WO2018165835A1

WO2018165835A1 - Cloud ciphertext access control method and system

Info

Publication number: WO2018165835A1
Application number: PCT/CN2017/076545
Authority: WO
Inventors: 刘宏伟; 朱平; 张鹏; 陈泽虹
Original assignee: 深圳大学
Priority date: 2017-03-14
Filing date: 2017-03-14
Publication date: 2018-09-20

Abstract

Disclosed in the present invention are a cloud ciphertext access control method and system, the method comprising: when a user makes a request to a cloud server by means of an access end to access an encrypted file, the cloud server acquires a key cipher text corresponding to the file and determines whether the attributes of the user satisfy an access tree structure in the key cipher text; if yes, the cloud server makes a request to the access end to acquire a local key in a transformation key, decrypts the key cipher text according to the local key to obtain an intermediate cipher text, and sends the intermediate cipher text and a file cipher text corresponding to the file to the access end; and the access end receives the intermediate cipher text, decrypts the intermediate cipher text according to a stored private key to obtain a plaintext key, and decrypts the file cipher text according to the plaintext key so as to obtain the file. Thus, the security of data is ensured. Moreover, the cloud server undertakes part of decryption operation, and the decryption speed and efficiency are improved.

Description

Cloud ciphertext access control method and system

Technical field

The invention belongs to the field of cloud computing, and in particular relates to a cloud ciphertext access control method and device.

Background technique

Cloud computing links a large number of storage, computing, and software resources to provide computing, storage, and application services to users. Because cloud computing has a large amount of resources and is open, it often becomes the focus of hacker attacks. Therefore, the threat of security is a severe test for cloud computing.

Due to the separation of the data owner from the physical owner, the cloud computing and the user are in two different security domains, and the user is worried that the data stored on the cloud server is illegally accessed, lost, tampered with or forged. Therefore, the data uploaded by the user to the cloud server is stored in the cipher text on the cloud server, thereby preventing illegal access of data. However, the encryption and decryption of the existing ciphertext are very complicated. When the user requests access to the encrypted data through the terminal, a large amount of decryption operations are required to acquire the data, which results in occupying a large amount of memory resources in the terminal, thereby causing slow decryption. ,low efficiency.

Summary of the invention

The present invention provides a cloud ciphertext access control method and system, which aims to solve the problem of occupying a large amount of memory resources of the terminal due to a large number of decryption operations generated during the decryption process, thereby causing slow decoding speed and low efficiency.

The invention provides a cloud ciphertext access control method, comprising:

When the user requests access to the encrypted file from the cloud server, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree structure in the key ciphertext. If yes, requesting, by the accessing end, a local key in the conversion key, and decrypting the key ciphertext according to the local key, to decrypt the intermediate ciphertext, and the intermediate ciphertext and Transmitting a file ciphertext corresponding to the file to the access terminal;

Receiving, by the accessing end, the intermediate ciphertext, decrypting the intermediate ciphertext according to the stored private key, decrypting the plaintext key, and decrypting the ciphertext according to the plaintext key, To decrypt the file.

The present invention provides a cloud ciphertext access control system, including: a cloud server and an access terminal;

The cloud server is configured to: when the user requests access to the encrypted file from the cloud server, the user obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user meets the key ciphertext. Access tree structure, if yes, requesting the access terminal to obtain a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, The intermediate ciphertext and the file ciphertext corresponding to the file are forwarded to the access end;

The access end is configured to receive the intermediate ciphertext, and use the stored private key to the intermediate cipher The text is decrypted to decrypt the plaintext key, and the file ciphertext is decrypted according to the plaintext key to decrypt the file.

The cloud ciphertext access control method and system provided by the present invention, when the user requests access to the encrypted file from the cloud server through the access terminal, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the The access tree structure in the key ciphertext, if yes, requesting the access terminal to obtain the local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, The intermediate ciphertext and the file ciphertext corresponding to the file are forwarded to the access terminal, and the access terminal receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and Decrypting the ciphertext according to the plaintext key to decrypt the file, so that only the privileged user can decrypt the file, ensuring the security of the data, and the cloud server decrypts the ciphertext according to the local key. Undertake part of the decryption operation, reduce the amount of decryption operations on the access side, improve the decryption speed and efficiency, thereby increasing the speed at which the access end accesses the encrypted file. .

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is some embodiments of the invention.

1 is a schematic flowchart of an implementation process of a cloud ciphertext access control method according to first and second embodiments of the present invention;

2 is a schematic structural diagram of a cloud ciphertext access control system according to a third embodiment of the present invention;

3 is a schematic structural diagram of a cloud ciphertext access control system according to a fourth embodiment of the present invention;

4 is a schematic diagram of four physical devices in a cloud ciphertext access control system according to an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The embodiments are merely a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Referring to FIG. 1 , FIG. 1 is a schematic flowchart of an implementation process of a cloud ciphertext access control method according to a first embodiment of the present invention. The cloud ciphertext access control method shown in FIG. 1 mainly includes the following steps:

S101. When the user requests access to the encrypted file from the cloud server by using the access terminal, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree structure in the key ciphertext, and if so, And requesting, by the access terminal, the local key in the conversion key, and decrypting the key ciphertext according to the local key, to decrypt the intermediate ciphertext, and encrypting the intermediate ciphertext and the file corresponding to the file The text is forwarded to the access terminal.

