SOAP: A Social Authentication Protocol

Authors: 

Felix Linker and David Basin, Department of Computer Science, ETH Zurich

Abstract: 

Social authentication has been suggested as a usable authentication ceremony to replace manual key authentication in messaging applications. Using social authentication, chat partners authenticate their peers using digital identities managed by identity providers. In this paper, we formally define social authentication, present a protocol called SOAP that largely automates social authentication, formally prove SOAP's security, and demonstrate SOAP's practicality in two prototypes. One prototype is web-based, and the other is implemented in the open-source Signal messaging application.

Using SOAP, users can significantly raise the bar for compromising their messaging accounts. In contrast to the default security provided by messaging applications such as Signal and WhatsApp, attackers must compromise both the messaging account and all identity provider-managed identities to attack a victim. In addition to its security and automation, SOAP is straightforward to adopt as it is built on top of the well-established OpenID Connect protocol.

Open Access Media

USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.