WO2020133032A1

WO2020133032A1 - Multi-user ciphertext search method capable of preventing forgery

Info

Publication number: WO2020133032A1
Application number: PCT/CN2018/124205
Authority: WO
Inventors: 刘宏伟; 吴楚欣; 张鹏
Original assignee: 深圳技术大学（筹）
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2020-07-02

Abstract

Disclosed is a multi-user ciphertext search method capable of preventing forgery. The method is adopted to avoid a situation in which each user having a public key is disguised as a data owner to encrypt and upload data. The method comprises: using a symmetric key to encrypt a file so as to generate a first file ciphertext, generating a first key for file extraction, and uploading the first file ciphertext to a cloud server; generating an index set and an index array of the first file ciphertext, encrypting the first key to obtain a second ciphertext, and uploading the encrypted index of the first file ciphertext to the cloud server; generating a second key, and sending the second key to a user; the user selecting a search keyword set, and using the second key to decrypt the second ciphertext so as to obtain the first key, generating a search trapdoor according to the search keyword set, and sending the search trapdoor to the cloud server; the cloud server using the search trapdoor to search for a search result set, and returning the search result set to the user; and the user extracting a first file ciphertext set, and using a corresponding symmetric key to perform decryption. The method improves the security of data involved in cloud storage and cloud computing.

Description

Multi-user ciphertext search method capable of preventing forgery

Technical field

The invention relates to the technical field of information security, in particular to a multi-user ciphertext search method capable of preventing forgery.

Background technique

With the development of Internet technology, current cloud computing technology has powerful computing and storage capabilities, and in order to reduce the cost of data storage and management, enterprises and individuals are increasingly inclined to upload data to cloud servers; however, such as health data , Financial statements, e-mail and other sensitive data uploaded to the cloud server will bring a series of privacy issues; using encryption technology to process data can ensure the confidentiality of the data, but the availability and flexibility of the encrypted data will be reduced, in a large number of files Searching for specific data or files can be extremely difficult.

In the prior art, the searchable encryption technology can solve the above-mentioned problems, and the searchable encryption technology can search for specific keywords in the encrypted data; at present, most searchable encryption methods are based on single-user search under a symmetric encryption system Mode, and data sharing under the single-user model requires the data owner to provide search keys or generate search traps for authorized users online at all times. It can be seen that the single-user search mode cannot meet the situation where a large amount of data needs to be shared; Controlling the implementation of the multi-user model can limit the user's search authority, without requiring the data owner to be online at all times, which solves the defect of the single-user model.

technical problem

Due to the characteristics of public key encryption and private key decryption in access control, each user with a public key has the possibility of forging data owner data, so access control still has the problem of low data security.

Technical solution

In order to achieve the above object, a first aspect of the present invention provides a multi-user ciphertext search method capable of preventing forgery, including: a data owner encrypts a file with a symmetric key to generate a first file ciphertext, and generates a first Key, and upload the first file ciphertext to the cloud server; the data owner generates the index set and index array of the first file ciphertext, encrypts the first key using the attribute-based encryption scheme to obtain the second ciphertext, and The encrypted index of the ciphertext of the first file is uploaded to the cloud server; the private key generator PKG generates a second key corresponding to the user according to the user attribute set and sends it to the user; the user selects the search keyword set; the user uses the attribute-based encryption scheme Use the second key to decrypt the second ciphertext to get the first key; the user generates a search trapdoor based on the search keyword set and sends it to the cloud server; the cloud server uses the search trapdoor to search for the search results corresponding to the keyword set Set and return to the user; the user extracts the first file ciphertext set corresponding to the search result set, and decrypts using the symmetric key.

Beneficial effect

Different users have different attribute sets, which can generate different second keys for different users, so that each user's second key can only decrypt the encrypted index of the first ciphertext file that meets its strategy; the user is in When generating an encrypted index of the ciphertext of the first file, a pair of public and private keys is generated, and the private key is used as an element of the encrypted index, and the public key is shared with other users for search, so that other users cannot forge other users’ second keys Data improves the security of data involved in cloud storage and cloud computing.

BRIEF DESCRIPTION

1 is a schematic block diagram of a flow of a multi-user ciphertext search method that can prevent forgery according to the present invention;

2 is a schematic block diagram of the structure of the electronic device of the present invention.

