An Access Key also known as an Activation key was a small device about two to two and a half inches long, that contained a solid state memory core, and a small biometric reader. The Memory core contained all the users access codes, activation codes, personal information, log in data, and in some cases small bits of navigational data, it also contained records of up to 5 biometric profiles but usually just one.
The Biometric reader would take a sample of the individual using the device's bio-matter and compare it to samples on board the memory core. If a match, the Key would scan the slot it was in determine the appropriate information to send and do so. If there was no match, it would take a second sample and compare again, if still a failure the slot would retract, pulling the access key with it, and activate an alarm, while locking down the immediate area if possible.
Access keys could be used to gain access to secure rooms and areas, computers, ships, lock boxes, footlockers, even datapads. Use of them wasn't mandatory for most individuals of groups but higher ups used them because of the number of codes they had to remember and the added layer of security. Keys came in various shapes and forms and could even be customized.