Research On Attribute Based Encryption Algorithms

These years, attribute-based encryption algorithm becomes a popular topic in the fieldof cryptography. An attribute-based Encryption scheme enables encipher to ascribe anexpressive access policy when encrypting. Every user will get secrete decryption keywhich depends on their attribute from an authorized third-party. Users’keys can decryptthe ciphertext if and only if their attributes meet requirements of ciphertext’s policy. Theprovablysecureattribute-basedencryptionschemeinmulti-authoritysenseandrevocableattribute-based encryption scheme has been researched in this dissertation. The mainresult is as follow.Adecentralizingkey-policyattributebasedencryptionalgorithmwithconstantcipher-text size and expressive policy has been proposed. Firstly, we provide formal definitionof its algorithm and security. Then, concrete algorithm is described. After that, we givea formal proof which reduces security of such algorithm to n-Diffie-Hellman exponentproblem. At last, efficiency, functionality and security comparisons between our resultand other relative algorithms have been provided. We point out that our algorithm has un-changed ciphertext size, supports any non-monotone access policy and can protect users’attribute privacy.Meanwhile, two revocable attribute-based encryption algorithms with full securityhave been proposed. They belongs to the notion of ciphertext-policy attribute encryptionand key-policy attribute-based encryption, respectively. In order to archive that, we con-struct a simple adaptively secure revocation scheme in the first step. This scheme is basedon composite order bilinear map and its adaptive security can be reduced to three staticcomplexity assumptions through the famous dual system encryption proof methodology.Next,wegivetheformaldefinitionforalgorithmandsecurityofrevocableattribute-basedencryption. We construct two revocable attribute-based encryption algorithms by usingthe revocation scheme. Then, we use dual system encryption proof methodology to provethat their security is based on aforementioned three static assumptions in standard model.Finally, the security, functionality and efficiency are analyzed.