Files
corona/papers/lp-073-pulsar/lp-073-pulsar-resharing.tex
zeekay 261ad9d290 pulsar: lattice threshold kernel with key-era lifecycle + Pulsar-SHA3 + Nebula binding
Forked from github.com/luxfi/corona @ d09b2c2. Pulsar inherits the
2-round signing math byte-equal but adds blockchain-grade key
lifecycle and a SHA3-based domain-separated hash profile for
permissionless validator-set rotation.

Inherits from upstream Corona (byte-equal):
  - Sign1/Sign2/Combine 2-round signing math
  - Lattice ring R_q = Z_q[X]/(X^256+1), q = 0x1000000004A01
  - Module-LWE / Module-SIS hardness
  - NTT, Discrete-Gaussian Ziggurat, MAC layer

Replaces from upstream:
  - Broken Feldman-style DKG (pseudoinverse-recoverable). Replaced
    with: (a) one-time foundation MPC ceremony / trusted-dealer
    Bootstrap; (b) Pedersen DKG over R_q (research, dkg2/) hiding
    under MLWE on B / binding under MSIS on [A | B].
  - Trusted-dealer-per-epoch lifecycle (wrong shape for permissionless
    rotation). Replaced with Verifiable Secret Resharing (VSR) every
    epoch under the persistent group public key.

Key-era lifecycle (KeyEraID / Generation / RollbackFrom):
  - KeyEraID bumps only at Reanchor (rare governance event)
  - Generation bumps every Refresh / Reshare under the same GroupKey
  - RollbackFrom records prior generation reverted from (0 = forward)
  - Activation cert (QUASAR-PULSAR-ACTIVATE-v1) gates new generations
    under the unchanged GroupKey

Pulsar-SHA3 hash profile (NIST FIPS 202 / SP 800-185):
  - Hc:        cSHAKE256("PULSAR-HC-v1", transcript) → challenge
  - Hu:        cSHAKE256("PULSAR-HU-v1", transcript) → XOF stream
  - TranscriptHash: TupleHash256("PULSAR-TRANSCRIPT-v1", parts...)
  - PRF:       KMAC256(key, msg, "PULSAR-PRF-v1")
  - MAC:       KMAC256(key, msg, "PULSAR-MAC-v1")
  - Pairwise:  KMAC256(kex, encode(...), "PULSAR-PAIRWISE-v1")
  - Default suite is Pulsar-SHA3; Pulsar-BLAKE3 retained as optional
    non-normative fast profile. HashSuiteID is bound into transcripts.
  - Implementation at pulsar/hash/ with HashSuite interface.
  - All KATs regenerated under SHA3 profile; vectors in
    luxcpp/crypto/pulsar/test/kat/.

Nebula root binding (TranscriptInputs + ActivationMessage canonical
bytes, all bound under TupleHash256):
    chain_id, network_id, group_id,
    key_era_id, old_generation, new_generation,
    old_epoch_id, new_epoch_id,
    old_set_hash, new_set_hash,
    threshold_old, threshold_new,
    group_public_key_hash,
    nebula_root,
    hash_suite_id,
    implementation_version,
    variant.

Packages:
  primitives/   Shamir over R_q, Lagrange, hash helpers
  sign/         2-round sign math (byte-equal upstream)
  threshold/    GroupKey, KeyShare, Signer types
  reshare/      VSR kernel — Refresh (HJKY97 zero-poly), Reshare
                (Desmedt-Jajodia), commit (Pedersen R_q), complaint,
                transcript, pairwise KEX, activation cert
  hash/         HashSuite interface; PulsarSHA3 (default), PulsarBLAKE3
  dkg2/         Pedersen DKG over R_q (research, reference only)
  keyera/       Lifecycle wrapper: Bootstrap → Reshare → Reanchor
  papers/       LP-073-pulsar paper (sections + bibliography)
  cmd/*_oracle/ KAT generators (Go ↔ C++ byte-equal validation)

DESIGN.md is the single source of truth:
  - The Pulsar metaphor (rotating beam over persistent body)
  - Vocabulary stack per LP-105: Nebula / Photon / Lumen / Beam /
    Pulsar / Pulse / Prism / Horizon / Quasar
  - Pulsar ≠ Lumen (PQ stream is separate, planned)
  - Pulsar / Lens / LSS three-layer architecture
  - Bootstrap Dealer vs Signature Coordinator
  - No-slashing failure ladder (timeout → retry → rollback → reanchor)
  - MVP VSR vs Robust VSR phasing
  - Borrowed-brand terms ("X-Wing" used casually) replaced with
    "hybrid KEM" / "Hybrid Lumen Handshake"; X-Wing cited only as
    the IETF combiner primitive name where exact reference matters.

