考慮路由器的廣播加密機制

Abstract

廣播加密機制(broadcast encryption)是一種讓管理中心可以有效的廣播數位內容給廣大使用者的加密機制，使得只有非註銷使用者才有能力解開內容。廣播加密機制有廣泛的應用，例如在網際網路或行動無線網路上廣播電影、新聞、以及付費電視。 廣播加密機制分成有狀態型(stateful)與無狀態型(stateless)，無狀態型的機制雖然需要較長的廣播訊息複雜度(message complexity)，卻可以避免使用者必須參與全部金鑰更新過程這樣的條件。在無狀態型廣播加密機制中，目前最為可行的是子集差別方法(subset difference)。 在本篇演算法中，我們研究子集差別方法，發覺此方法所找出的覆蓋集合中，有些覆蓋是較無效率的。而實際的廣播加密應用上，並不是所有的非法使用者都一定要馬上被註銷其權限。我們提出新的方法，使得訊息複雜度比SD少了約1/3，並且在適當路由器配合下，我們的方法也可以達到完美的註銷，使得所有非法使用者都無法解開訊息。

Broadcast encryption scheme is a method let manager center broadcast digital content to large number of users efficiently and guarantees that only legal users have the ability to get the content. Broadcast encryption schemes have vast applications such as broadcasting movies, news on networks, and paid TV. There are stateful and stateless broadcast encryption schemes. Although stateless schemes need more message complexity, they don’t need users to keep online all the time. Among all of the stateless broadcast encryption schemes, subset difference method is the most practical. In this paper, we researched subset difference method, and found some inefficient covers. In the practical applications, we don’t need to revoke all illegal users immediately. Thus, we propose a new method that reduces its message complexity to 2/3 of SD’s. Our method can have the perfect revocation in the help of special routers.