Keychat's second implementation of encrypted group chat is termed "shared key group," which will be discontinued in the next release.
Within a shared key group, a single encryption key is shared among all participants. Members encrypt their messages using this common key before sending, and others decrypt using the same key upon reception.
This setup fails to meet the third and fourth requirements previously outlined.
If a member who has compromised the group's confidentiality needs to be removed, fundamentally, a new group must be created. The group administrator must individually communicate the new shared key to each member of the new group, denoted as N, the number of participants. This illustrates a significant drawback of the shared key group: the inefficiency in dynamically updating its members.
Visualizing the five types of end-to-end encrypted group chats as a spectrum, the pairwise group occupies the most secure position, while the shared key group is positioned at the least secure end.
Initially, Keychat tested both extremes of this spectrum before proceeding to explore the intermediate options.
