IBEET-AOK: ID-based encryption with equality test against off-line KGAs for cloud medical services

1 Introduction With the rapid development of cloud computing,more and more data are stored in cloud servers as cyphertexts for stor-age[1,2].However,it faces enormous challenges regarding ci-phertext analysis.For example,in the cloud medical services,authorized medical institutions(AMIs)need analyze medical records to figure out gender and age information on patients with the same disease.On account of privacy protection for pa-tients,hospitals should encrypt each medical record,and upload the ciphertext to the cloud server,followed by the application of public key encryption with equality test(PKEET)[3,4]to get the encrypted medical records with the same disease.However,frequent operations of equality testing will result in off-line key-word guessing attacks(KGAs)[5],thus making insider attack-ers snatch users'confidential information because the keyword space of diseases is far smaller than key space.