Instead the group admin sends this message to the server, the server verifies if he is actually an admin and then it instructs group members for key exchange. It should have but they went out of specifications. Everything happens exactly that way except the fact that there is no admin in Signal and every member can send group management message to the group members.īut In WhatsApp, a group admin doesn't send group management message directly to the group members. In Signal app, server doesn't involve with group administration. That's why it is very important to flush old group keys when someone leaves because former member has learnt group keys of every member. Each member has its own group key and everybody keeps list of group keys of each other. Yet another time, key exchange can be seen. Once that person is added, he generates his own group key and sends to every member of the group as a personal one-to-one pairwise encrypted message. This is where you see that message on GUI. This group management message also notifies the members visually so that they know that said person is now part of the group. Now if you observe the key exchange is already started to happen. To add a member into a group, the group administrator sends a group management message to each group member which instructs them to send their own group key to the person group admin wants to add. It is because the group key exchange would still be visible.

While what's app if pressurised by the government can choose to program it in a way that no message is shown on GUI if they add an infiltrator.īut that won't prevent the infiltrator from getting detected. Signal is open-source so you can verify from the source that a message that someone has joined the group is shown on GUI. But without letting the group to be notified, It's not possible well atleast in Signal protocol. It is possible for a server admin to silently add an infiltrator to group chats.

Signal group chat encryption