Multi-user Attribute Based Searchable Encryption

Globalized services economy is increasingly adopting cloud computing in which applications, platforms, and infrastructre are available as services. Huge volume of data including sensitive data is outsourced and stored remotely in public clouds. There is a need for efficient protection of the privacy and security of users and their data without affecting its utility to authorized users. There needs to be a trade-off between data security and availability. Multi user encryption schemes provide partial solution by encrypting data and managing keys efficiently among the users but exposing the entire data accessible to all the users. But, in certain applications, the data need to be accessed by only specified users and they shall have access to only specifed parts of the data on a need to know basis. Ciphertext policy attribute based encryption supports keyword based search but require large amount of data for a single keyword thereby increasing the size and hence the cost of storage on the cloud. In this paper, we have proposed an encryption scheme which requires less storage space on the cloud but provides fine grained access control to authorized users. This is a hybrid scheme that combines the strenghts of both attribute based encryption and searchable encryption.