Key management requirements for Positive Train Control communications security

Positive Train Control (PTC) is an electronic system that enforces train separation, speed enforcement, roadway worker protection and a host of other activities essential to operate railroads safety and efficiently that requires wireless communication to exchange control and sensory information between mobile locomotive and static control centers and wayside devices. This requires communication security ensuring the freshness, confidentiality, integrity, and authenticity of the information. For that purpose, we propose a cryptography based key management system (KMS). This paper outlines the requirements for a KMS, provides a proposed key distribution method, and highlights several significant implementation tradeoffs