Privacy-preserving publish/subscribe service in untrusted third-party platform

Nowadays, many organizations or corporations, such as banks, hospitals, schools, etc., use third-party platform to send notifications or information to their customers or users. This communication model can be generalized to the publish/subscribe model. The publisher will send the content to the subscriber whenever there is any new content that matches the interest of the subscriber. However, the content may contain users' privacy which is sent in plain text by the third-party platform. When the platform is not fully trusted, users' privacy is at the risk. In this paper we propose a secure protocol to protect users' privacy against the untrusted third-party platform. Our privacy preserving protocol has three main advantages: 1) There is no need to set up a secure synchronous communication channel between the subscriber and the publisher in our protocol. 2) There is no need to introduce any Certificate Authority (CA) for certifying publishers or subscribers in our protocol. 3) There is no need for subscribers or publishers to remember any additional key for each subscription or publication, which makes our protocol scalable to large pub/sub system.