A secure group communication using non-interactive key computation in multiparty key agreement

Broadcast encryption deals with broadcasting an encrypted message, so that only a set users termed privileged can decrypt it. These privileged set can be formed by selecting t users among n users within the group. To make sure that the data is available only to privileged users in the group the secret key is used which is known only to members of privileged set at any instant of time. Using secret key sender encrypt the data and sends, receiver in turn decrypts it. This privileged set is known as secure group, communication within the set as secure group communication. Since, the secure group is dynamic in nature, members in the group may change over time, i.e., new members may join the group and existing members may leave the group. As group membership changes key must be changed and redistributed securely to all authorized users. This type of communication provides only confidentiality. Providing authentication in addition to confidentiality is an important issue in secure group communication. A protocol is designed for authentic broadcast encryption. Authentication scheme used is a multiparty authentication scheme which allows all the users in the system to send and receive message simultaneously. Since, all the group members in the system can send and receive message, the sender of the message must be able to indicate his identity and the receiver must be able to verify the authenticity of the message. To verify the authenticity the key is formed by non-interactively with the help of information obtained by key distribution center (KDC). This scheme is secure against colluding malicious parties numbering more than k (threshold). This scheme provides authenticity by using a part of information keys which is used for secret key computation, thus without increasing the storage at the user.