Paper 2025/1701 Original: eprint.iacr.org/2025/1701 ↗

BPSec-MLS: Asynchronous Key Agreement for Space Communications

Abstract

Key agreement is the cornerstone of any secure communications channel whether over the traditional internet or in delay tolerant networks used in space communications. However, space systems that rely on pre-shared keys face insurmountable limitations in both security and scalability. A single key compromise can expose all past and future encrypted communications, and the static nature of pre-shared keys prevents dynamic group membership, making it difficult to add or remove devices without invalidating entire key sets. To address these challenges, the Messaging Layer Security (MLS) protocol -- a recently introduced internet standard for asynchronous group key establishment -- offers promising capabilities. Its potential to provide efficient and dynamic key agreement for federated interplanetary architectures (e.g. government-commercial collaborations) has been previously recognized, particularly with integration of MLS with the Bundle Protocol Security (BPSec) framework. In this work, we present the first empirical findings on the integration of MLS with BPSec in a realistic space communications scenario and provide insights into its deployment in future space architectures.