SoK: An Analysis of End-to-End Encryption and Authentication Ceremonies in Secure Messaging Systems

Instant-messaging (IM) and voice over IP (VoIP) applications like WhatsApp, Zoom, and Skype have made people extremely reliant on online communications for their audio, video, and text conversations. Since more people are using these platforms to talk to each other and share sensitive information, many ongoing concerns have been raised about how the government and law enforcement monitor these platforms. Due to these concerns, the need for a method to secure confidential messages and electronic conversations has grown. This solution could be achieved by implementing an end-toend encryption (E2EE) system without relying on any first or third parties, such as an online service or a centralized infrastructure like a public key infrastructure (PKI), which may be attacked, malicious, or coerced by law enforcement and government surveillance programs. In this systematization of knowledge paper, we first introduce the most popular E2EE apps, including their underlying E2EE messaging protocols. Then, based on the existing research literature, we investigate and systematize their E2EE features, including their underlying authentication ceremonies. Even though many research studies have examined some messaging services, we analyze and evaluate a broader set of the most popular E2EE apps and their underlying authentication ceremonies. Based on our evaluation, we have determined that all current E2EE apps, particularly when operating in opportunistic E2EE mode, are incapable of repelling active man-in-the-middle (MitM) attacks. In addition, we find that none of the current E2EE apps provide better and more usable authentication ceremonies, resulting in insecure E2EE communications against active MitM attacks. The conclusions of this systematization paper could influence future research in the field, including any improvements to the implementation of E2EE systems and authentication ceremonies that provide powerful protections against eavesdropping and MitM attacks.