Abstract:The cross-chain technology addresses the issue of information silos between the blockchains of different enterprises in the aquatic product supply chain. However, there is a risk of privacy leakage during cross-chain transactions. To enhance the security and privacy of cross-chain transactions for aquatic products, based on the business processes of aquatic product transactions and existing cross-chain technologies, a cross-chain transaction model for aquatic products was proposed by using sidechains. The model designed an interoperation process for assets between the main chain and sidechains, and a two-way anchoring of assets between the main chain and sidechains was implemented through smart contracts. Based on the characteristics of aquatic product cross-chain transactions, the model designed the data structure and transaction process for cross-chain data. A three-phase commit protocol was used to ensure data consistency in cross-chain transactions, improve the transaction success rate, and refine the handling process for transaction failures. Additionally, to address the potential double-spending issue introduced by sidechains, a monitoring method was adopted for control. Finally, a prototype system for cross-chain transactions of aquatic products using sidechains was implemented on the Hyperledger Fabric platform. The system architecture was structured with dedicated functional modules to support secure asset transfer, cross-chain data validation, and coordinated transaction management across participating enterprises, ensuring robustness and operational efficiency. Experimental results showed that this model effectively prevented the exposure of private keys when connecting the main chain to cross-chain operations, reducing the risk of privacy leakage. Under high transaction volumes, the average transaction success rate remained consistently above 99%, and the average transaction delay remained below 0.3s. Furthermore, by using sidechains to offload the query pressure on the main chain, parallel query tests with over 10 000 data points demonstrated a query efficiency improvement of approximately 35%.