## 6 Identity Management in FRMCS Security and Safety  
In [11], the required features and functions of an FRMCS system are defined. The main attributes of a secure FRMCS system include data integrity, data confidentiality, information privacy, the non-repudiation of data origin, and availability. Three independent security layers for FRMCS system are defined:  
* In the railway application stratum, the security mechanisms are application-specific and are independent of the FRMCS.
* In the service stratum, the security mechanisms exist between FRMCS service clients and the FRMCS server, and include authentication, data integrity, data confidentiality, and data privacy.
* In the transport stratum, the security mechanisms are independent of the railway application stratum and service stratum.  
The proposed services can be used to implement the required functionality of the security mechanisms in the service stratum.  
In the service stratum, integrity can protect all types of data (e.g., user data and positioning information), and identity management may be used as a key integrity function. The confidentiality in the service stratum also aims to protect all types of data, and identity management may be used as a key function during the encryption process. The privacy in the service stratum protects the integrity and confidentiality of the equipment and user identities and may be implemented using one-time identities with limited validity. In the service stratum, non-repudiation allows the origin of data to be determined and includes functions for access protection, internal security, and interface security. Identity management and role management may be used during access protection for identification, authentication, and authorization. Internal security functions and the security functions of interfaces from/to external systems are implementation dependent.  
The specifics of the security mechanism are not defined in the FRMCS standard and should be studied in future work.  
The security of the communications between FRMCS service clients and FRMCS servers is an issue related to the transport stratum and may rely on the proven Internet Protocol Security (IPSec) architecture, Hypertext Transfer Protocol Secure (HTTPS) for RESTful services, and the elaborated security mechanisms of fifth-generation mobile networks.  
Safety is a key requirement for railway operation because if it is not managed properly, then passengers, on-board and trackside staff, and infrastructure damages may occur. FRMCS standards define use cases for on-train safety devices to ground communications [10]. The use cases include:  
* The initiation of on-board safety device data communication,
* The termination of on-board safety device data communication,
* Voice communication between the driver and controller.  
These use cases utilize the identity management functionality. According to [10], a driver safety device is an on-board system that monitors driver alertness and issues warnings and alarms to other systems as appropriate. Pre-conditions assume that the identities of the user and equipment are registered and authorized to initiate ground data communication in the safety devices. Voice and/or data communication is automatically setup in case of emergency, e.g., by a driver safety device using an assured data communication service. Train information such as the functional identity is sent to the ground user. The functional identity provided by role management and presence applications as well as other information is used by the FRMCS system to determine the responsible controllers and the ground system in question. During the communication, the information gained from the role management and presence applications is used to present the identity of the on-train device to the controller.