Abstract: An anti-passback algorithm for an access control system is described. The anti-passback algorithm prevents the use of valid credentials to gain access to an access-controlled area by more than one person within a given period of time. The algorithm is capable of distinguishing between credentials intentionally presented to the access control system and credentials that are unintentionally read by the access control system. Certain variables may be set by the access control system manufacturer or a trusted individual to adapt the algorithm for applications.

Abstract: Readers are associated with a number of access credentials and, once authenticated by the reader, may grant the holder of the access credential access to a secured asset. Readers may become the target of attack, such as when an unauthorized party attempts to gain access to the interior of the reader or removes the reader from an installed location. Once removed the reader may be reinstalled in another location or a counterfeit reader used in its place. By providing a paired tamper credential, the reader may deny otherwise authorized access to the secured asset if the tamper credential fails to respond appropriately. The tamper credential may fail to respond due to distance, such as when the reader alone is relocated, or the tamper credential is damaged, such as during an attempt to gain access the interior of the reader and/or remove the reader from its installed location.

Abstract: An anti-passback algorithm for an access control system is described. The anti-passback algorithm prevents the use of valid credentials to gain access to an access-controlled area by more than one person within a given period of time. The algorithm is capable of distinguishing between credentials intentionally presented to the access control system and credentials that are unintentionally read by the access control system. Certain variables may be set by the access control system manufacturer or a trusted individual to adapt the algorithm for applications.