Improved secure server-designated public key encryption with keyword search

Cloud storage service serves the need of data sharing between multiple parties. Cloud storage services allow the data owners to outsource their encrypted records to store over cloud storage servers and authorizes multiple users to access these files. Searching over encrypted data at cloud environment was made possible by various searchable schemes. Many of such schemes has its own limitations and security concerns. Existing schemes suffers from ON-KGA in which a malicious launches a keyword guessing attack to find the keyword used for generating the trapdoor. In this paper, we introduce a scheme which is immune to online Keyword guessing attacks(ON-KGA) in an environment where a server can be malicious. We propose a nonce based scheme in which a nonce is added with the keyword, thereby removing the weakness of ON-KGA, we also enhanced the existing security model for TD-IND.