This book introduces a frame work using Lagrange Interpolation is developed for key distribution and asynchronous group key agreement. The major contribution is on security services like confidentiality and authentication in group communications. The major contribution in this book is aiming at providing the technical background in learning the development of group key agreement mechanisms. First chapter will give the glimpses of the need of key management and the role of the security. Next two chapters discuss about background of group key management. Afterwards new group key agreement mechanisms and its security analysis against different attacks. The last two chapters talk about a new protocol based on Lagrange interpolation.