Group accesses with smart card and threshold scheme

We describe the design of an access control mechanism that permits access to an empty laboratory only to groups of authorized students of a size satisfying a prescribed threshold. The scheme employs a shared-secret scheme, symmetric cryptography together with smart card technology. The access right of a student is carefully encoded and stored on a smart card. Access records are kept on these smart cards in a distributive fashion and with duplication. Students are able to present verifiable information regarding their recent accesses to the laboratory. The scheme eliminates the need for expensive wiring to a remote central database of authorized users and hence permits the use of a standalone controller