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.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (46 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the SLPKMF (Sidelink Positioning Key Management Function) was newly introduced as an optional network function for which address information can be provisioned to a UE as part of the Ranging and Sidelink Positioning Policy (RSLPP). This policy is delivered via the UE policy delivery service, allowing the UE to be configured with the necessary SLPKMF contact details to support security procedures for sidelink positioning.
- Nudm_SDM retrieval of SMS Management Subscription data TS 29.503CR0037
In Release 17, the SLPKMF (Sidelink Positioning Key Management Function) saw its address information formally defined as an optional configuration parameter within the Ranging and Sidelink Positioning Policy (RSLPP). This was part of broader enhancements to provisioning, which also extended support for both 5G ProSe and V2X service mapping rules within the policy. These updates were integrated alongside the introduction of procedures for dynamic UE policy delivery and the expansion of ProSe subscription data management.
- Add 5G DDNMF and ProSe Subscription Data TS 29.503CR0613
- Shared Session Management Subscription Data TS 29.503CR0678
- Dynamic management of group based event monitoring TS 29.503CR0702
- Extends Multiple Data Sets for ProSe Subscription Data TS 29.503CR0707
- ProSe Subscription Data TS 29.503CR0708
- Resolve EN for 5G ProSe Services Operations TS 29.503CR0917
In Release 18, the SLPKMF function was updated to support new privacy and subscription management features for sidelink positioning. Specifically, the release introduced a dedicated sidelink positioning privacy check procedure and defined new subscription data types for Ranging Sidelink Positioning and UE RangingSL Positioning privacy profiles. These enhancements were detailed in a general update to the specification for SLPKMF services.
- Sidelink positioning privacy check procedure TS 24.514CR0001
- Session Management Subscription data for HR SBO in VPLMN TS 29.503CR0985
- Ranging Sidelink Positioning Subscription data TS 29.503CR1094
- Additional Shared DNN Config IDs in Session Management Subscription Data TS 29.503CR1107
- Support on Indication of user plane positioning between UE and LMF TS 29.503CR1135
- Support the 5G ProSe End UE TS 29.503CR1163
+ 25 more changes
In Release 19, the SLPKMF function was updated with clarifications and corrections to existing procedures, including the sidelink positioning service request for the located UE and the description for SL positioning server UE selection. The updates also addressed the UEID reference and editorial errors for SLPKMF services, and provided a clarification on the required QoS for positioning the located UE(s).
- Local Offloading Management TS 29.503CR1379
- Corrections on located UE in sidelink positioning service request procedure TS 24.514CR0035
- Clarification on description of sidelink positioning SLPP transport initiation TS 24.514CR0036
- Correction to T5aaa and ProSe clock reference TS 24.514CR0038
- Clarification on required QoS for located UE(s) positioning TS 24.514CR0058
- Clarification on roles in RSPP metadata of the PROSE PC5 DISCOVERY message TS 24.514CR0061
+ 2 more changes
Explore further
Broader topics and technologies where SLPKMF plays a role.
Defining Specifications
3GPP specifications that define or reference SLPKMF, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 24.514 vj30 | Ranging & Sidelink Positioning in 5GS | Rel-19 |
| TS 29.503 vj50 | UDM Service Based Interface Stage 3 | Rel-19 |
| TS 29.586 vj30 | SLPKMF Service Based Interface Protocol | Rel-19 |
| TS 33.533 vj00 | Security for 5G Ranging & Sidelink Positioning | Rel-19 |