One of the major features we introduced in the TextSecure v2 release was private group chat. We believe that group chat is an important feature for encrypted communications projects, so we wanted to try to summarize some of the existing work in this area, as well as how TextSecure’s group chat protocol functions.
read more........https://whispersystems.org/blog/private-groups/
read more........https://whispersystems.org/blog/private-groups/