In this paper, we introduce a new cryptographic primitive called broadcast encryption with dealership. This notion, which has never been discussed in the cryptography literature, is applicable to many realistic broadcast services, for example subscription-based television service. Specifically, the new primitive enables a dealer to bulk buy the access to some products (e.g., TV channels) from the broadcaster, and hence, it will enable the dealer to resell the contents to the subscribers with a cheaper rate. Therefore, this creates business opportunity model for the dealer. We highlight the security consideration in such a scenario and capture the security requirements in the security model. Subsequently, we present a concrete scheme, which is proven secure under the decisional bilinear Diffie–Hellman exponent and the Diffie–Hellman exponent assumptions.

As wireless networks flourish, Internet users can access social network platforms (such as Facebook and Twitter) through personal electronic devices anywhere and anytime. However, because users often deploy social network platforms in a public network setting, a common concern remains about how to guarantee privacy for photo sharing. Although most platforms aim to protect such privacy, few are able to reach the goal. This work focuses on an interesting potential privacy risk, called the deletion delay of photo sharing, by pinpointing and investigating the risk's existence in some well-known social network platforms.

The issue of empowering patients to be well informed with regards to their health records has been well accepted in the community, which is known as the Personal Health Record (PHR). PHR has been believed as the solution for better management of an individual’s health, and as the tool that will empower the patient in correlation with healthcare providers through the ability to provide his/her own medical history. In this work, we aim to take one step further by equipping patients with the ability to “control” the access to their PHR efficiently and easily, by incorporating the emerging cloud technology. Specifically, we aim to provide the patients with the luxury of using the power of the cloud to conduct the outsourced work efficiently. To realize this, we present the notion of online/offline ciphertext-policy attribute-based proxy re-encryption scheme, which is very useful primitive in empowering personal health records in cloud computing. We present such a notion as well as a set of security requirements. More specifically, we define two security models covering both outsider and insider attacks. Furthermore, we present a concrete construction of such a scheme, and prove that it is secure under the well known complexity assumptions and following our security models.