The Online Social Network (OSN) facilitates users’ openness to a wider audience and social circles, which was not possible before its invention. However, this freedom of social expression and sharing of personal information may lead to violate the privacy of an individual and content. OSN has issue of privacy protection, which can be data about a user or the contents shared by user, especially in a group communication. The primary objective of this research work is to protect the privacy of the contents that are shared within the group. In general, OSN’s group communication can be divided into Open Group and Closed Group. In an Open Group, the contents are shared among the group members and further sharing is allowed. On the other hand, in Closed Group the contents are shared among the group members only. In Open Group, the problem with OSN is that once the content is shared, the data owner or co-owner has no control over its further distribution. Thus we provide a framework for collaborative content sharing which transfers the control of data dissemination from the service providers to data owner or co-owner. In the proposed framework, an Access Management Server (AMS) is introduced as a middleware to interact with the OSN server and manages users. The AMS encrypts the content before uploading to the OSN server and creates secret shares of the encryption key that can be used for the authorization of a co-owner to the content. Similarly, further sharing of content with other users (Viewers) is allowed with the consent of threshold number of co-owners provided by the data owner. In Closed Group, the content is shared within the group members only, and no further sharing is allowed. The group communication can be secured using the cryptographic techniques, but group key management is a problem, especially in case of untrusted server. This work provides, a Scalable Group Key Management Protocol (SGKMP) to generate the shared group key and its procedure for modification in case a user leaves or joins the group. The key setup phase of the proposed protocol requires two rounds to complete it irrespective of group size, in contrast to the existing protocols that need n rounds to achieve it, where n is the total number of users in the group. Similarly, the protocol is scalable enough to update key by even a single group member without involving all group members.