Best Mode of the Invention

A first aspect of the present invention provides a multi-user ciphertext search method capable of preventing forgery, including: a data owner encrypts a file with a symmetric key to generate a first file ciphertext, generates a first key for extracting the file, and The first file ciphertext is uploaded to the cloud server; the data owner generates the index set and index array of the first file ciphertext, uses the attribute-based encryption scheme to encrypt the first key to obtain the second ciphertext, and encrypts the first file ciphertext The encrypted index is uploaded to the cloud server; the private key generator PKG generates a second key corresponding to the user according to the user attribute set and sends it to the user; the user selects the search keyword set; the user uses the attribute-based encryption scheme to use the second key Decrypt the second ciphertext to obtain the first key; the user generates a search trapdoor according to the search keyword set and sends it to the cloud server; the cloud server uses the search trapdoor to search for the search result set corresponding to the keyword set and returns it to the user ; The user extracts the first file ciphertext set corresponding to the search result set, and decrypts it using a symmetric key.

Further, the search method further includes: generating all keyword sets; generating a file set; and generating a symmetric key set of the first file ciphertext.

Further, the generation of the search trapdoor includes: verifying the second key, if the second key satisfies the access strategy, it is successfully decrypted, and if the second key does not satisfy the access strategy, a null value is returned; After successful decryption, generate the ciphertext of the keyword sent to the cloud server; generate a third key based on the keyword; generate a counter and calculate the trapdoor element until the server stops, then stop calculating the trapdoor element.

Further, the index set and index array for generating the ciphertext of the first file include: defining an anti-collision hash function; defining a pseudo-random function, and randomly selecting a first key according to the pseudo-random function; and generating a keyword set Indexed index array; generate the first empty set; generate the key set index ciphertext; fill the first empty set with the key set index ciphertext to form the index set; based on the first key, access policy, and the system-generated public key The key forms a second ciphertext; an encrypted index of the first file ciphertext is generated according to the index set, the index array, and the second ciphertext.

Further, the filling of the first empty set to form an index set includes: defining security parameters; defining a bilinear group with prime order and generator; randomly selecting integers within the prime order and calculating keyword ciphertext; initialization The first key, and randomly select the security parameter as an integer within the prime order; initialize the counter according to a random order; calculate the index ciphertext, encrypt the initialized first key, and define the index number; define the index of the index set Elements, and calculate the index set elements according to the generator, the initialized first key, the random number, and the index elements; calculate all the index set elements according to the counter.

Further, the index array for generating a key set index includes: generating an empty list; adding index elements and generators to the power of the index to the empty list in an array manner to generate an index array.

Further, using the search trapdoor to search the search result set corresponding to the keyword set includes: generating a second empty set; defining a verification formula, and calculating the keyword ciphertext and generator as elements of the formula, If the result of the calculation is equal to the result of the trapdoor, the index set is assigned to the second empty set; the index elements and generator indexes are retrieved from the second empty set according to the current count of the counter An array formed by several powers; determine whether the index element belongs to the index set; if the index element belongs to the index set, merge the index element into the search result set.

Further, the user extracting the first file ciphertext set corresponding to the search result set and decrypting using the corresponding symmetric key includes: decrypting the search results in the search result set according to the first key, obtaining the file identifier and Symmetric encryption key; send the file identifier to the cloud server to obtain the first file ciphertext returned by the cloud server, and use the corresponding symmetric key to extract the file corresponding to the first file ciphertext.

A second aspect of the present invention provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the computer program When any of the above methods are implemented.

A third aspect of the present invention provides a computer-readable storage medium on which a computer program is stored, characterized in that, when the computer program is executed by a processor, any one of the methods described above is implemented.

Embodiments of the invention

In order to make the purpose, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the drawings in the embodiments of the present invention. Obviously, the description The embodiments are only a part of the embodiments of the present invention, but not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

Please refer to FIG. 1, which is a multi-user ciphertext search method capable of preventing forgery, including: S1, a data owner encrypts a file with a symmetric key to generate a first file ciphertext, and generates a first key for extracting a file, Upload the first file ciphertext to the cloud server; S2, the data owner generates the index set and index array of the first file ciphertext, encrypts the first key using the attribute-based encryption scheme to obtain the second ciphertext, and then An encrypted index of a file ciphertext is uploaded to the cloud server; S3, the private key generator PKG generates a second key corresponding to the user according to the user attribute set and sends it to the user; S4, the user selects the search keyword set; S5, the user Use the attribute-based encryption scheme to decrypt the second ciphertext using the second key to obtain the first key; S6, the user generates a search trapdoor based on the search keyword set and sends it to the cloud server; S7, the cloud server uses the search trapdoor search The search result set corresponding to the keyword set is returned to the user; S8, the user extracts the first file ciphertext set corresponding to the search result set and decrypts using the symmetric key.

In this embodiment, a pair of public and private keys are generated when the index is encrypted, the private key is used as an element of the encrypted index, and the public key is shared with other users for search.

