Public key infrastructure (PKI) certificates are certificates with visibility external to organizational systems and certificates related to the internal operations of systems, such as application-specific time services. In cryptographic systems with a hierarchical structure, a trust anchor is an authoritative source (i.e., a certificate authority) for which trust is assumed and not derived. A root certificate for a PKI system is an example of a trust anchor. A trust store or certificate store maintains a list of trusted root certificates.