Final answer:
The cryptographic contactless technique used by the employee to access a building is RFID technology.
Step-by-step explanation:
The cryptographic contactless technique that allows an employee to access a building is known as RFID (Radio Frequency Identification) technology. It uses electromagnetic fields to automatically identify and track tags attached to objects, including access cards or key fobs. These tags contain unique identification information that is read by a reader device to grant or deny access to the building. The contactless nature of this technique means that the employee doesn't have to physically insert the card into a reader, but can simply hold it near the reader for authentication.