MAC Aggregation over Lossy Channels in DTLS 1.3

Aggregating Message Authentication Codes (MACs) promises to save valuable bandwidth in resource-constrained environments. The idea is simple: Instead of appending an authentication tag to each message in a communication stream, the integrity protection of multiple messages is aggregated into a single tag. Recent studies postulate, e.g., based on simulations, that these benefits also spread to wireless, and thus lossy, scenarios despite each lost packet typically resulting in the loss of integrity protection information for multiple messages. In this paper, we investigate these claims in a real deployment. Therefore, we first design a MAC aggregation extension for the Datagram Transport Layer Security (DTLS) 1.3 protocol. Afterward, we extensively evaluate the performance of MAC aggregation on a complete communication protocol stack on embedded hardware. We find that MAC aggregation can indeed increase goodput by up to 50% and save up to 17% of energy expenditure for the transmission of short messages, even in lossy channels.