Groups Design Goals

• Users should be able to create any number of groups without limitation.

• Group creator is the group's super admin and he must authorize any new group member and can at any time remove a member from a group.

• Super admin should be able to invite new users to the group, remove existing users from the group and accept or reject requests to join the group from users.

• A group member should be able to leave the group at any time.

• Super admin should be able to assign admin right to one more other group member.

• Only group members should be able to read group messages and write messages to the group.

• Support large scale gorups: More than 256 members and up to 10,000 members.

Privacy Requirements

• Only group members should be able to see the id of other group members. Non-group members should not be able to see the group members.

• The only personally identifying information shared by group members is voluntarily information shared by a member about himself.

• Groups should provide high-degree of both forward and backward secrecy to group messages.

Groups and Status Feeds

Groups are somewhat similar to status feed with the following differences:

1. A group member (and only a group member) can send a message to all other group members.
2. A group member (and only a group member) can reply to any group message (threaded discussion).