A user key validation during a handoff verifies the subscriber using the wireless communication system and prevents fraudulent use of the system. A wireless communication system (10) has a number of satellites (20, 22, 24) with which a subscriber unit (12) establishes a communication link. However, as the quality of the transmitted signal between an active satellite (22) and the subscriber unit (12) degrades, a handoff of the communication link with the subscriber unit (12) will occur if the subscriber (12) meets the authentication requirements of the system (10). The active satellite (22) generates user keys and transmits the user keys to the active subscriber units (12). A request of a handoff is made from the individual subscriber unit (ISU) (12) to the losing SV (22). The losing SV (22) communicates with the gaining SV (20) to establish a handoff. The losing SV (22) sends the user key of the ISU (12) to the gaining SV (20). The gaining SV (20) authenticates the ISU (12) by comparing the ISU user key to a user key stored in the losing SV (22). The gaining SV (20) becomes the active satellite, and generates and transmits the user key to the ISU. Notification of the authentication is sent to an earth terminal controller (30). The earth terminal controller (30) provides the losing SV (22) with notification that the handoff is complete. The authentication a prevents further fraud if the subscriber fraudulently obtained access to the system during the original call set up.