Hisoka IO
April 2026
Every blockchain interaction leaks network-layer metadata. Zero-knowledge proofs hide transaction content but leave IP addresses, submission timing, and relay payment traces exposed. Mix networks defend against traffic analysis but provide no mechanism for anonymous on-chain interaction. Composing the two as independent layers reintroduces correlation at the boundary: packet timing at the mix network exit correlates with transaction appearance in the mempool, and the relay payment creates an on-chain fingerprint.
Nox is a Sphinx mixnet co-designed with an anonymous transaction relay layer for Ethereum. Exit nodes submit transactions on behalf of anonymous senders. A zero-knowledge gas payment circuit proves relay fee sufficiency without revealing the payer. An execution-hash commitment inside the proof binds each payment to a specific on-chain action. The reply returns through a Single-Use Reply Block (SURB).
Nox applies Reed-Solomon forward error correction to SURB response channels. With 11 data shards and 4 parity shards, multi-fragment delivery rises from 31% to 98% at 10% packet loss without retransmission. FEC has not previously been applied to anonymous reply channels in any mix network. A full open-source implementation is available and deployed on Arbitrum Sepolia.
Reed-Solomon forward error correction applied to SURB response channels. With d=11 data shards and p=4 parity shards, delivery at 10% packet loss rises from 31.0% to 98.2% at a fixed 26.7% bandwidth overhead. First application of FEC to anonymous reply channels in any mix network.
Full-pipeline evaluation covering per-hop Sphinx processing (58.6 μs mean, 2.5× faster than Katzenpost's equivalent NIKE configuration), end-to-end latency (100.1 ms median under Poisson mixing), sustained throughput (372.3 packets per second), network scaling (5 to 50 nodes), FEC recovery curves, and Shannon entropy analysis.
A zero-knowledge gas payment circuit proves relay fee sufficiency without revealing the payer. An execution hash inside the proof binds each payment to a specific on-chain action, preventing proof reuse and front-running.
@misc{madaram2026nox,
title = {Nox: A Sphinx Mixnet for Anonymous Blockchain Transaction Relay},
author = {Madaram, Jayendra and Sakiv, Reze},
year = {2026},
howpublished = {\url{https://papers.hisoka.io/nox}},
note = {Hisoka IO},
}