A counter synchronization process is described that is event driven rather than conducted on a periodic basis. A receiving device, which may be a user equipment (UE) or a base station, monitors received data packets to detect a rollover of a packet data sequence number in successive data packets. When the sequence number rollover is detected, the receiving device increments the variable data portion of the deciphering key stored in memory. Also in response to this detected rollover event, the receiving device transmits a synchronization message to the source device.