A registration system includes a management apparatus configured to acquire first information of an authentication key for registration from a communication processing apparatus to communicate with the management apparatus, put a signature for the first information with a first registration key, and transmit the first information completed with the signature to the communication processing apparatus, and a registration server configured to acquire a registration request including the first information completed with the signature by the management apparatus from the communication processing apparatus to communicate with the registration server, verify the signature put for the first information included in the registration request, by using a second registration key paired with the first registration key, and register the first information included in the registration request, based on a result of verifying the signature put for the first information.