This documents describes the group chat protocol used by the status application. Pairwise encryption is used among member so a message is exchanged between each participants, similarly to a one-to-one message.
Membership updates messages are used to propagate group chat membership changes. The protobuf format is described in the [Status Payload Specs](status-payload-specs.md). Here we will be describing each specific field.
The protobuf messages are:
```protobuf
// MembershipUpdateMessage is a message used to propagate information
// about group membership changes.
message MembershipUpdateMessage {
// The chat id of the private group chat
string chat_id = 1;
// A list of events for this group chat, first 65 bytes are the signature, then is a
Each membership update MUST be sent with a corresponding `chatId`.
The format of this chat ID MUST be a string of [UUID](https://tools.ietf.org/html/rfc4122 ), concatenated with the hex-encoded public key of the creator of the chat, joined by `-`. This chatId MUST be validated by all clients, and MUST be discarded if it does not follow these rules.
The signature for each event is calculated by encoding each `MembershipUpdateEvent` in its protobuf representation and prepending the bytes of the chatID, lastly the `Keccak256` of the bytes is signed using the private key by the author and added to the `events` field of MembershipUpdateMessage.
Upon receiving this event a client MUST validate the `chatId` provided with the updates and create a chat with identified by `chatId` and named `name`.
Upon receiving this event a client MUST validate the `chatId` provided with the updates and MUST ensure the author of the event is an admin of the chat, otherwise the event MUST be ignored.
Upon receiving this event a client MUST validate the `chatId` provided with the updates and MUST ensure the author of the event is an admin of the chat, otherwise the event MUST be ignored.
Upon receiving this event a client MUST validate the `chatId` provided with the updates.
If the event is valid a client MUST update the list of members of the chat who joined, adding the signer. Any `message` sent to the group chat should now include the newly joined member.
Upon receiving this event a client MUST validate the `chatId` provided with the updates, MUST ensure the author of the event is an admin of the chat and MUST ensure all `members` are already `members` of the chat, otherwise the event MUST be ignored.
Upon receiving this event a client MUST validate the `chatId` provided with the updates, MUST ensure that the author of the event is also the target of the event.
