| 摘要 |
<p>A computer system at a site determines 41 whether a network connection to a remote authentication source is available. If the connection is available, the system authenticates the user by interaction 42 with the remote source. The system authenticates the user against a user-provided credential if the connection is unavailable 43 or, in a preferred arrangement, in addition to remote authentication. The credential is preferably provided or validated by the remote source less than a predetermined time before authentication, e.g. 24 hours, and access to resources may be based on the credential. Preferably, the credential is a certificate issued by or on behalf of a trusted certification authority and may indicate a user role governing access to resources. The system may hold one or more certificates issued by the authority that relate to permissions for resources at the site. Access to specific resources may be permitted if allowed by both the credential and one or more of the systemâ s certificates. Preferably the site is a power generation facility, e.g. a wind park in which the system is either a SCADA (supervisory, control and data acquisition) server or is comprised within a wind turbine.</p> |
