Research On Key Technologies Of Multi-Conditional Proxy Broadcast Re-encryption

With the diversified development of the Internet,cloud storage has become a necessary link for synchronizing files between different devices and users.However,the widely used encrypted file sharing method in cloud storage has the risk of key leakage.While cloud storage brings convenience,the security of shared files has been increasingly threatened.Proxy reencryption technology provides a more secure way to share encrypted files: When the ciphertext meets the conditions set by the principal,the semi-honest proxy can convert the principal's ciphertext into a new set of ciphertext directly,and the proxy cannot obtain any valuable information in this process.Starting from the access control mechanism of proxy re-encryption,this article introduces the access control strategy into the broadcast proxy re-encryption scheme and proposes two related schemes.Main research of the paper is as follows:(1)To solve the problem of single access control strategy in traditional conditional proxy re-encryption system,this paper proposes a multi-conditional proxy broadcast re-encryption scheme.This scheme reduces the access conditions to the bilinear pairing multiplication operation,and realizes multi-conditional access control without relying on the access control model.Moreover,this thesis constructs an anti-chosen ciphertext attack scheme based on bilinear pairings and proves its security in a random oracle model.(2)Aiming at the problem that bilinear pairing cannot be performed or logical operation,this paper proposes a fine-grained conditional proxy broadcast re-encryption scheme.Based on the research work(1),this scheme introduces an access tree to control the conversion conditions,which makes the ciphertext conversion conditions more flexible.To solve the problem that the multi-condition proxy broadcast re-encryption scheme relies on random oracles,this paper replaces part of the ideal hash function,and gives a security proof against chosen ciphertext attack under the standard model.(3)This thesis realizes the conditional proxy broadcast re-encryption schemes using pairing-based cryptography library and compares the schemes with other proxy re-encryption in theory and algorithm implementation.The results show that the proposed scheme has good practicality value.