Abstract: This paper proposes a multi-blockchain food supply chain traceability system (MBFST) based on the integration of consortium blockchain and private blockchain, to address challenges in food traceability. Enterprises carry out business cooperation through the consortium blockchain system, and record the trade circulation through the private blockchain system. The cross-chain interaction protocol between the private blockchain and the consortium blockchain is designed to implement the interaction and mapping according to the traceability ID. The system enables business cooperation and trade circulation recording through the consortium and private blockchain, respectively, with a cross-chain interaction protocol facilitating interaction and mapping based on traceability ID. Through data isolation mechanism like private data set, the protection of private data of enterprises is ensured. Experimental results show that the prototype system can achieve accurate traceability among enterprises in the food supply chain and ensure the whole process traceability both on-chain and off-chain. MBFST achieves a maximum TPS (transaction per second) of over 1000 and a TPS of over 200 for rich queries using traceability ID, with an average delay stable at 0.2～0.3 s. MBFST has superior query performance in high concurrency circumstances in terms of traceability, privacy and efficiency.

Key words: blockchain, consortium blockchain, private blockchain, supply chain traceability, cross-chain interaction, privacy protection