A Blockchain‐Based Privacy Protection Scheme for Bidding Transactions Supporting Threshold Traceability

Bidding transactions are widely used in scenarios such as government procurement and corporate tendering. However, while traditional blockchain achieves transparency in transactions, it also poses a risk of sensitive information such as bidder identity, quotation, and time being leaked, thereby undermining the fairness and compliance of bidding. Addressing the challenge of the incompatibility between strong anonymity and regulatory compliance in existing blockchain privacy protection schemes, this paper proposes a blockchain bidding privacy protection scheme with threshold traceability based on the bidding transaction scenario. Firstly, our scheme constructs a permissioned ring signature structure based on qualification verification, achieving strong identity anonymity while ensuring the validity of anonymous aggregation. By introducing a time‐lock commitment mechanism and a zero‐knowledge timeliness verification mechanism, it ensures the confidentiality of bidding content while guaranteeing that the submission is completed before the deadline, thereby achieving verifiable temporal compliance. To balance privacy protection and regulatory compliance, this paper designs a (t, n) threshold traceability mechanism based on Shamir's secret sharing, which fragments the master key among multiple regulators. Only through multi‐party collaborative authorisation can the identity of non‐compliant bidders be revealed, thereby reducing the risk of regulatory abuse. Security analysis proves that this scheme meets security requirements such as unforgeability, bidding privacy, and policy integrity under standard cryptographic assumptions. Extensive experimental results indicate that the proposed scheme achieves competitive performance in terms of privacy preservation and traceability compared with existing schemes.