The SALTO Virtual Network (SVN) provides the flexibility for an access control system to grow from a small number of doors and users to a large number of doors and users as required. It allows stand-alone locks to read, receive and write information via an encrypted and secure data-on-card system that utilizes the capabilities of RFID read/write technology. In SVN all access data is stored on and distributed by its operating smartcard. When presenting a smartcard to an offline stand-alone door, not only does this control access rights to that door but thanks to two-way communication, the door also writes data like blacklist information or battery status back to the smartcard. The smartcard then transmits this information back to the server via online wall readers that are able to update and receive information from the cards anytime and anywhere in the building.