Year

2016

Degree Name

Doctor of Philosophy

Abstract

Access control plays an important role in many information systems. Embedding policy-based access control into modern encryption schemes is an interesting but challenging task that has been intensively studied by the cryptographic research community in recent years. Furthermore, most of encryption schemes require not only the guarantee of security, but also the efficiency in terms of computational and communication cost when producing ciphertext and secret key.

In this thesis, we study Functional Encryption comprising its subclasses such as Attribute Based Encryption, Hidden Vector Encryption, and Inner Product Encryption. We boost the advantage of these encryption schemes by improving their performance, which is critical for real applications. We also consider the user anonymity in these encryption systems in order to protect user privacy, which is very important nowadays.

This thesis has five major contributions. First, we construct two Attribute Based Encryption schemes for achieving the constant ciphertext size and hidden ciphertext policy. Second, by combining Attribute Based Encryption and Broadcast Encryption, we construct Attribute Based Broadcast Encryption schemes with short ciphertext and short decryption key. Third, We also explore the anonymity of Attribute Based Broadcast Encryption supporting multi-gate access structures. Fourth, we propose two ciphertext policy hidden vector encryption schemes with constant-size ciphertext, and attribute hiding. Both of our proposed schemes achieve the efficiency and exibility. Finally, we construct a new type of fuzzy public key encryption, called Edit Distance-based Encryption, based on the Edit Distance which is a very useful tool to measure the similarity between two strings.

In our constructions, we define the access policy by applying the Boolean AND Gates Access Structure with positive, negative attributes including wildcard; OR- AND Gates with positive, negative attributes. We also develop techniques to bridge Attribute Based Encryption, Attribute Based Broadcast Encryption with Inner Product Encryption, and then use the latter to achieve the goal of hidden access policy. All of our proposed schemes are proven secure under standard assumptions.

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