A novel mathematical model for group communication with trusted key generation and distribution using shamir´s secret key and USB security

Authentication and confidentiality are two sides of a coin. A group communication is said to be secure only if it preserve both authentication and confidentiality. A group communication is secure if every member of the group is a trusted person. Hence, individual security leads to group security. This paper proposes a new method for secure group communication by providing individual security, in which each group is assigned with a one-time session key. In order to maximize individual security each user uses USB key together with his user name and password. This paper make use of shamir´s secret sharing algorithm for creation of the share for each member of the participating group in communication, and Lagrangs interpolation formula for construction of key for the share by each member in the group. The proposed protocol is able to resist both insider and outsider attack.