  A fundamental concern of any secure group communication system is key
management and wireless environments create new challenges. One core
requirement in these emerging networks is self-healing. In systems where users
can be offline and miss updates, self-healing allows a user to recover lost
session keys and get back into the secure communication without putting extra
burden on the group manager. Clearly, self-healing must only be available to
authorized users. This paper fixes the problem of collusion attack in an
existing self-healing key distribution scheme and provides a highly efficient
scheme as compared to the existing works. It is computationally secure, resists
collusion attacks made between newly joined users and revoked users and
achieves forward and backward secrecy. Our security analysis is in an
appropriate security model. Unlike the existing constructions, our scheme does
not forbid revoked users from rejoining in later sessions.
