Abstract: Plaintext transmission is easily tampered with in distributed databases. To address the security risk, a multi-level control algorithm for secure access is proposed to distributed databases based on searchable encryption technology. The algorithm groups the authorized users according to the security level, and uses TF-IDF( Tem Frequency-Inverse Document Frequency) algorithm to calculate the weight of plaintext keywords, then uses AES (Advanced Encryption Standard) algorithm and round function to generate the key of the ciphertext, uses matrix function and inverse matrix function to encrypt the plaintext, and uploads the encryption results to the main server. And the Build Index algorithm is used to generate an index of ciphertext, and whether the user has access to ciphertext is reviewed based on the relevant attribute information of the user’s security level. After the review is passed, the user can issue a request for the number of ciphertext and keyword search. The server sends the ciphertext back to the user and decrypts it using a symmetric key method, achieving multi-level access control. The experimental results show that this method takes a short time in the encryption and decryption processes, and has good security access control performance.

Key words: searchable encryption technology, distributed database, security access control, clear text encryption