Design and Evaluation of a Privacy-preserving Supply Chain System Based on Public Permissionless Blockchain

Securing the traceability of products in a supply chain is an urgent issue. Recently, supply-chain systems that use a blockchain have been proposed. In these systems, the blockchain is used as a common database shared among supply chain parties to secure the integrity and reliability of distribution information such as ownership transfer records. These systems thus secure a high level of traceability in the supply chain. Considering future scalability of supply chains, public permissionless blockchain (PPBC) is a promising approach. In this approach, however, distribution information that should be kept private is made public since the information recorded in PPBC can be read by anyone. We therefore propose a method for preserving privacy while securing traceability in a supply chain system using PPBC. The proposed method preserves privacy by concealing distribution information via encryption. In addition, the proposed method ensures distribution among legitimate supply chain parties while concealing their blockchain addresses by using zero-knowledge proofs.We implement the proposed method on Ethereum smart contracts and verify the system behavior. The results show that the proposed method works as expected, and that system usage cost per distribution party is at most 2.2 × 106 gas units in terms of blockchain transaction fees.