P3Q-FRI Low-Degree Test
FRI (Fast Reed-Solomon Interactive Oracle Proof) low-degree test specification for the P3Q STARK substrate.
Abstract
P3Q-FRI is the FRI (Fast Reed-Solomon Interactive Oracle Proof of
Proximity) low-degree test used by the LP-4800 Plonky3-fork STARK
substrate (historically called "P3Q core" — see LP-4800 §"Slot
history"). This LP pins the FRI parameter set for the strict-PQ
profile: the blowup factor (target 4-8x), the folding arity (2 or
4), the number of FRI queries (target 80-100 for 100-bit soundness),
the round-by-round Fiat-Shamir derivation rule (binding to
LP-4810's cSHAKE256 transcript), and the terminal polynomial degree
bound. Soundness is analyzed in the random-oracle model under the
list-decoding regime per the SCALE / DEEP-FRI / Plonky3 line of
work; concrete soundness numbers will appear in a subsequent
revision once the field and blowup are finalized. The verifier is
implemented as part of the STARK-FRI verifier at placeholder slot
0x012220 (pending LP-221 dedicated spec) — originally a branch of
the precompile at 0x012205 per the pre-2026-06-03 design;
relocated on 2026-06-03 per LP-218 §"Slot history: STARK-FRI rename"
when 0x012205 was reassigned to the unified P3Q verifier family
(LP-218 / LP-220). Verification consumes ~5-10 ms (LP-0120).
Reference implementation
- Primitive:
luxfi/p3q/fri(planned) - Hash binding: LP-4810
Copyright
Copyright and related rights waived via CC0.