Oblivious transfer with timed-release receiver’s privacy

Oblivious transfer (OT) is an important primitive used in many cryptographic protocols. According to the traditional OT’s security requirements, the privacy of the receiver is protected forever, which, however, limits the applications of OT in some areas. In this paper, we propose a new OT with timed-release receiver’s privacy in which the sender has N messages, of which the receiver can choose to receive one or more, in such a way that (a) the receiver only learns about the requested messages, and (b) the sender learns the receiver’s selections after a designated time. Thus the receiver’s privacy is just protected within a period of time. Besides, we also present a concrete scheme combining Tzeng’s OT scheme with Casassa Mont et al.’s timed-release encryption scheme.