Abstract: A mobile OTP system providing system is provided, in that it performs security token and OTP management functions, it generates an OTP having high security level in hardware by using a mobile OTP device for performing a security data storage function of encoding and decoding data during data storage, and it generates OTPs necessary for a plurality of services by using one mobile OTP device, thereby safely and easily utilizing it by means of the user.

Abstract: Provided are a security key device for a cloud service, and a system and a method for providing a secure cloud service. The security key device includes: an interface unit detachably connected to a user terminal, and providing an interface with the user terminal; a storage unit storing an encoded user file; and an encoding/decoding transformation supporting controller that, when receiving from the user terminal a file to upload to a cloud server, encodes the file, stores the encoded file in the storage unit, and then transmits the encoded file to the user terminal, and when receiving from the user terminal an encoded file downloaded from the cloud server, stores the encoded file in the storage unit, decodes the encoded file, and transmits the decoded file to the user terminal.