In this embodiment, the search method further includes: generating all keyword sets; generating a file set; generating a symmetric key set of the first file ciphertext. By generating a keyword set, a file set, and a symmetric key set, the key Words, files, and symmetric keys are collected separately, so that when using the search method provided in this application, keywords, files, and symmetric keys can be quickly found in the corresponding set, thereby improving search efficiency.

Generating search trapdoors includes: verifying the second key, if the second key satisfies the access strategy, it will be successfully decrypted, if the second key does not meet the access strategy, it will return a null value; after successful decryption, generate and send to the cloud server The keyword ciphertext; generate the third key according to the keyword; generate a counter and calculate the trapdoor element until the server stops, then stop calculating the trapdoor element.

Set the attribute set to S for legitimate users to keyword sets

Perform a search and assume that w ₁ is the keyword with the lowest frequency in the search keyword set. Then, the user requests the second ciphertext C from the cloud server, and generates the second key SK←ABE.KeyGen(MSK,S) through the private key generator PKG. Enter C, SK,

Output stag,xtoken[1],xtoken[2],…, trapdoor generation algorithm

The specific description is as follows: The user calculates k←ABE.Decrypt(C,SK). If the user's attribute S satisfies the index's access strategy Γ, it is successfully decrypted and returns k; otherwise, it returns null; the message (stag, xtoken[1], xtoken[2],...) sent to the server is defined as: key generation The ciphertext stag'←F(k,w ₁ ), stag←e(g ^s ,H ₁ (stag')), generate the key k ₁ ←F(k,1||w ₁ ), generate and run the counter c, and make c=1, 2, ... until the server stops running, and for i=2,...,n, calculate the trapdoor element xtoken[c,i]←P(k ₁ ,c)·(k, 1||w _i ), so there is xtoken[c]←(xtoken[c,2],xtoken[c,3],…,xtoken[c,n]), the search trapdoor algorithm described above generates a search trapdoor.

Generating the encrypted index of the ciphertext of the first file includes: defining a collision-resistant hash function; defining a pseudo-random function, and randomly selecting the first key according to the pseudo-random function; generating an index array of key set indexes; generating a first empty set ; Generate the keyword set index ciphertext; fill the first empty set with the keyword set index ciphertext to form the index set; form the second ciphertext based on the first key, access strategy, and the public key generated by the system; according to the index set, index The array and the second ciphertext generate an encrypted index of the ciphertext of the first file.

In order to ensure the confidentiality of outsourced files, a symmetric encryption algorithm SE=(Enc, Dec) is defined. The data owner encrypts f _i with r _i before building the index, to obtain the ciphertext ct _i ←SE.Enc(r _i , f _i ) (i=1, 2, L, d), and upload the ciphertext to the cloud server. In order to implement access control, the data owner needs to set the access control authority before uploading the data, and define the ciphertext access control scheme used as the attribute-based encryption scheme ABE=(Setup, Encrypt, KeyGen, Decrypt). Enter the system security parameter λ and the global attribute set N, PKG run (PK, MSK) ←ABE.Setup(1 ^λ ,N). Define the pseudo-random function PRF F:{0,1} ^λ ×{0,1} ^λ →{0,1} ^λ ,PRPP:{0,1} ^λ ×{0,1} ^λ →{0,1} ^λ ; Use the ciphertext database initialization algorithm EDBSetup(DB) to input the database DB and output the encrypted index EDB of the ciphertext. The specific description is as follows: randomly select the first key k for PRF F and express DB as

Define T as a set of keywords

Indexed empty array; defines XSet as an empty set; for each

Define t as an empty list, randomly select s ∈ Z _p , and calculate the keyword ciphertext, stag _w '←F(k,w), stag _w ←H ₁ (stag' _w ) ^s . Open g ^s , initialize the first key k ₁ ←F(k,1||w), randomly choose γ∈Z _p , for all id _i ∈DB(w), initialize the counter c←0 in random order, then: Calculate the index cipher text rind←P(k,id _i ||r _i ), encrypt k ₁ to get z←P(k ₁ ,c)·γ ^-1 , and define y←rind·z ^-1 , convert (rind, g ^y ) Add to t, define xtag as XSet is an element, calculate

Add xtag to XSet, c←c+1, T[stag _w ]←t, where Γ is the access strategy; output EDB=(XSet, T, C).

