Timestamped Conjunctive Keyword-Searchable Public Key Encryption

To realize ubiquitous computing, data should be able to be accessed from anywhere at anytime. However, for security purpose, we need to encrypt the data so that the attackers cannot obtain any information from the server. Nevertheless, the user should be able to use keywords to search and retrieve required data. To this end, we propose a timestamp based conjunctive keyword searchable public key encryption scheme. Our construction is semantically secure against adaptive chosen keyword attacks and off-line guessing attacks, based on the decision Diffie-Hellman assumption.