QUIC-MLS:Making a Space Security Draft Standard Resilient for Disconnected Environments

Among standardization efforts for space and interplanetary network security, the Internet Engineering Task Force (IETF) is driving work on space network security, accounting for the unique properties of space environments that make space communication challenging. This includes long, variable-length delays, packet loss, and intermittent end-to-end connectivity. Within these efforts, there is a focus on using IP-based protocols for security, and in particular the use of the QUIC protocol. <br/><br/>This is unsurprising given QUIC's growing popularity and offer of optimization intended for reducing latency. However, QUIC uses the Transport Layer Security (TLS) key exchange handshake protocol, which was originally designed for "connect and forget" style Internet connections at scale. It is also session-based, where protocol participants require reestablishment of the session for each reconnection -- a costly maneuver in the space setting. Furthermore, TLS by default does not achieve strong post-compromise security properties within sessions, exhibiting a risk under long-lived connections, and need for synchronous handshakes to counteract this are in functional contrast to the space environment, which has intermittent end-to-end connectivity. <br/><br/>We address both drawbacks of QUIC by introducing QUIC-MLS: a variant of QUIC which replaces the session-based, synchronous TLS handshake with the standardized continuous key agreement protocol, Messaging Layer Security (MLS), which achieves asynchronous forward secrecy and post-compromise security. In addition to the design itself, we implement our design and provide benchmarks, and analyze our new construction in a formal cryptographic model.