Seyed Mohammad Kashani (Dept. of Electrical and Computer Engineering, Iowa State University), Branden Buhler (Dept. of Electrical and Computer Engineering, Iowa State University), Sang Wu Kim (Dept. of Electrical and Computer Engineering, Iowa State University), Ashfaq Khokhar (Dept. of Electrical and Computer Engineering, Iowa State University)
Relay-assisted satellite networks rely on multi-hop architectures that expose data integrity to malicious or compromised relays. End-to-end Message Authentication Codes (MACs) avoid trusting relays but delay error detection until the destination, incurring costly retransmissions over long-delay space links, while hop-by-hop integrity requires trusting intermediate nodes. We propose a superposition-coded integrity scheme in which the source embeds the end-to-end MAC tag directly into the physical-layer waveform, allowing the destination to recover the tag independently of relay behavior. This prevents tag forgery even when a relay possesses the end-to-end key and eliminates the need to forward authentication data through relays. We validate the approach using a three-node software-defined radio testbed and show improved authentication reliability under malicious relay scenarios.