A Phased Hybrid Migration Framework for Post-Quantum Cryptography in Existing Permissioned Blockchain Supply-Chain Systems

Enterprise supply chains increasingly record shipments, certificates and ownership transfers on permissioned blockchains, and many of these records must stay verifiable for ten to twenty years.The signatures that protect them, however, rest on RSA and elliptic-curve assumptions that a large fault-tolerant quantum computer would break.Although NIST has now published standards for lattice-based and hash-based post-quantum schemes, operators of live ledgers still lack a tested route for adopting them without halting business.This paper proposes a five-phase migration framework for Hyperledger Fabric-style networks.Its core elements are (i) a cryptographic abstraction layer that isolates algorithm choice from ledger logic, (ii) a policy-epoch mechanism that moves the network through classical, hybrid and post-quantum verification modes by means of ordinary configuration transactions, (iii) a dual-stack identity design that lets organisations rotate keys at their own pace, and (iv) a migration orchestrator that tracks readiness and supports rollback.We formalise the problem and the threat model, give a hybrid signature construction with explicit downgrade protection, derive an analytical model of per-transaction and storage overhead from the published parameter sizes of the standardised schemes, and specify an experimental protocol for measuring latency, throughput, size and resource cost.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.