About credit card size Not readable with magnetics Randomized internal key(s) Durable long-term storage for keys (decades? centuries?) Inside reader log storing reader device id and time stamps (from system?) Protected and tamper safe System can compare with system logs upon reading (to detect unauthorized use/copying) System can detect and warn for device having been accessed by unknown readers/copiers System can detect and warn for readings outside of working hours System can detect and warn for excessive number of readings in a day (e.g. one more than normal) Can be produced with slider to protect connectors Slider can be opened by reader