Oleksandr Kurbatov, Yaroslav Panasenko, Volodymyr Dubinin, and Yevhen Hrubiian, Distributed Lab, Ukraine

We present Free-Delete, a censorship-resistant group-chat protocol whose membership is validated by non-fungible-token (NFT) ownership while user privacy ranges across five selectable modes. A single Groth16 circuit, anchored in a sparse Merkle tree of verifiable commitments, realises (i) Fully Anonymous messaging, (ii) Linkable Anonymous reputation building, (iii) Publicly Identified disclosure, (iv) Confidential end-to-end encryption, and (v) Rate-Limited Accountability that revokes keys on spam—all without moderator involvement or economic deposits. A black-paper prototype written in TypeScript, Circom 2, and Solidity achieves 0.35 s for register and 1.38 s for postMessage on consumer hardware; on-chain verification costs 3–5.5×105 gas per proof on Polygon. These results demonstrate that NFT-gated, stake-free, privacy-preserving communication can be deployed today on any EVM chain.

NFT authentication, zero-knowledge proofs, decentralised chat, sparse Merkle tree, ratelimiting nullifiers, forward secrecy