Paper 2026/1262 Original: eprint.iacr.org/2026/1262 ↗

PQ-SMS: A Post-Quantum Sanitizable Multi-Signature Scheme for Satellite PKI

Abstract

Satellite communication systems, as critical long-lifecycle infrastructure, face a dual security challenge in the coming decades: the threat of quantum computers and the operational rigidity of traditional Public Key Infrastructure (PKI). While migrating to Post-Quantum Cryptography (PQC) addresses the former, it fails to solve the inefficiency of certificate management, where in-orbit policy updates require a prohibitively slow and complex multi-party re-issuance process. To address these challenges, we introduce the concept of a Post-Quantum Sanitizable Multi-Signature ($\texttt{PQ-SMS}$), a novel primitive that enables controlled certificate adaptation across hierarchical trust while preserving the integrity of the root of trust. Building on this, we present $\texttt{Sat-APCS} $($\textbf{Sat}$ellite $\textbf{A}$daptable $\textbf{P}$ost-quantum $\textbf{C}$ertificate $\textbf{S}$cheme), which cryptographically decouple a certificate's immutable, multi-signed identity from its dynamic operational policies. This allows a delegated entity to perform lightweight, in-orbit policy updates while the foundational signature from the original consortium of authorities remains unchanged and valid. We instantiate $\texttt{PQ-SMS}$ based on the NIST-standard CRYSTALS-Dilithium signature and a ISIS-based chameleon hash, and prove its security under standard lattice assumptions. Furthermore, Performance evaluation demonstrates that $\texttt{PQ-SMS}$ bypasses the interactive re-signing loop of traditional PKI, achieving an order-of-magnitude reduction in update bandwidth.