Module signing 

Lighter L2 transaction signing.

Lighter signs transactions with Schnorr signatures over the ecgfp5 curve (Pornin, 2022), defined over the quintic extension field of the Goldilocks prime p = 2^64 - 2^32 + 1, with Poseidon2 as the binding hash.

This module is an original in-tree Rust implementation written from public specifications and permissively licensed references. For the field and curve, Thomas Pornin’s MIT-licensed Rust code at pornin/ecgfp5 serves as a reading reference alongside the curve’s design paper. For Poseidon2 and the Schnorr binding Lighter applies, the Go library elliottech/poseidon_crypto is the behavioural reference: parameter sets (round constants, MDS matrices) are pulled from there as facts, and test vectors derived from it are reproduced as fixtures so equivalence with the upstream behaviour is verifiable end-to-end.

Pornin’s reference stays in the publish=false fuzz crate so the crates.io package graph does not depend on a git source. The fuzz_pornin_diff_* targets assert public algebra operations (Fp5 add/sub/mul/neg/invert, Scalar add/sub/mul/neg, Point decode/double/add, scalar mul on arbitrary bases) byte-for-byte against the reference. The two implementations share no code lineage: Pornin’s accompanies the design paper (IACR ePrint 2022/274) and has been public and reused by downstream zero-knowledge projects since 2022; ours is written from the paper using his code as a reading reference. A bug that slips the differential gate would have to be present in both implementations in the same way, which is concretely unlikely rather than merely theoretically possible.

The official lighter-go and lighter-python SDKs wrap a closed-source compiled signer; round-trip testing against testnet provides the final correctness gate for what the Lighter sequencer accepts.

See crates/adapters/lighter/licenses/THIRD_PARTY_LICENSES.md for the attribution covering reference parameters and test vectors.

Modules

auth_token

Lighter REST/WebSocket auth-token builder.

curve

ECgFp5 elliptic curve and its scalar field, as used by the Lighter signer.

field

Field arithmetic underpinning Lighter’s L2 signing scheme.

hash

Poseidon2 hash over the Goldilocks field used by the Lighter signer.

nonce

Per-(account_index, api_key_index) sequential nonce manager.

schnorr

Schnorr signatures over the ECgFp5 curve, with Poseidon2 as the binding hash.

tx

Lighter L2 transaction encoding.