CN111444140A - CPBE-based file ciphertext fast searching method - Google Patents

Abstract

The invention discloses a file ciphertext fast search method based on CPBE, firstly, initializing a system and generating a system public parameter; secondly, the file generating equipment generates a file searching index according to the file attribute set and sends the file searching index to a searching server; then, the searching user generates a file searching trapdoor according to the searching attribute set and sends the file searching trapdoor to a searching server; and finally, the search server operates a search algorithm according to the search index and the search trapdoor to judge whether the file attribute set contains the search attribute set. The invention adopts an attribute-based encryption technology, integrates different attribute keywords through bilinear mapping, and provides a ciphertext search algorithm which is efficient and supports multi-attribute search.

Description

CPBE-based file ciphertext fast searching method

Technical Field

The invention relates to a CPBE-based file ciphertext fast searching method, and belongs to the technical field of searchable encryption.

Background

In 2000, Song et al proposed a searchable encryption concept and received widespread attention in academia. The meaning of searchable encryption is that the user sends encrypted data to a specific server, the server performs matching search on a search certificate and each encrypted file, and if matching is completed, the encrypted file is returned to the user. In the process of searching the ciphertext file, the server cannot acquire any information of the plaintext of the file. The searchable encryption technology requires the server to perform data memorability search on the ciphertext without decrypting the ciphertext, so that the confidentiality of the file is guaranteed while the search is performed. The searchable encryption technology essentially belongs to the function encryption technology, and the ciphertext generated by the searchable encryption technology is the function in the function encryption.

Although the searchable scheme at the time can complete a certain ciphertext search function, fine-grained access control is not supported. In addition, the retrieval efficiency of ciphertext search work completed through the public key cryptography is too low, and great expense is caused to the system, so that the students of cryptography introduce an attribute-based encryption mechanism to complete the ciphertext search work, and the performance of ciphertext search is improved through the characteristics of flexibility of attribute-based encryption and fine-grained access control.

Students introduce attribute-based encryption technology into searchable encryption technology, and fine-grained access control function is brought to the searchable encryption technology. However, the searchable encryption technology based on attribute-based encryption has high computational complexity, requires high computational performance of computing equipment, and is difficult to apply to the internet of things. In addition, the searchable encryption technology based on attribute-based encryption is difficult to perform multi-keyword search, and further design of an algorithm is required.

With the high-speed development of the ciphertext search technology, the ciphertext search not only ensures the privacy of the user, but also improves the retrieval efficiency of the user, and is gradually suitable for the current cloud era. However, to apply the searchable encryption technology to practical applications more widely, the algorithm needs to be applied to more scenes to achieve more functions.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a method for quickly searching a file Ciphertext based on CPABE (i.e. Ciphertext-Policy Attribute based encryption (CP-ABE) technology, wherein Chinese paraphrase is based on a Ciphertext strategy).

The technical scheme is as follows: the invention relates to a CPBE-based file ciphertext rapid searching method, which comprises the following steps of:

(1) initializing a system, and outputting a system public parameter PM and a master key MSK;

(2) generating a file search index, and calculating and outputting a search index In of the file;

(3) generating a file search trap door, and calculating and outputting a search trap door Tr of the search keyword set;

(4) and searching a file keyword set according to the search index and the search trapdoor.

Further, the specific method for calculating and outputting the search index In of the file In step (2) is as follows:

document keyword collection

A subset of a set of user attributes that is an encrypted user;

an m-th order polynomial is constructed using the random numbers a and k in the master key MSK:

g(x)＝a·(x-H(w₁)(x-H(w₂)…(x-H(w_m))+k

＝a_mx^m+a_m-1x^m-1+…a₁x+a₀

a_iis a polynomial in which xⁱFor coefficient of (2) of

Each attribute calculates a corresponding index member parameter F_i：

Wherein g is bilinear mapping generation element in the public parameter, c is parameter value in the main key, and the index is calculated to generate parameter W:

W＝g^ck

generating search index In ═ { W, F₁,F₂,…,F_m}。

Further, the specific method for calculating and outputting the search trapdoor Tr of the search keyword set in the step (3) is as follows:

search keyword set

The method is a subset of a user attribute set of a search user, and the user uses an attribute value required to be searched by the user as a search keyword set to generate a corresponding search trapdoor:

selecting a bilinear map Z_pRandom number d in the domain, for each i ∈ {0,1, …, m } in the search keyword set, calculating the corresponding trapdoor member parameter H_i：

And simultaneously calculating a trapdoor generation parameter T:

T＝h^dt

generating search trapdoor Tr ═ T, H₁,H₂,…,H_m}。

Further, the step (4) comprises the steps of:

(41) the system inputs a search trapdoor Tr and a search index In a server;

(42) calculating search algorithm parameters E₁，E₂：

(43) Calculating search result S ═ E₁/E₂。

Drawings

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a flow diagram of search index generation.

FIG. 3 is a flow chart of search trapdoors generation

Fig. 4 is a ciphertext search flow diagram.

