Why Signal Still Leads in Secure Messaging Despite Human Errors

 By Nadim Kahwaji

The "Signalgate" scandal underscores the critical importance of secure communication protocols, especially among high-ranking officials. In March 2025, it was revealed that U.S. Defense Secretary Pete Hegseth and other senior Trump administration officials used the encrypted messaging app Signal to discuss sensitive military operations. Notably, a journalist was inadvertently added to a group chat where plans for a U.S. airstrike in Yemen were being discussed, leading to widespread concern over potential breaches of operational security.

Many people misunderstand the situation and wrongly assume that Signal's security is to blame, when in fact, Signal remains one of the most highly regarded messaging platforms for security and privacy. The actual incident involved the U.S. Defense Secretary accidentally adding an unauthorized individual, highlighting that even the most secure apps cannot compensate for user error.

Messaging apps such as WhatsApp, Signal, iMessage... use end-to-end encryption, meaning that only the communicating users can read the messages. The encryption keys are stored locally on the users’ devices, so even the app providers cannot decrypt or access the content of those messages.

For example, WhatsApp relies on its central server to manage group membership, meaning the server can add or remove members, and users’ apps will accept those changes without any cryptographic validation. This creates a potential risk, as the server could silently insert unauthorized members into a group. The situation becomes even more serious if someone gains control of the WhatsApp server, either through insider access or an external attack. In contrast, Signal handles group membership on the client side. Only the group creator or authorized admins can make changes, and these changes are digitally signed and verified by each member’s device. In Signal, the admin’s phone controls who is allowed in the group, and the app enforces these permissions cryptographically, preventing unauthorized modifications.

In Signal, each group has a Group Master Key that defines the group’s membership and security context. Each participant also generates a Sender Key, which is a symmetric key used to encrypt their messages to the group. When someone is added or removed from the group, including when a user leaves voluntarily, Signal automatically rotates the Group Master Key and re-establishes Sender Keys for all participants. This ensures that former members cannot decrypt any future messages, maintaining forward secrecy. All group changes must be digitally signed by an authorized admin and verified by every client, so the server has no power to alter group membership on its own.

In simpler terms, the Group Master Key is like the chat room key that grants access to the room, while the Sender Key is like the microphone key that lets you speak in the room. Apps like WhatsApp do not implement a Group Master Key, leaving group management less secure.

While Signal provides robust end-to-end encryption, ensuring message security during transmission, incidents like Signalgate and the French Minister's phone hack underscore that the app's security cannot compensate for user errors or device-level compromises.

If you’re looking for the most secure messaging platform, Signal remains the top choice. However, its security depends not just on the technology but also on how carefully you manage group membership. Even the most secure tools require responsible use to maintain privacy.