A Novel Approach for Searchable CP-ABE with Hidden Ciphertext-Policy

Abstract

Abstract. Ciphertext policy attribute based encryption (CP-ABE) is a technique in which a user with secret key containing attributes is only able to decrypt the message if the attributes in the policy match with the attributes in secret key. Therefore, CP-ABE is suitable for some interesting applications such as cloud computing which requires both security assurances and access control over encrypted data simultaneously. However, we observed that all existing CP-ABE schemes entail a limitation that, if an authorized user wants to search for an encrypted file having particular keywords, then he has to first download and then decrypt the file before searching for particular keywords. When applied to an application involving a cloud, because the number of files on the cloud is likely to be huge, all these process results in large overhead for user.Therefore, to overcome this limitation, we proposed a new searchable CP-ABE scheme in this paper, that allows the authorized user to check whether the ciphertext contains specific set of keywords or not, using his own token without decrypting the message. The label and keywords attached with ciphertext and secret key respectively, do not reveal any information about the data unless given the authorized token. In addition, our proposed scheme provides receiver anonymity also. The security analysis shows that privacy in this new solution is achieved with an overwhelmingly large probability. Equipping CP-ABE scheme with keyword-searching capability reduces the searching time of ciphertext having particular keywords. To the best of our knowledge ours is the first efficient collusion resistant searchable CP-ABE scheme with hidden ciphertext policy which uses few and fixed number of pairing operation in key word search as well as decryption algorithm.

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“…At present, attribute encryption [33] is mainly divided into ciphertext policy attributebased encryption (CP-ABE) [34][35][36][37][38][39][40][41][42][43][44] and key policy attribute-based encryption (KP-ABE) [45][46][47][48]. The difference between the two ABE systems is that one is to pair the access rules with the private key and the other is to encrypt the access rules and messages into ciphertext.…”

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