Cryptanalysis on the Anonymity of Li et al.'s Ciphertext-Policy Attribute-Based Encryption Scheme

摘要

Attribute-based encryption is a very powerful primitive in public-key cryptography. It can be adopted in many applications, such as cloud storage, etc. To further protect the privacy of users, anonymity has been considered as an important property in an attribute-based encryption. In an anonymous attribute-based encryption, the access structure of a ciphertext is hidden from users. In this paper, we find an attack method against Li et al.'s anonymous attribute-based encryption schemes. The proposed attack uses an "invalid attribute key" to recover the hidden access structure of a given ciphertext. No information of the master secret key nor private keys are necessary in our attack.