Filling the first empty set to form an index set includes: defining security parameters; defining a bilinear group with prime order and generator; randomly selecting integers within prime order and calculating key ciphertext; initializing the first key and randomizing Select the security parameter as an integer within the prime order; initialize the counter according to a random order; calculate the index ciphertext, encrypt the initial first key, and define the index number; define the index elements of the index set, and according to the generator, initialize the first The key, random number, and index elements are used to calculate the index set elements; all the index set elements are calculated according to the counter.

The index array for generating the keyword collection index includes: generating an empty list; adding the index power of the index element and generator to the empty list in an array manner to generate the index array.

Using search trapdoors to search the search result set corresponding to the keyword set includes: generating a second empty set; defining a verification formula, and calculating the keyword ciphertext and generator as elements of the formula. If the results of the gates are equal, the index set is assigned to the second empty set; according to the current count of the counter, the index element and the array of generator index powers are retrieved from the second empty set; determine whether the index element belongs to the index set, If the index element belongs to the index set, the index element is merged into the search result set.

The cloud server executes the search algorithm, enters trapdoors (stag, xtoken[1], xtoken[2],...) and EDB, returns the search results l, and the search algorithm Search(stag,(xtoken[1],xtoken[2],... ), EDB) are described as follows: define l, t as an empty set; verify whether the equation e(stag _w , g) = stag is true, if it is true, then t=T[stag _w ]; otherwise, return null; for c =1,2,...,|t|, retrieve from the c-th tuple in t (rand,g ^y ), if for

Let l←l∪rind.

The user extracts the first file ciphertext set corresponding to the search result set, and decrypts using the corresponding symmetric key includes: decrypting the search results in the search result set according to the first key, obtaining the file identifier and the symmetric encryption key Sending the file identifier to the cloud server to obtain the first file ciphertext returned by the cloud server, and extracting the file corresponding to the first file ciphertext with the corresponding symmetric key.

The user executes the extraction algorithm on the client, enters the search result l and the first key k, and returns the search result. The extraction algorithm Retrieve (l, k) is described as follows: The user decrypts the search result l with the first key k, and obtains the document id _i and the corresponding key r _i , for rind ∈ l: calculate (id _i ||r _i )←SE.Dec(k,rind), return (id _i ,r _i ); send id _i to the cloud server, Obtain the ct _i =SE.Enc(r _i ,f _i ) returned by the cloud server, and extract the file f _i =SE.Dec(r _i ,ct _i ) with the corresponding key r _i .

An embodiment of the present application provides an electronic device. Please refer to 2. The electronic device includes: a memory 601, a processor 602, and a computer program stored on the memory 601 and executable on the processor 602. The processor 602 executes the computer program At this time, the anti-counterfeiting multi-user ciphertext search method described in the foregoing embodiments of FIG. 1 to FIG. 4 is implemented.

Further, the electronic device further includes: at least one input device 603 and at least one output device 604.

The memory 601, the processor 602, the input device 603, and the output device 604 are connected via a bus 605.

The input device 603 may specifically be a camera, a touch panel, a physical button, a mouse, or the like. The output device 604 may specifically be a display screen.

The memory 601 may be a high-speed random access memory (RAM, Random Access Memory) memory, or may be a non-volatile memory (non-volatile memory), such as a disk memory. The memory 601 is used to store a set of executable program codes, and the processor 602 is coupled to the memory 601.

Further, an embodiment of the present application further provides a computer-readable storage medium. The computer-readable storage medium may be provided in the electronic device in each of the foregoing embodiments, and the computer-readable storage medium may be as shown in FIG. 2 described above. The memory 601 in the embodiment is shown. A computer program is stored on the computer-readable storage medium, and when the program is executed by the processor 602, the multi-user ciphertext search method that can be prevented from forgery described in the foregoing method embodiments is implemented.

Further, the computer storable medium may also be various media that can store program codes, such as a U disk, a mobile hard disk, a read-only memory 601 (ROM, Read-Only Memory), RAM, a magnetic disk, or an optical disk.

In the several embodiments provided in this application, it should be understood that the disclosed device and method may be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a division of logical functions. In actual implementation, there may be other divisions, for example, multiple modules or components may be combined or Can be integrated into another system, or some features can be ignored, or not implemented. In addition, the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or modules, and may be in electrical, mechanical or other forms.

The modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, that is, they may be located in one place, or may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist alone physically, or two or more modules may be integrated into one module. The above integrated modules can be implemented in the form of hardware or software function modules.

If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention essentially or part of the contribution to the existing technology or all or part of the technical solution can be embodied in the form of a software product, the computer software product is stored in a storage medium , Including several instructions to enable a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code .

It should be noted that, for the convenience of description, the foregoing method embodiments are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the sequence of actions described. Because according to the invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

In the above embodiments, the description of each embodiment has its own emphasis. For a part that is not detailed in an embodiment, you can refer to the related descriptions of other embodiments.

