Efficient ID-Based Proxy Pre-Encryption Scheme for Data Sharing in Cloud

In cloud computing, to ensure the outsourced data's security, the data needs to be encrypted. To achieve the outsourced data sharing, it is very difficulty to download and encrypt for the resource-constrained user. Proxy re-encryption is an alternative way to reduce computation cost and communication overhead for the user since identity-based proxy re-encryption (ID-PRE) schemes allow a proxy to translate an encryption under Alice's identity into one computed under Bob's identity without being able to learn the plaintext. The property makes identity-based proxy re-encryption play very important role in cloud storage. In this paper, we propose a novel identity-based proxy re-encryption scheme, and show that the scheme is proven to be secure in the random oracle. The security is related to the decisional bilinear Diffie-Hellman problem. And our scheme can realize the user's anonymity, that is to say, given re-encryption keys and ciphertext, an adversary cannot learn decryptor's identities.