In one example, a first wireless device transmits one or more electronic keys, and a second wireless device receives and stores the electronic key(s) in a memory. A server or a user device uploads, receives or synchronizes the electronic key(s) from the second wireless device. In another example, one or more electronic keys are transmitted using a first wireless device, the electronic key(s) are received and stored in a memory of a second wireless device, and the electronic key(s) or other data are transmitted, uploaded or synchronized to a server or a user device. In another example, a device comprises: a wireless transceiver; a memory; and a processor communicably coupled to the wireless transceiver and the memory, wherein the processor receives one or more electronic keys from one or more wireless devices, and stores the electronic key(s) in the memory.