From Halopedia, the Halo wiki
Information cards are simple identification devices that are used to allow access to specific areas, prove someone's identity, or contain other pieces of information.
Known card types
ONI identification card
This card variant is used by ONI as identification. The cards usually feature an ONI insignia, a bar-code, and a code based on hexagons on it. Some also have a holographic image of the owner, and their CIN on it, with a chip at the back.
UNSC deck card
This card variant ensure the crew gets all-access to the deck of a specified ship.
Spartan optic calibration card