A mobile device receives a shared access key corresponding to a work machine. An access code is generated from the shared access key, and from a changing value (such as a time-sensitive value). The access code is transmitted to the work machine which, itself, calculates an access code based on the shared access key and based on the changing value. If the access code provided to the work machine and the access code generated by the work machine match one another, then the work machine unlocks corresponding functionality so that the operator can use the work machine.