TeskaLabs SeaCat PKI is a key management system (KMS) and certificate management system (CMS) designed for mobile applications and IoT connected devices. The software facilitates secure electronic information transfer by managing digital certificates, keys, and identities throughout the device lifecycle from production to end of life. The system provides certificate issuance, automated renewals, and revocation capabilities. It supports X.509, C-ITS Security v1.3 and v1.2 (ETSI), and C-V2X Security cryptofamilies, along with RSA and EC asymmetric ciphers. The platform is compatible with Hardware Security Modules (HSM) through PKCS#11 interface for enhanced key protection. SeaCat PKI is deployed as a Docker-friendly microservice with REST API access. It supports multiple deployment options including on-premise, cloud, hybrid, physical/virtual appliances, and PKI as a Service. The system includes multi-tenancy support, allowing one PKI instance to serve multiple isolated projects. The platform has been implemented in C-ROADS pilot deployments in the Czech Republic and Slovenia for vehicle-to-everything (V2X) communication infrastructure. It provides device registration, lifecycle management, identity provisioning, and misbehavior detection capabilities for connected devices at scale.