A mobile device including a communications interface, a memory, a display screen, and a processing unit. The processing unit is configured to retrieve a first key of an asymmetric key pair. A second key of the asymmetric key pair is stored on an access control device. The processing unit is configured to generate a plurality of barcodes. Each of the barcodes includes data that is encrypted using the first key and the current date and time. At least some of the barcodes are distinct from one another. At least one of the barcodes includes access information. The processing unit is configured to sequentially display the barcodes such that only a single one of the barcodes is displayed on the display screen of the mobile device at a single time. The barcodes are read and decrypted by the access control device using the second key and the current date and time.