Encrypting Underwater Acoustic Communications: Low-Bandwidth and Cross-Layer Challenges

The operational use of underwater acoustic communications, particularly in a military context, requires adequate security measures. The minimum level of security required is protection of the user payload in the message, so this is the way to start. Main challenge is the inherently low bandwidth of underwater acoustic communications, which provides limitations for encryption overhead in the message and, especially, for in-situ underwater key management. The present study demonstrates how end-to-end security can efficiently be achieved in practice by securing the application layer of (crewed) source and destination nodes using open-source libraries for symmetric encryption, a common secret key and some overhead to guarantee uniqueness of the encrypted payload. Additionally, the paper outlines future challenges, such as protection of the network and physical layers, key management and message authentication.