ISSN 1000-1239 CN 11-1777/TP

Journal of Computer Research and Development ›› 2017, Vol. 54 ›› Issue (10): 2215-2223.

### An Efficient Single Server-Aided k-out-of-n Oblivious Transfer Protocol

Zhao Shengnan1, Jiang Han1, Wei Xiaochao2, Ke Junming1, Zhao Minghao1

1. 1(School of Computer Science and Technology, Shandong University, Jinan 250101); 2(School of Information Science and Engineering, Shandong Normal University, Jinan 250358)
• Online:2017-10-01

Abstract: Oblivious transfer (OT) is a cryptographic primitive used for choice information hiding for the receiver. As a basic tool for high-level multi-party cryptographic protocol construction, it plays an important role in numerous specific applications. In the k-out-of-n OT(OT\+k\-n), the receiver acquires k selections among the n choice in an oblivious manner. Generally, the construction of the OT\+k\-n involves lots of group exponential operations, which brings a heavy burden for embedded devices with limited computational capabilities. With the proliferation of cloud computing, it is feasible to implement complex cryptographic primitives with the support of powerful computing recourse and high-speed dedicated network provided by the cloud service provider (CSP). In this paper, we propose a service-assisted k-out-of-n OT protocol in single server architecture, which outsources the vast majority of exponentiation operations to the cloud. This scheme is constructed with secret sharing and other fundamental public-key primitives, and it achieves provable security on none-collusion semi-honest model under the decisional Diffie-Hellamn (DDH) hard problem; meanwhile it ensures data privacy against the cloud server. Besides, a detailed description of scheme construction and security proof is presented in the context. As a basic cryptographic primitive in cloud environment, the single server-added oblivious transfer protocol will play an important role in designs of general cloud-assisted multi-party computation protocol as well as developments of secure and efficient cloud service software.

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