File storage method, file search method and file storage system based on public-key encryption with keyword search

A file storage method based on public-key encryption with keyword search, characterized by comprising the following steps:

• receiving a user file storage request sent from a data possessor and acquiring access control attribute information for access to a user file, security level parameters and a keyword set of the user file;
• generating a file attribute vector of the user file by means of the access control attribute information and the keyword set;
• acquiring a public-secret key pair used for encrypting the file attribute vector from a pre-generated key space according to the access control attribute information;
• encrypting the file attribute vector by means of a public key in the public-secret key pair according to the security level parameters to obtain a ciphertext corresponding to the file attribute vector;
• and transmitting the ciphertext corresponding to the file attribute vector and a ciphertext of the user file to a preset storage server;
• wherein the step of encrypting the file attribute vector by means of the public key in the public-secret key pair according to the security level parameters to obtain the ciphertext corresponding to the file attribute vector comprises the sub-steps:
• calculating a security functional parameter used for recognizing an encryption security level according to the security level parameters;
• and encrypting the file attribute vector through an encryption method corresponding to the encryption security level according to the security functional parameter obtained through the calculation;
• wherein the step of calculating the security functional parameter used for recognizing the encryption security level according to the security level parameters comprises the sub-step:
• calculating the security functional parameter Sec according to a formula
• Sec
• =
• (
• w
• 1
• I
• +
• w
• 2
• F
• )
• ⁢
• (
• 1
• -
• ρ
• Sec
• 3
• )
• +
• ρ
• Sec
• 3
• ,
• wherein I and F are the security level parameters, w1 and W2 are weights corresponding to I and F and Psec3, is a threshold corresponding to a preset basic encryption security level;
• wherein the step of encrypting the file attribute vector through the encryption method corresponding to the encryption security level according to the security functional parameter obtained through calculation comprises the sub-steps:
• when the security functional parameter Sec meets ρSec2≤Sec≤ρSec1, determining that the encryption security level corresponding to the security functional parameter is a second encryption security level, wherein Psec1 and Psec2 are thresholds corresponding to progressively-increased encryption security levels;
• encrypting the file attribute vector by means of the public-key in the public-secret key pair through prime-order bilinear pairing operation to obtain the ciphertext corresponding to the file attribute vector;
• and conducting secondary encryption corresponding to the second encryption security level on the ciphertext of the file attribute vector to obtain a secondarily-encrypted ciphertext of the file attribute vector.