A relay server comprising: a storage configured to store first access right information for a first user subscribed to a first cloud storage service and second access right information for a second user subscribed to a second cloud storage service; a communication interface configured to: request, from the first cloud storage service, first data that is stored in the first cloud storage service, based on the first access right information in response to a share request from the first user; and receive the requested first data from the first cloud storage service; and a controller configured to control the communication interface to store the received first data in a user space of the second user in the second cloud storage service, based on the second access right information; wherein the communication interface is arranged to send a request to the second user to grant the relay server the second access right information to store the first data in storage space of the second user in the second cloud storage service, and wherein the communication interface is further configured to receive, from a device of the first user, a read protection request for a portion of a file among the first data, and wherein the controller is further configured to: acquire the file from the first cloud storage service in response to the communication interface receiving the read protection request; apply read-protection to the portion of the file; and store the read-protected file in the second cloud storage service. a storage configured to store first access right information for a first user subscribed to a first cloud storage service and second access right information for a second user subscribed to a second cloud storage service; a communication interface configured to: request, from the first cloud storage service, first data that is stored in the first cloud storage service, based on the first access right information in response to a share request from the first user; and receive the requested first data from the first cloud storage service; and a controller configured to control the communication interface to store the received first data in a user space of the second user in the second cloud storage service, based on the second access right information; wherein the communication interface is arranged to send a request to the second user to grant the relay server the second access right information to store the first data in storage space of the second user in the second cloud storage service, and wherein the communication interface is further configured to receive, from a device of the first user, a read protection request for a portion of a file among the first data, and wherein the controller is further configured to: acquire the file from the first cloud storage service in response to the communication interface receiving the read protection request; apply read-protection to the portion of the file; and store the read-protected file in the second cloud storage service. request, from the first cloud storage service, first data that is stored in the first cloud storage service, based on the first access right information in response to a share request from the first user; and receive the requested first data from the first cloud storage service; and a controller configured to control the communication interface to store the received first data in a user space of the second user in the second cloud storage service, based on the second access right information; wherein the communication interface is arranged to send a request to the second user to grant the relay server the second access right information to store the first data in storage space of the second user in the second cloud storage service, and wherein the communication interface is further configured to receive, from a device of the first user, a read protection request for a portion of a file among the first data, and wherein the controller is further configured to: acquire the file from the first cloud storage service in response to the communication interface receiving the read protection request; apply read-protection to the portion of the file; and store the read-protected file in the second cloud storage service. acquire the file from the first cloud storage service in response to the communication interface receiving the read protection request; apply read-protection to the portion of the file; and store the read-protected file in the second cloud storage service.