多授權中心的屬性加密及其實現

Abstract

屬性加密系統提供了細粒度的存取控制，這是傳統的公開金鑰加密系統，如RSA或ElGamal所做不到的。在屬性加密系統裡，加密者可以決定一個存取公式，這個存取公式控制了哪些私鑰可以解開密文。在大多數的屬性加密系統中，只有單一授權中心負責發放所有的公鑰和私鑰，假如有許多個授權中心可以發放自己的公鑰和私鑰，這樣的屬性加密系統稱為多授權中心的屬性加密系統。屬性加密系統裡的存取控制是來自於秘密分享機制。在這篇論文中，我們提出了一個用在屬性加密系統和秘密分享機制的演算法，這個演算法增加了存取公式的表達性，跟之前的演算法比較，我們的演算法可以處理更多種類的存取公式。我們並實現了上述的演算法和一個多授權中心的屬性加密系統。最後，我們討論了許多可行的應用，這些應用和我們的實現都有高度的相關。

The Attribute-based encryption (ABE) scheme provides a fine-grained access control mechanism which is better than traditional public-key encryption schemes such as RSA and ElGamal. In an ABE scheme, the encryptor can specify an access formula that controls which private keys have the ability to decrypt the ciphertext. In most ABE schemes, there is only one authority who issues all private keys and public keys. If there are many authorities who issues their own private keys and public keys in an ABE scheme, the scheme is called ABE with multiple authorities. The access control mechanism in ABE schemes is from secret sharing schemes. In this thesis, we proposed an algorithm which is used both in secret sharing schemes and ABE schemes. Our algorithm provides more expressiveness in the access formula. Compared to the previous algorithm, our algorithm can handle more types of access formulae. Also, the algorithm and an ABE scheme with multiple authorities are implemented. Finally, we discuss applications that are highly related to our implementation.