Attribute-Based Keyword Search With Constant Size Ciphertexts

In cloud computing,to keep their sensitive data confidential,users need to encrypt the data and outsource the ciphertexts to cloud servers.Therefore,whether users can search on encrypted data efficiently is important.Attribute-based keyword search(ABKS)is a public key encryption with keyword search scheme which enables users to search on ciphertexts and implements fine-grained access control and search authorization.In an ABKS scheme,a legal user can authorize a proxy to test whether a ciphertext includes some specific keywords without revealing any information about the content of sensitive data to the proxy.Existing ABKS schemes mainly focus on the realization of flexible access structures,while the computation cost and communication cost are linear with the number of required attributes.The expensive computation cost and communication cost are undesirable to the users who only have constrained computing power and storage space in cloud computing.Furthermore,it is necessary that an ABKS scheme should support efficient user revocation in cloud computing since the attributes of users often change.To resolve the above problems,this paper focuses on the research of attribute-based keyword search with constant size ciphertext and achieves the following results.1.Attribute-based keyword search with constant size ciphertext and monotonic access structure.The scheme captures some nice features:(1)It supports monotonic access structure;(2)The index encryption algorithm has constant computation cost;(3)The searchable ciphertexts are constant size;(4)The trapdoors for keywords are constant size;(5)The test algorithm has constant computation cost;(6)It supports efficient user revocation.2.Attribute-based keyword search with constant size ciphertext and non-monotonic access structure.This scheme captures several nice features:(1)It supports non-monotonic access structures;(2)The index encryption has constant computation cost;(3)The size of the searchable ciphertext is constant;(4)The size of the trapdoors for specific keywords generated by legal users is constant;(5)The computation cost of the test algorithm is constant;(6)It supports efficient user revocation.Compared with existing ABKS schemes,the proposed schemes have the following innovations:(1)The proposed schemes reduce the computation cost of existing ABKS schemes which is linear with the number of required attributes to be constant;(2)The proposed schemes reduce the communication cost of existing ABKS schemes which is linear with the number of required attributes to be constant.