Objectives: Authentication is the first step of secure communication. Especially, cloud environment is a critical issue for user authentication because cloud storages have a lot of user credentials. Methods/Statistical Analysis: To solve this problem, security USB is released currently, especially in the public sector, use a mandatory system of security USB memory in the enterprise has been applied. However, information for user authentication or be stored in plain text in a specific area of the USB memory, vulnerabilities that can be authenticated bypassed by user interaction is found. Findings: Cloud storage services are getting popular and it must be secured. Otherwise, personal privacy could be compromised. Once username and password are compromised, valuable information will be in jeopardy. USB memory is small, cheap and the capacity ratio of price as a portable storage medium to provide a large capacity, it has secured already many users. Further, due to the small size, often lost or stolen accident, flows out the data in the USB memory, social problems such as major technology leakage of effluent and industrial personal information has occurred. Improvements/ Applications: To solve the vulnerability of such user’s authentication, by using the structure properties of the hash function and encryption algorithm and the storage medium presents a secure user’s authentication methods.