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.
NEPTUNE_DEFAULT_GPU=<bus-id>allows you to select the default GPU that tree-builder is going to run on given its bus-id.
(Bus-id is a decimal integer that can be found through nvidia-smi, rocm-smi, lspci and etc.)
The following are likely areas of future work:
- Support for multiple GPUs.
- Support domain separation tag.
- Improve throughput (?) by using OpenCL directly.
Neptune was originally bootstrapped from Dusk's reference implementation.
MIT or Apache 2.0