SideLink Positioning Key Management Function

Description

The Sidelink Positioning Key Management Function (SLPKMF) is a security function defined in 3GPP Release 18 as part of the enhanced architecture for Sidelink positioning and Proximity Services (ProSe). It operates within the security framework for direct device-to-device (D2D) communication, known as the Sidelink (SL), which is crucial for V2X, public safety, and commercial ProSe applications. The primary role of the SLPKMF is to manage the lifecycle of cryptographic keys specifically used for securing positioning procedures conducted over the Sidelink. This includes the generation, storage, distribution, and revocation of keys such as the Sidelink Positioning Key (SLPK). When User Equipments (UEs) need to perform secure relative positioning (e.g., for collision avoidance in V2X), they require authenticated and integrity-protected positioning measurement messages. The SLPKMF, typically residing in the home network, provisions the necessary keys to authorized UEs via secure signaling with other network functions like the Authentication Server Function (AUSF) and the ProSe Function. The UE uses these keys to derive session keys for protecting Sidelink Positioning Protocol (SLPP) messages or related positioning reference signals. The function ensures that only authorized devices can participate in secure positioning exchanges, preventing spoofing, replay attacks, and eavesdropping on sensitive location data. Its operation is closely tied to the overall ProSe security architecture, interacting with the ProSe Key Management Function (KMF) and leveraging the 5G core network's security mechanisms.

Purpose & Motivation

The SLPKMF was created to address the specific security requirements for positioning over the Sidelink, a capability that became critical with the advancement of V2X and advanced ProSe services in 5G NR. Earlier releases of ProSe and V2X focused on basic communication security but lacked a standardized, dedicated mechanism for securing positioning-related signaling and measurements exchanged directly between devices. As applications like autonomous driving and high-accuracy relative positioning emerged, the need for secure, trustworthy location information became paramount to prevent safety-critical threats such as location spoofing in collision avoidance systems. The SLPKMF solves this by providing a standardized, network-assisted key management framework tailored for Sidelink positioning. It addresses the limitations of ad-hoc or application-layer security by integrating into the 3GPP network's trust model, allowing for centralized policy control, key lifecycle management, and support for roaming scenarios. Its introduction in Release 18 was motivated by the need to enable secure, high-accuracy positioning services for V2X, industrial IoT, and public safety, where the integrity of location data is as important as the communication itself.