Neptune

About

Neptune is a Rust implementation of the Poseidon hash function tuned for Filecoin.

Neptune has been audited by ADBK Consulting and deemed fully compliant with the paper (Starkad and Poseidon: New Hash Functions for Zero Knowledge Proof Systems).

Neptune is specialized to the BLS12-381 curve. Although the API allows for type specialization to other fields, the round numbers, constants, and s-box selection may not be correct. Do not do this.

Hashes of arbitrary arities are generally supported — but secure round numbers have only been calculated for a selection (including especially 2, 4, and 8 — which are explicitly, rather than incidentally, supported). Filecoin Proofs make heavy use of 8-ary merkle trees and merkle inclusion proofs (in SNARKs).

Neptune also supports batch hashing and tree building, which can be performed on a GPU. The underlying GPU implementation, neptune-triton is implemented in the Futhark Programming Language.

At the time of the 1.0.0 release, Neptune on RTX 2080Ti GPU can build 8-ary Merkle trees for 4GiB of input in 16 seconds.

Future Work

The following are likely areas of future work:

• Support for multiple GPUs.
• Support domain separation tag.
• Improve throughput (?) by using OpenCL directly.

History

Neptune was originally bootstrapped from Dusk's reference implementation.

License

MIT or Apache 2.0