The above is a description of a multi-user ciphertext search method that can be prevented from forgery provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, the specific implementation and application scope may change. In summary, the content of this specification should not be construed as limiting the invention.

Industrial applicability

It solves the technical problem of low data security in the access control of the multi-user model in the prior art.

Claims

A multi-user ciphertext search method with anti-counterfeiting features, including:

The data owner encrypts the file with a symmetric key to generate the first file ciphertext, generates the first key for extracting the file, and uploads the first file ciphertext to the cloud server;

The data owner generates the index set and index array of the first file ciphertext, encrypts the first key using the attribute-based encryption scheme to obtain the second ciphertext, and uploads the encrypted index of the first file ciphertext to the cloud server;

The private key generator PKG generates a second key corresponding to the user according to the user attribute set and sends it to the user;

The user selects a set of search keywords;

The user uses the attribute-based encryption scheme to decrypt the second ciphertext using the second key to obtain the first key;

The user generates a search trapdoor based on the search keyword set and sends it to the cloud server;

The cloud server uses the search trapdoor to search the search result set corresponding to the keyword set and returns it to the user;

The user extracts the first file ciphertext set corresponding to the search result set and decrypts it using a symmetric key.
The anti-counterfeiting multi-user ciphertext search method according to claim 1, wherein:

The search method further includes: generating all keyword sets;

Generate a file set; generate a symmetric key set of the first file ciphertext.
The anti-counterfeiting multi-user ciphertext search method according to claim 1, wherein:

The generating search trapdoors includes:

Verify the second key, if the second key satisfies the access policy, then decrypt successfully, and if the second key does not satisfy the access policy, return a null value;

After successful decryption, generate the keyword ciphertext sent to the cloud server;

Generate a third key based on keywords;

Generate a counter and calculate trapdoor elements until the server stops, then stop counting trapdoor elements.
The anti-counterfeiting multi-user ciphertext search method according to claim 3, characterized in that

The index set and index array for generating the ciphertext of the first file include:

Define the anti-collision hash function;

Define a pseudo-random function, and randomly select the first key according to the pseudo-random function;

Generate an index array of key collection indexes;

Generate the first empty set;

Generate the ciphertext of the keyword collection index;

Filling the first empty set with a key set index ciphertext to form an index set;

Form the second ciphertext according to the first key, the access strategy and the public key generated by the system;

An encrypted index of the first file ciphertext is generated according to the index set, the index array, and the second ciphertext.
The anti-counterfeiting multi-user ciphertext search method according to claim 4, wherein:

Said filling the first empty set to form an index set includes:

Define safety parameters;

Define bilinear groups with prime order and generators;

Randomly select integers within prime order and calculate keyword ciphertext;

Initialize the first key, and randomly select the security parameter as an integer in prime order;

Initialize the counter according to random order;

Calculate the index ciphertext, encrypt the initial first key, and define the index number;

Define the index elements of the index set, and calculate the index set elements according to the generator, the initialized first key, the random number, and the index elements;

Calculate all the index set elements according to the counter.
The anti-counterfeiting multi-user ciphertext search method according to claim 5, characterized in that

The index array for generating the keyword collection index includes:

Generate an empty list;

Add the index elements and the index of the generator to the empty list as an array to generate an index array.
The anti-counterfeiting multi-user ciphertext search method according to claim 5, characterized in that

The search result set corresponding to the keyword set using the search trapdoor includes:

Generate the second empty set;

Define a verification formula, and calculate the keyword ciphertext and generator as elements of the formula, and if the result of the calculation is equal to the result of the trapdoor, assign the index set to the second empty set ;

Retrieving an array of index elements and generators to the power of the index from the second empty set according to the current count of the counter;

Determine whether the index element belongs to the index set. If the index element belongs to the index set, merge the index element into the search result set.
The anti-counterfeiting multi-user ciphertext search method according to claim 1, wherein:

The user extracting the first file ciphertext set corresponding to the search result set and decrypting using the corresponding symmetric key includes:

Decrypt the search results in the search result set according to the first key, and obtain a file identifier and a symmetric encryption key;

Send the file identifier to the cloud server to obtain the first file ciphertext returned by the cloud server, and use the corresponding symmetric key to extract the file corresponding to the first file ciphertext.
An electronic device comprising: a memory, a processor, and a computer program stored on the memory and capable of running on the processor, characterized in that when the processor executes the computer program, claim 1 is realized The method according to any one of 8.
A computer-readable storage medium on which a computer program is stored, characterized in that when the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.