Detailed Description

The invention will be further described with reference to the accompanying drawings. As shown in fig. 1, the present invention comprises the steps of:

step 1, system initialization: running Algorithm 1^λObtaining a set of bilinear mapping parameters:

choose one-way hash function H: {0,1} → Z_pThe generated public parameters are:

three random numbers a, c, k ∈ Z are selected_pThe master key is saved as follows:

MSK＝(a,c,k)

step 2, generating a file search index: document keyword collection

In order to encrypt the subset of the user attribute set of the user, the user encrypts the file attributes as search keys to generate search index values. An m-th order polynomial is constructed using the random numbers a and k in the master key MSK:

g(x)＝a·(x-H(w₁)(x-H(w₂)…(x-H(w_m))+k

＝a_mx^m+a_m-1x^m-1+…a₁x+a₀

for each i ∈ {0,1, …, m }, a corresponding index member parameter F is computed_i：

And simultaneously calculating an index generation parameter W:

W＝g^ck

constructing a search index In as:

In＝{W,F₁,F₂,…,F_m}

a search index generation flow diagram is shown in fig. 2.

Step 3, searching filesAnd (3) trap door generation: search user using search keyword set

And generating a search trapdoor. Search keyword set

The method is a subset of a user attribute set of a search user, and the user uses an attribute value required to be searched by the user as a search keyword set to generate a corresponding search trapdoor.

Selecting a random number d ∈ Z_pFor each i ∈ {0,1, …, m } in the set of search keywords, the corresponding trapdoor member parameter H is computed_i：

And simultaneously calculating a trapdoor generation parameter T:

T＝h^dt

the search trapdoor is constructed as follows:

Tr＝{T,H₁,H₂,…,H_m}

the search trapdoor generation flow chart is shown in fig. 3.

And 4, ciphertext search: the search server receives a search request and a search trapdoor Tr from a user, calculates whether a keyword set matched with the search trapdoor is contained in a keyword set of a search index, and returns a unique identification number of a file corresponding to the index value if the keyword set is contained in the keyword set of the search index. The system inputs a search trapdoor Tr and a search index In a server, and calculates a search algorithm parameter E₁，E₂：

E₂＝e(W,T)

The search results are calculated as:

if the search result S is 1, the index value contains a keyword set of the search trapdoors, the file corresponding to the index accords with the search condition, and the search server sends the unique file identification number corresponding to the index value to a search user; if S is 0, the keyword set in the index value is not matched with the keyword set in the search trapdoor, and the file does not meet the search requirement.

The ciphertext search flow diagram is shown in fig. 4.

The technical means disclosed by the invention are not limited to the technical means disclosed by the technical means, and also comprise technical schemes formed by equivalent replacement of the technical features. The present invention is not limited to the details given herein, but is within the ordinary knowledge of those skilled in the art.

Claims (4)

1. A CPBE-based file ciphertext fast searching method is characterized by comprising the following steps:

(1) initializing a system, and outputting a system public parameter PM and a master key MSK;

(2) generating a file search index, and calculating and outputting a search index In of the file;

(3) generating a file search trap door, and calculating and outputting a search trap door Tr of the search keyword set;

(4) and searching a file keyword set according to the search index and the search trapdoor.

2. The CPBE-based file ciphertext fast-search method according to claim 1, wherein the specific method for calculating and outputting the search index In of the file In step (2) is as follows:

document keyword collection

A subset of a set of user attributes that is an encrypted user;

an m-th order polynomial is constructed using the random numbers a and k in the master key MSK:

g(x)＝a·(x-H(w₁)(x-H(w₂)…(x-H(w_m))+k

＝a_mx^m+a_m-1x^m-1+…a₁x+a₀

a_iis a polynomial in which xⁱFor coefficient of (2) of

Each attribute calculates a corresponding index member parameter F_i：

Wherein g is bilinear mapping generation element in the public parameter, c is parameter value in the main key, and the index is calculated to generate parameter W:

W＝g^ck

generating search index In ═ { W, F₁,F₂,…,F_m}。

3. The CPBE-based file ciphertext fast search method according to claim 1, wherein the specific method for calculating and outputting the search trapdoor Tr of the search keyword set in the step (3) is as follows:

search keyword set

The method is a subset of a user attribute set of a search user, and the user uses an attribute value required to be searched by the user as a search keyword set to generate a corresponding search trapdoor:

selecting a bilinear map Z_pRandom number d in the domain, for each i ∈ {0,1, …, m } in the search keyword set, calculating the corresponding trapdoor member parameter H_i：

And simultaneously calculating a trapdoor generation parameter T:

T＝h^dt

generating search trapdoor Tr ═ T, H₁,H₂,…,H_m}。

4. The CPBE-based file ciphertext fast searching method according to claim 1, wherein the step (4) comprises the steps of:

(41) the system inputs a search trapdoor Tr and a search index In a server;

(42) calculating search algorithm parameters E₁，E₂：

(43) Calculating search result S ═ E₁/E₂。

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