Transmission of authentication keys

A computer includes a processor and a memory storing instructions executable by the processor to, upon receiving an authorization message, transmit a plurality of new authentication keys to a respective plurality of control modules, the memory including an expiration time for the authorization message; update a listing of the control modules with respective statuses of the transmissions of the respective new authentication keys to the respective control modules, wherein each status is one of successful or unsuccessful; upon at least one status being unsuccessful, prevent the authorization message from expiring at the expiration time; after preventing the authorization message from expiring, retransmit the respective new authentication keys to each control module for which the respective status is unsuccessful; and then expire the authorization message.