Research And Application Of Searchable Encryption Schemes With Special Properties

With the development of science and technology,such as big data and cloud computing,Data users store data on cloud servers to reduce local storage and to meet functions such as data backup.Cloud servers are usually considered semi-trusted and users need to encrypt the data then upload it,but the searchability and accessibility of ciphertext data will be reduced as a result.Searchable encryption is an important technology to guarantee the retrievability of ciphertext in cloud servers and this technology provides a solution for retrieving ciphertext data in the cloud.The data owner encrypts the target data and uploads it to the cloud server,and the authorized data user generates the corresponding trapdoor,through which the data can be searched and obtained.However,the current public-key searchable encryption technology has problems,such as low computational performance,the data in cloud servers cannot be updated in real-time and the search results are not well verified.In this thesis,three searchable encryption schemes are constructed by combining key encapsulation,pseudorandom function,and inverted index.The main contributions of this thesis are as follows:An identity-based key encapsulation searchable encryption scheme is proposed.The scheme encrypts plaintext data using symmetric keys,encapsulates the symmetric keys using public key cryptography,and sends them to the server.Next,the server verifies the trapdoor and sends the key encapsulation value and the ciphertext to the corresponding data user,who uses the symmetric key and performs the decryption operation.The proposed scheme satisfies the indistinguishability under the random oracle model based on the Trapdoor Diffie-Hellman problem.After experimental comparison,the proposed scheme has an advantage in efficiency.A dynamic searchable encryption scheme with a double-layer structure satisfying both forward and backward security is proposed.The double-layer structure keeps the communication overhead low while ensuring forward and backward security,and further reduces the algorithm overhead by avoiding the bilinear pair operations in the encryption and decryption operations.The experimental results show that the scheme has advantages in terms of security and computational efficiency.A dynamic searchable encryption scheme with authentication based on a smart healthcare system is proposed,and the scheme satisfies both forward and backward security.The scheme is based on the principle of additive secret sharing,where each document containing a keyword is assigned a secret share to hide its entry.To achieve dynamic updates,each secret share stored in the client is shared recursively.If the secret can be reconstructed,it indicates that the search result is correct.This solution effectively secures the patient’s private data in the smart healthcare system,while adding validation to the search results and reducing the possibility of anomalous search results due to objective factors.