Efficient and large universe ciphertext-policy attribute-based encryption with black-box traceability for ehealth

In the modern medical environment, massive application of electronic health systems has brought us great convenience. At the same time, the large and cumbersome data storage has become easier with the emergence of cloud computing. However, the emergence of shared platforms has also brought many security issues such as data loss and privacy exposures, especially the exposures of sensitive data by illegal users. In this paper we propose an efficient and large universe ciphertext-policy attribute-based encryption (CP-ABE) scheme with black-box traceability for the collaborative eHealth system. It is of a higher efficiency by reducing greatly the cost of encryption and decryption operations. We prove the security of our new scheme under the q-parallel BDHE assumption in the standard model.