Tests: full suite green
  hash 5+/5+, keyera 5/5, reshare 45+/45+, threshold, sign, dkg,
  dkg2, primitives, networking, utils, corona_oracle_v2 KAT —
  all pass.

Honest claim: the crypto primitives are not new (HJKY97,
Desmedt-Jajodia97, Wong-Wang-Wing02, Corona, Hermine, Threshold
Raccoon all exist). The novel contribution is the systems
composition: a permissionless-consensus deployment architecture that
turns static two-round PQ threshold signatures into a dynamic,
leaderless, validator-rotation-tolerant finality layer.

Companion docs: papers/lp-073-pulsar/ (academic paper); LP-073 +
LP-103 + LP-105 in github.com/luxfi/lps; threshold/protocols/lss/
lss_pulsar.go (LSS adapter wrapping this kernel).
2026-03-03 12:00:00 -08:00

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% Standalone wrapper to compile the resharing section.
% The full LP-073-pulsar paper is composed at ~/work/lux/papers/lp-073-pulsar/
% (parent directory under lux/papers/); this minimal wrapper exists so
% the section can be typechecked in isolation during development.
%
% Compile with: pdflatex lp-073-pulsar-resharing.tex (twice, for refs).
\documentclass[11pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath,amssymb,amsfonts,amsthm}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage{booktabs}
\usepackage{algorithm}
\usepackage{algpseudocode}
\usepackage{enumitem}
\usepackage{cleveref}
\hypersetup{colorlinks=true,linkcolor=black,citecolor=blue,urlcolor=blue}
\newtheorem{theorem}{Theorem}
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{remark}{Remark}
\title{LP-073-pulsar: Proactive Secret Resharing for Pulsar Lattice Threshold Signatures}
\author{Lux Industries Inc}
\date{\today}
\begin{document}
\maketitle
\begin{abstract}
We adapt the Herzberg-Jakobsson-Jarecki-Krawczyk-Yung 1997 proactive
secret-sharing protocol to the lattice ring $R_q = \mathbb{Z}_q[X]/(X^{256}+1)$
used by Pulsar lattice threshold signatures, allowing the validator-set
rotation problem of Quasar consensus to be solved without re-running
trusted-dealer key generation at every epoch boundary. The master secret
$s$ is preserved across rotations; only the share distribution changes.
The genesis-time public key $\tilde b$ is unchanged, so signatures from
any future epoch verify under the same public anchor.
\end{abstract}
\input{sections/06-resharing}
\begin{thebibliography}{99}
\bibitem{hjky97}
Amir Herzberg, Markus Jakobsson, Stanis\l{}aw Jarecki, Hugo Krawczyk, Moti Yung.
``Proactive secret sharing or: How to cope with perpetual leakage.''
\emph{CRYPTO 1995/1997}.
\bibitem{desmedt-jajodia97}
Yvo Desmedt, Sushil Jajodia.
``Redistributing secret shares to new access structures and its applications.''
Technical Report ISSE TR-97-01, George Mason University, 1997.
\bibitem{shamir79}
Adi Shamir.
``How to share a secret.''
\emph{Communications of the ACM} 22(11):612--613, 1979.
\bibitem{wong02}
Theodore M.\ Wong, Chenxi Wang, Jeannette M.\ Wing.
``Verifiable secret redistribution for archive systems.''
In \emph{Proceedings of the First International IEEE Security in Storage Workshop}, 2002.
\bibitem{lp020}
LP-020. ``Quasar Consensus: Triple-Sign with BLS, Corona, and ML-DSA.''
\bibitem{lp070}
LP-070. ``ML-DSA-65 Identity Layer for Quasar Validators.''
\bibitem{lp073}
LP-073. ``Corona: A Two-Round MAC-Authenticated Lattice-Based Threshold Signature.''
\end{thebibliography}
\end{document}