隨著電子商務[1]快速成長，電子商務(如線上銀行、購物、交易)最常要求使用者輸入帳號(Username)與密碼(Password)來登入系統，進行身分驗證。由於每位使用者可能同時使用多個電子商務系統，所以，要記憶多組帳號與密碼極有可能造成他們的困擾。另外，在這開放的網路世界，合法使用者的帳號與密碼遭有心人士盜取使用的新聞時有所聞。再則，近年來電子商務系統常使用透過簡訊來傳送一次性動態密碼[2] OTP (One Time Password)，來保護使用者的身分驗證。使用者收到簡訊後，再次輸入其OTP，才能登入系統。
基於許多電子商務使用者習慣攜帶其行動裝置，本論文主要討論使用者登入電子商務時，在其行動裝置安裝OTP產生器的方便與優點，並從OTP產生器取得OTP，且這組OTP只能使用一次。通過使用OTP登錄到不同的電子商務系統，使用者可免於混淆他們的使用者帳號和密碼，來確保他們登錄系統的安全性。

With the fast growth of e-commerce [1] systems, more and more people rely on them to finish their tasks, such as using an online banking, shopping, or trading. The users of the systems are usually required to type in their username and password to log into the system to verify their identity. However, these users may find it difficult to memorize all of the usernames and passwords for different systems if a number of systems are used. In addition, it is often heard that a user’s username and password for a system are phished in cyberspace. Therefore, in order to protect users’ authentication, e-commerce systems now more frequently send a one time password (OTP) through a text to their users. The users can use their OTP they receive to log onto the e-commerce system.
Many e-commerce users are used to carrying a mobile device with them. The thesis will mainly discuss the convenience and advantages of using a mobile device to log into a system with an OTP. Users use an OTP generator in their mobile device to gain an OTP. This OTP can be used just once. By using the OTP to log onto an e-commerce system, users may not confuse their usernames and passwords for different websites as well as ensure their safety when logging into systems.

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