Efficient and Adaptive Procurement Protocol with Purchasing Privacy
A procurement protocol is a protocol for a buyer to purchase digital goods at their prices from a vendor and its privacy preservation can be achieved by priced oblivious transfer (POT). POT allows the buyer to obliviously procure items one by one. An adaptive POT protocol only consumes O(1) communication cost in each transaction. However, we found that the state-of-the-art adaptive POT protocol is less practical and does not meet real-world needs. It restricts only one buyer and the vendor must encrypt all the items for each buyer in the multi-buyer setting. Besides, it has to employ computationally expensive primitives such as zero-knowledge proof. It is therefore unscalable and unsuitable in large-scale applications. In this paper, we propose an efficient adaptive priced oblivious transfer protocol to address the aforementioned problems. The proposed adaptive POT is built on top of a new cryptographic primitive, namely, adaptive set membership encryption (ASME). In our proposed protocol, all items are encrypted without the use of buyers & #x0027; public keys and hence they can be used for universal buyers. Our protocol significantly reduces the transaction cost compared to existing schemes. The implementation shows that our protocol is efficient in terms of bandwidth and computational cost.