SURA: Secure Unsourced Random Access

This work introduces security for unsourced random access (URA) by employing physical layer security techniques. To achieve confidentiality, the proposed system opportunistically exploits intrinsic features of feedback-aided URA without adding any overhead or altering its original structure or operational characteristics. As a result, the proposed system preserves the low-cost advantages of URA, including low delay and minimal signaling overhead, while providing secure communication. To secure transmission, each user generates a secret key from a feedback signal broadcast by the BS in a previous transmission round. This feedback depends on the BS-user channel, making it a private signal for each user. Secure transmission is achieved not only through encryption using the secret key, but also by transmitting only the parity bits of the LDPC-encoded key, thereby enabling its recovery at the legitimate receiver via Slepian-Wolf decoding with side information. For reception, a receiver algorithm is designed for the legitimate receiver, and a leakage analysis is provided to quantify the information available to the eavesdropper. The simulation results show that meaningful secrecy is achieved in URA without modifying its structure.