Abstract:

Conditional proxy re-encryption can grant fine-grained authorization to ciphertext according to conditional information. Most of the existing conditional proxy re-encryption schemes are based on traditional public key infrastructure or identity public key, therefore bringing the problems of certificate management and key escrow. To solve these problems, a new certificateless threshold conditional proxy re-encryption scheme is constructed, in which the conditional information is added when the original ciphertext and re-encryption key are generated, and the proxy node verifies the condition compliance before re-encryption to ensure that only the matching ciphertext can be re-encrypted. Threshold technology is used to protect re-encryption key and private key. Theoretical analysis shows that the proposed scheme is able to resist two types of adversary attacks,the first type-I adversary replaces the user's public key and the type-II adversary holds the system's master key.  The simulation results demonstrate that the proposed scheme has high efficiency in key operations such as re-encryption key generation and re-encryption, therefore, providing the basis for ciphertext sharing in applications such as distributed cloud storage.

Key words: conditional proxy re-encryption , certificateless , threshold , distributed data sharing