An Evidence-Preserving Migration Model for Post-Quantum Permissioned Supply-Chain Ledgers: Certificate Referencing and Checkpoint Anchoring

Permissioned blockchains increasingly record provenance for medicines, aircraft parts and food, and many of those records must stay verifiable for decades.The signatures that bind them to their authors rest on RSA and elliptic-curve assumptions that a large fault-tolerant quantum computer would break.Existing work concentrates on which post-quantum algorithm to use and how large its keys and signatures are.Two practical questions for a live ledger receive less attention: how long each class of record can safely wait for migration, and how evidence signed classically can remain trustworthy after the classical scheme falls.This paper proposes an evidence-preserving migration framework for Hyperledger Fabric-style networks.Its elements are (i) a retention-aware risk model that ranks assets by migration slack, (ii) policy epochs that move the network through classical, hybrid and post-quantum verification modes by configuration transaction, with a hybrid signature that binds epoch and certificate reference to resist downgrade and substitution, (iii) an on-ledger certificate registry that lets a transaction carry a 32-byte digest instead of a full certificate, and (iv) periodic post-quantum-signed Merkle checkpoints that anchor historical blocks.Using only published parameter sizes, we derive an analytical model: for ML-DSA-65 in hybrid mode, certificate referencing lowers modelled signature-related bytes per transaction from about 27.5 KB to about 10.2 KB (a 63% reduction) for a client and two endorsers, while checkpoint storage is negligible by comparison.An evaluation protocol is specified.This paper reports the design, the analytical model and the evaluation methodology; empirical measurements are reserved for the implementation phase and are not claimed here.