Biblio

Due to the rapid development of internet in our daily life, protecting privacy has become a focus of attention. To create privacy-preserving database and prevent illegal user access the database, oblivious transfer with access control (OTAC) was proposed, which is a cryptographic primitive that extends from oblivious transfer (OT). It allows a user to anonymously query a database where each message is protected by an access control policy and only if the user' s attribute satisfy that access control policy can obtain it. In this paper, we propose a new protocol for OTAC by using elliptic curve cryptography, which is more efficient compared to the existing similar protocols. In our scheme, we also preserves user's anonymity and ensures that the user's attribute is not disclosed to the sender. Additionally, our construction guarantees the user to verify the correctness of messages recovered at the end of each transfer phase.

Major online messaging services such as Facebook Messenger and WhatsApp are starting to provide users with real-time information about when people read their messages, while useful, the feature has the potential to negatively impact privacy as well as cause concern over access to self. We report on two surveys using Mechanical Turk which looked at senders' (N=402\vphantom\\ use of and reactions to the `message seen' feature, and recipients' (N=316) privacy and signaling behaviors in the face of such visibility. Our findings indicate that senders experience a range of emotions when their message is not read, or is read but not answered immediately. Recipients also engage in various signaling behaviors in the face of visibility by both replying or not replying immediately.