SURA: Secure Unsourced Random Access

This work introduces security for unsourced random access (URA) by employing wiretap-inspired physical layer 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 and an artificial noise sequence from the feedback signal that the BS broadcasts in previous transmission rounds. This feedback depends on the BS-user channel, making it a private signal for each user. The secure transmission is performed by three actions: encrypting the data using the secret key, sending only the parity bits of the LDPC encoded secret key to allow the legitimate receiver to recover it, and masking these parity bits with the artificial noise. For reception, a receiver algorithm is designed for the legitimate user, 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 and with negligible impact on standard performance.