Ciphertext Retrieval With Identity Bidirectional Authentication and Matrix Index in IoT

Ciphertext retrieval for cloud-based Internet of Things has been widely explored with the increasing popularity of cloud computing. However, in most existing solutions, the security and efficiency of the retrieval process are difficult to achieve simultaneously. To this end, we develop a novel secure matrix index, and we utilize identity-based encryption to encrypt keywords and homomorphic encryption to encrypt matrix values. The former can guarantee the security of the keyword, and the latter can realize the efficiency of the operation while ensuring safety. Then, we develop an identity-based bidirectional authentication algorithm to ensure that only authenticated users can retrieve ciphertext. In addition, we use different scoring formulas to calculate the relevance scores of documents with different lengths, ensuring that the documents are appropriately returned to users. Finally, we design a new retrieval structure to protect the privacy of the correspondence between keywords and ciphertexts. The security proof shows that the index and trapdoor can resist chosen keyword attack and keyword Guessing attack. The extensive simulation shows that our scheme is efficient.