PHARMCHAIN: A BLOCKCHAIN-ENABLED FRAMEWORK FOR PHARMACEUTICAL SUPPLY CHAIN TRANSPARENCY AND COUNTERFEIT MEDICINE PREVENTION

Abstract

The global pharmaceutical supply chain confronts a critical crisis of substandard and falsified medicines, with the World Health Organization estimating that over 10% of medicines in low- and middle-income countries are counterfeit or substandard, causing an estimated 500,000 deaths annually. This paper presents PharmChain — a novel, permissioned blockchain framework on Hyperledger Fabric v2.4 — integrating distributed ledger technology, smart contracts, Internet of Things (IoT) cold-chain sensors, and QR-code drug serialization. The primary contribution is the Hierarchical Proof-of-Authority (HPoA) consensus mechanism, fully specified with four-phase algorithmic pseudocode, formal safety and liveness proofs (Theorems 1–3), Byzantine fault-tolerance bounds (f < ⌊(m−1)/3⌋ for m Tier 2 validators), and message complexity analysis (O(m²+mk) ≈ O(n)). Smart contracts were formally verified using NuSMV model checking and TLA+ specification, resolving 3 unauthorized state-transition vulnerabilities and 2 integer overflow vulnerabilities. Reproducible experimental evaluation — validated by paired t-tests (p < 0.05) and 95% confidence intervals across 10 independent trials on a 20-node testbed — demonstrates peak throughput of 2,847 ± 112 TPS (block_size=100, tx_payload=512B, BatchTimeout=1s), mean latency of 1.3 ± 0.2 s, and counterfeit detection accuracy of 99.5% across 50,000 pharmaceutical transactions. Dedicated security evaluation across 1,900 attack scenarios confirms resistance to Sybil, replay, double-spend, insider, smart contract manipulation, and node compromise attacks. All experimental artifacts are publicly available at https://github.com/kanagasankariathimoolam/Blockchain-Pharma. PharmChain outperforms MediLedger, DrugLedger, and PHTrack on all evaluated metrics.