Abstract
Cloud storage services，which can be regarded as a kind of typical service in cloud com-
puting，provides high-quality services and applications over the Internet．One of the biggest
merits of cloud storage is that users can access data in a cloud any time and any where，
using any device．However，allowing a cloud service provider(CSP)，whose purpose
is mainly for making a profit，to take the custody of sensitive data，raises underlying security
and privacy issues．To ensure the privacy and confidentiality of sensitive data from even inside
attackers such as a malicious system administrator of a database，a user herself may encrypt
the sensitive data before uploading the data into a database server．However，data encryption
makes it extremely difficult to search for a specific file in the ciphertext files．Searchable en-
cryption technology can be a good solution to this problem．Public key encryption search，as
one of the searchable encryption technologies，enables a user to search encrypted data without
revealing any information on the query and data，even to the database server．In this paper we
studied the technology of both Public Key Encryption with Keyword Search(PEKS) and Public
Key Encryption with Delegate Search(PKEDS)．The main results are as follows:
1 We proposed a new efficient trapdoor-indistinguishable public key encryption with key-
word search which satisfies the property of trapdoor indistinguishability and PEKS cipher-
text indistinguishability without using an additional secure channel．Moreover, we analysis the
efficiency and security of our scheme．
2 We proposed a Public Key Encryption with Delegated search．we present a refined
formulation for PKEDS and extend it to multi-server setting．Morever, we present a new con-
struction for PKEDS and prove its security in our security model．Compared with the original
scheme，our scheme is much more efficient．
Keywords: Searchable Encryption Cloud Computing Delegate Keyword Search
Public Key
