SP²-RD2D: Secure and Privacy-Preserving Authentication and Key Agreement Protocol for D2D Relay Communication

As a new paradigm among various D2D communication applications and use cases, D2D relay communication is a powerful underlay for 5G/6G to extend network coverage and increase communication reliability at the edge of cells. Despite its benefits, new application scenarios and system architecture expose D2D relay communications to unique security and privacy threats. Existing works proposed by neither 3GPP specifications nor academic research literature adequately address the issues of system security, privacy, and efficiency. To fill this gap, we propose SP<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RD2D, a lightweight secure and privacy-preserving authentication and key agreement protocol in D2D relay communication. This protocol enables remote users located outside or at the edge of the cell to establish a secure connection to the service network through relays. Meanwhile, SP<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RD2D provides identity privacy preservation for remote users and relays. We analyze the security of SP<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RD2D and assess its performance from both theoretical analysis and experimental evaluations. The result indicates that the proposed protocol effectively meets security and privacy requirements, demonstrating high efficiency in both computational and communication aspects.