公開金鑰可搜尋多關鍵字之加密系統

Abstract

使用者將加密後的私密資料儲存至位於網際網路上的資料儲存伺服器已成為趨勢。有很多應用依賴具有強大運算能力的伺服器根據關鍵字搜尋加密文件，可搜尋之加密系統因此成為重要的技術。對於加密文件中搜尋關鍵字，此系統提供有效率的儲存與計算方式，並且無需解密金鑰。在可搜尋之加密系統的研究之中，比起對稱金鑰可搜尋之加密系統，公開金鑰可搜尋之加密系統較為被重視，因其支持多使用者的環境設定。另一方面，搜尋功能如多關鍵字之查詢的改進也已被深入探討。在這篇論文中，我們概括論述了重要的公開金鑰可搜尋之加密系統。接著我們提出一個公開金鑰可搜尋多關鍵字之加密系統，提供讓使用者在不透漏解密金鑰的情況下分享加密文件之功能，以及要求伺服器在加密之文件中搜尋多個關鍵字(〖KW〗_1⋀⋯⋀〖KW〗_w )，並且不洩漏任何單一關鍵字的資訊。我們的搜尋之加密系統基於雙線性配對之密碼系統，比起傳統RSA公開金鑰加密系統具有更短的密鑰長度，提高計算上的效能。

Currently, there has been a trend for users to store their encrypted private data over the Internet on a data server. Most applications rely on the data server with powerful computing power to perform searching on those encrypted data under the circumstances that server cannot access the plaintext of the data. The searchable encryption therefore becomes a crucial technique that supports searching functionality over encrypted data. Searchable encryption provides storage and computing efficiency for searching on certain keywords without requiring the decryption key. Researchers have been focused on the public key searchable encryption since it supports for multi-user settings and is considered more suitable for actual use than symmetric key searchable encryption. On the other hand, improving the searching functionality such as supporting conjunctive queries and other types of queries has been deeply studied. In this thesis, we survey the prominent public key searchable encryption schemes. Then we propose our design of public key searchable encryption with conjunctive queries that allows the users sharing the encrypted data among multiple users without sharing the decryption keys, as well as sending arbitrary conjunctive queries (〖KW〗_1⋀⋯⋀〖KW〗_w ) to the server without leaking information of any individual conjuncts. Our design of searchable encryption is based on bilinear pairing based cryptography, which implies it requires shorter key size than the traditional RSA public-key encryptions and implies improvement of efficiency.