on 2026-04-05.