Security feature: signature status when participating in a chat
As of version 4.35, information about the status of the encryption signature is displayed in the info of the respective end-to-end encrypted chat. This information is displayed to the user equally in all clients (web and desktop client, iOS and Android).
The status of the signature is an additional security information and should inform the user about a possible attack on the end-to-end encryption of the chat. The signature is created with the private key of the creator or the inviter of the corresponding chat. The participating user verifies the signature and displays the result in the app. Complex man-in-the-middle attacks on the end-to-end encryption are supposed to become visible via this.
3 different statuses can occur:
- Signature valid (green): The signature is present and valid. The chat access key was sent by the inviting user and has a valid private key signature.
- Signature not present (yellow): The chat access key was sent without a signature. This can happen if the inviting user is using an app version without signature support. For chats created before version 4.35, this is always the case and does not represent an attack on the chat content.
- Invalid signature (red): The chat access key was sent with a signature that does not match the inviting user’s current private key. This can happen if the user’s private key has changed, e.g. by resetting the encryption password after the chat access was sent. To make sure that the access was actually initiated by a real user, it is a good idea to check with the person outside the app.
In upcoming versions, this feature will be complemented by another security feature for manual validation of users.