This research proposes a lightweight tamper resistant client file in an external memory as an alternative to smart card for remote user authentication and access control. The benefit of using this special client file is portability and ease of acquirement, especially in school online portals, online resources portals, and e-commerce portals. The characteristics and design considerations that make smart card tamper resistant are reviewed. Techniques and characteristics to make a client file in an external memory to exhibit a lightweight tamper resistant property has been formulated. The Kumari et al.'s scheme, which is the latest research that uses external memory for remote user authentication, has been reviewed. The basic system design and software design of the proposed client file is presented and modeled. This will enable implementation of the proposed system using any prepared programming or scripting language of one's choice. The proposed scheme and reviewed scheme are also evaluated for efficiency, tamper resistance, and impersonation attack.