A license management device configured to manage at least one communication-related function for a wireless licensee device, the license management device comprising: a request receiving unit configured to receive a license change request from the licensee device requesting to unlock or restrict at least one communication-related function; a default applying unit configured to, upon the request receiving unit receiving the license change request, overwrite stored key information of the licensee device with a default key which is specific to the licensee device, the default key representing an initial setting of the key information restricting the at least one communication-related function; an upgrade key requesting unit configured to transmit an upgrade key generation request including identification information of the licensee device and at least one communication-related function to be unlocked that are represented by the received license change request, to a key generating device that generates an upgrade key that is difference data between: i) key information unlocking the at least one communication-related function restricted by the default key of the licensee device; and ii) the default key based on the identification information of the licensee device and that is encrypted using an encryption key that is associated with the licensee device; an upgrade key acquiring unit configured to acquire, from the key generating device, the encrypted upgrade key generated in response to the upgrade key generation request transmitted by the upgrade key requesting unit; and an upgrade applying unit configured to apply the encrypted upgrade key to the key information of the licensee device after the default applying unit has overwritten the key information with the default key. a request receiving unit configured to receive a license change request from the licensee device requesting to unlock or restrict at least one communication-related function; a default applying unit configured to, upon the request receiving unit receiving the license change request, overwrite stored key information of the licensee device with a default key which is specific to the licensee device, the default key representing an initial setting of the key information restricting the at least one communication-related function; an upgrade key requesting unit configured to transmit an upgrade key generation request including identification information of the licensee device and at least one communication-related function to be unlocked that are represented by the received license change request, to a key generating device that generates an upgrade key that is difference data between: i) key information unlocking the at least one communication-related function restricted by the default key of the licensee device; and ii) the default key based on the identification information of the licensee device and that is encrypted using an encryption key that is associated with the licensee device; an upgrade key acquiring unit configured to acquire, from the key generating device, the encrypted upgrade key generated in response to the upgrade key generation request transmitted by the upgrade key requesting unit; and an upgrade applying unit configured to apply the encrypted upgrade key to the key information of the licensee device after the default applying unit has overwritten the key information with the default key.