ISO 21177:2023

Overview

ISO 21177:2023 - Intelligent transport systems - ITS station security services for secure session establishment and authentication between trusted devices - specifies a set of security services for ITS stations to ensure authenticity and integrity of information exchanged between trusted entities. The standard covers secure session establishment and authentication between bounded secured managed entities (ITS Station Communication Units - ITS‑SCU) and ITS station units (ITS‑SU), as well as between ITS‑SUs and external trusted entities such as sensor and control networks.

Key topics and technical requirements

• Secure session establishment and authentication: Services and procedures to negotiate trusted sessions that protect source authenticity and message integrity. The standard clarifies how these services relate to Transport Layer Security (TLS) and to application-level specifications.
• Architecture and functional entities: Definitions of roles and components (ITS‑SCU, ITS‑SU), cryptomaterial handles, session identifiers and session state management.
• Access control and authorization state: Mechanisms and PDUs for access control (e.g., AccessControlPdu, AccessControlResult) and how access policy is enforced during sessions.
• Authentication enhancements: Support for enhanced and extended authentication workflows, including a referenced method using SPAKE2 for password-authenticated key exchange.
• Service primitives and interfaces: Application–security (App‑Sec) interface primitives such as App‑Sec‑Configure, App‑Sec‑StartSession, App‑Sec‑Data, App‑Sec‑EndSession and related confirm/indication primitives to integrate security services with ITS applications.
• Process flows and sequence diagrams: Detailed flows for Configure, Start session, Send/Receive data, Extend session, Secure connection brokering and session termination.
• Security management information: PDUs and messages for certificate/CRL requests and security management information exchange.

Applications and who uses this standard

ISO 21177:2023 is essential for implementers and stakeholders building secure ITS ecosystems:

• Vehicle OEMs and automotive cybersecurity teams implementing secure V2X/ITS stations
• Roadside infrastructure and traffic management operators deploying trusted roadside units
• Suppliers of ITS‑SCU and ITS‑SU hardware/software modules
• System integrators and security architects designing time‑critical safety systems and automated driving features
• Remote management and maintenance platforms for ITS stations (linked to ISO 24102‑2)

Practical applications include time‑critical safety messaging, automated driving communications, roadside/infrastructure services, and secure remote management of ITS devices.

Related standards

• ISO 21217 - ITS station and communication unit definitions (ITS‑SCU, ITS‑SU)
• ISO 24102‑2 - Remote management of ITS stations
• Transport Layer Security (TLS) - referenced for relationship to session security

Keywords: ISO 21177:2023, ITS station security services, secure session establishment, authentication between trusted devices, ITS‑SCU, ITS‑SU, ITS security, automated driving security, access control PDU, SPAKE2, cryptomaterial handles.