隨著網際網路的應用不斷進步，各種藉由網際網路的電子商務行為、資訊傳播也蓬勃發展。然而，網路上的使用者在面對未知的或其不熟悉的物品時，傾向於先觀察其他人對於此物品的觀感，然後決定自己接下來採取的行動。信譽系統（Reputation system）正是一種利用推薦與評價，讓使用者藉由其他人對此物品的經驗中了解此物品之信譽評等的一種機制。
　　然而現今網路上普遍採用的信譽系統並非完美，容易受到sybil attack之攻擊，並且信譽系統所計算出之評價值未必對每個使用者都適用，因此本篇論文將提出一個更為安全以及參考價值更高的信譽系統。
　　本篇論文的信譽系統是針對物品（Product）或服務（service）來做出評價，並且與其他線上信譽系統不同之處在於，對於同一個物體，系統中每一個使用者所看到的評價都不相同，系統利用使用者給物體的評價來分辨出價值觀相近的人，再參考這些價值觀相近之使用者的評價來計算評價值。經由這種方式算出的來評價對使用者來說較有參考價值，惡意使用者想要成功發起sybil attack攻擊的難度也會大大提高。

　　The applications of internet are growing up day by day, many e-commercial behavior and information exchange become more. However, the users on internet tend to observe other people’s experience before making decide what to do when they meet the entities they don’t familiar. The reputation system is a mechanism which using rating and recommends and let users know some entity’s reputation from other people’s experience.
　　But the reputation system used on line is not perfect, it is easy to affect by Sybil attack and the reputation value the system provide is not suitable to every user. We propose a more secure and more accurate reputation system in this paper.
　　The reputation system we propose aim at products or services. The difference between other on-line reputation systems and our reputation system is that every entity’s reputation value is difference between every user in our reputation system. The system use the votes to distinguish the users have similar values, and use the users to compute reputation value. The reputation value computing from this method is more accurate and the success attack by Sybil attack is more difficult.

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