  Blockchain offers traceability and transparency to supply chain event data
and hence can help overcome many challenges in supply chain management such as:
data integrity, provenance and traceability. However, data privacy concerns
such as the protection of trade secrets have hindered adoption of blockchain
technology. Although consortium blockchains only allow authorised supply chain
entities to read/write to the ledger, privacy preservation of trade secrets
cannot be ascertained. In this work, we propose a privacy-preservation
framework, PrivChain, to protect sensitive data on blockchain using zero
knowledge proofs. PrivChain provides provenance and traceability without
revealing any sensitive information to end-consumers or supply chain entities.
Its novelty stems from: a) its ability to allow data owners to protect trade
related information and instead provide proofs on the data, and b) an
integrated incentive mechanism for entities providing valid proofs over
provenance data. In particular, PrivChain uses Zero Knowledge Range Proofs
(ZKRPs), an efficient variant of ZKPs, to provide origin information without
disclosing the exact location of a supply chain product. Furthermore, the
framework allows to compute proofs and commitments off-line, decoupling the
computational overhead from blockchain. The proof verification process and
incentive payment initiation are automated using blockchain transactions, smart
contracts, and events. A proof of concept implementation on Hyperledger Fabric
reveals a minimal overhead of using PrivChain for blockchain enabled supply
chains.
