Secure and privacy preserving keyword searching cryptography

Using storage systems outside a company endanger data security. This leads users to encrypt their information for risk mitigation. Although encryption improves confidentiality, it causes inefficiency such as the encrypted data is not searchable. In this paper, data would be stored in a cloud storage provider (CSP) in a way that it is secure and simultaneously searchable. To this end, one of the state-of-the art encryption schemes secure and privacy preserving keyword searching (SPKS) has been employed. The encryption algorithm employs CSP for partially decryption of the cipher texts. Consequently, the client computational and communication overhead in decryption will be reduced. Although the CSP participates in the deciphering process, it cannot detect any information about the plaintext. In this paper we show that due to lack of client signature in the SPKS, an attack called forging attack is applicable on it. An improved version of SPKS has been introduced and the security of the proposed scheme is analyzed.