Data file encryption and integrity verification method and system for untrusted server environment

The invention provides a data file encryption and integrity verification method and system for an untrusted server environment, and relates to the technical field of data privacy protection, and the method comprises the steps: 1) initializing a system; 2) generating public and private keys of a BGN homomorphic encryption algorithm; 3) constructing public and private keys of the data signature; 4)encrypting the data file by adopting a BGN homomorphic encryption algorithm public key; 5) respectively constructing labels for all file blocks in the data file according to the private key of the data signature; 6) uploading the set of encrypted files and labels to a cloud server; 7) sending a file integrity challenge to the cloud server to return a label and a file block sum; 8) verifying the label sum by using the file block sum and the public key of the data signature so as to judge the integrity of the ciphertext file stored in the cloud server. According to the method, a BGN homomorphicencryption algorithm and a