Secure Sealed-Bidding Networks via Conditional Time-Aware Access Authorization

A sealed-bidding network is a critical infrastructure in modern government and industry, enabling efficient transactions between bidders and tenderees. To prevent the tenderees from accessing bidding documents not intended for them, cryptographic access control is often adopted in the bidding network. However, it is vulnerable to malicious bidders who may submit invalid bids or attempt to manipulate the bidding process. Besides, existing cryptographic access control mechanisms lack binding between bidding documents and their opening time, leading to unfair advantages where tenderees may disclose bidding documents to favored bidders. In this paper, we introduce BiTEA, a novel sealed-bidding network supporting Bilateral Time-aware Access control. BiTEA ensures successful access only when both the bidders and the tenderees satisfy the conditions after the specified bid opening time. To instantiate BiTEA, we propose a cryptographic primitive named timed-release identity-based matchmaking encryption (TIME), which builds upon an identity-based setting and incorporates an independent time decryption key. TIME is proved to be secure under the BDH assumption in the random oracle model. We present a detailed BiTEA design from TIME, establishing bilateral access control which also supports message privacy, ciphertext authenticity and time control. Performance evaluations demonstrate that BiTEA is cost-effective with a time cost of 0.08 s to access a 256-byte encrypted bidding document.