The user is a data visitor who needs to access the encrypted file from the cloud server. The user sends an access request to the cloud server by using the access terminal, where the access terminal can be a computer, a mobile phone, a smart TV, a tablet computer, etc., which supports interaction with the cloud server and can read data.

The encrypted file is encrypted and stored on the cloud server. The user's attribute is used to divide users who access different levels of encrypted files. For example, a level of three encrypted files is available: low-level, intermediate, and advanced. If the attribute of the user is attribute A, the user of attribute A can access advanced. The encrypted file; if the attribute of the user is attribute B, the user of attribute B can access the intermediate encrypted file; if the attribute of the user is attribute C, the user of attribute C can access the encrypted file of the lower level. Each attribute can correspond to one level or multiple levels. The access tree structure is a data access structure. The cloud server determines whether the user has the right to access the file by determining whether the attribute of the user satisfies the level in the access tree structure.

The key ciphertext is the ciphertext of the key that encrypts the file. The local key is a part of the key of the conversion key, and the local key is uploaded by the user to the cloud server, and the cloud server decrypts the key ciphertext according to the local key, and only the intermediate ciphertext can be decrypted. The file cannot be decrypted directly, which can effectively ensure the security of the data. At the same time, the cloud server undertakes part of the decryption operation, which improves the decryption speed and efficiency.

S102. The access end receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and decrypt the ciphertext according to the plaintext key to decrypt the ciphertext. The document.

The plaintext key is a decryption key corresponding to the key that encrypts the file.

In the embodiment of the present invention, when the user requests access to the encrypted file from the cloud server, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree in the key ciphertext. Structure, if yes, requesting the access terminal to obtain a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, the intermediate ciphertext and the file The corresponding file ciphertext is forwarded to the access terminal, and the access terminal receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and according to the plaintext key The file ciphertext is decrypted to decrypt the file, so that only the user with authority can decrypt the file, ensuring the security of the data, and the cloud server decrypts the ciphertext according to the local key, and undertakes part of the decryption operation. , reducing the amount of decryption operations on the access side, improving the decryption speed and efficiency, thereby increasing the speed at which the access end accesses the encrypted file.

Referring to FIG. 1 , a cloud ciphertext access control method provided by a second embodiment of the present invention mainly includes the following steps:

The encrypted file is encrypted and stored on the cloud server. The user's attributes are used to divide users who access different levels of encrypted files, for example, to have a level of three encrypted files: Low-level, intermediate, and advanced. If the attribute of the user is attribute A, the user of attribute A can access the advanced encrypted file; if the attribute of the user is attribute B, the user of attribute B can access the intermediate encrypted file; The attribute is attribute C, and the user of attribute C can access the low-level encrypted file. Each attribute can correspond to one level or multiple levels. The access tree structure is a data access structure. The cloud server determines whether the user has the right to access the file by determining whether the attribute of the user satisfies the level in the access tree structure. If the attribute of the user does not satisfy the access tree structure in the key ciphertext, the user will not be able to access the file, that is, the user does not have permission to access.

Further, when the user requests access to the encrypted file from the cloud server by using the access terminal, the cloud server obtains the key ciphertext corresponding to the file, specifically:

The Key Authority (KA, Key Authority) constructs a bilinear group G ₀ whose selection order is a prime number p, and a generator element is g;

Defining a global attribute set L = (a ₁ , a ₂ , ..., a _m } and a security level k, where j belongs to 1 to m;

Selecting the random number v _j ∈Z _p and using the random number v _j as the attribute version key VK _j =v _j , and generating the sub public key according to the attribute version key

Where Z _p is a finite field;

Two random numbers α, β∈Z _{p are selected} , and according to the two random numbers α, β, the sub-public key and the bilinear group respectively generate a system main private key

And system master public key

Suppose the system has m attributes L = (a ₁ , a ₂ , ..., a _m }. Let G ₀ be a bilinear group with a prime p, g is a generator of G ₀ , e: G ₀ × G ₀ → G _T represents a bilinear map. The hash function H: {0, 1} ^* → G _{0 ,} where each attribute in L corresponds to an attribute version key.

After the system is initialized, the key authority sets a user attribute set S for each user, where S is a subset of L;

Two random numbers r, z ∈ Z _{p are selected} . According to the two random numbers r, z, the system main private key and the user attribute set S respectively generate the conversion key TK={D=g ^{(α+r ) / β} ,

And the private key SK = (z, TK).

The data owner (DO, data owner) encrypts the file according to the preset application key ck by a symmetric encryption algorithm to generate the file ciphertext E _ck (M), where M represents the file;

Selecting a polynomial q _x for each node x in the access tree structure T;

Each set of the polynomial corresponding to the node x Q _x D _x corresponds to _the order of the nodes than the threshold value K _x at least 1, where k _{_x} = d _x +1;

From the root node R, select the random number s∈Z _p , and set q _R (0)=s, and select d _R nodes to define the polynomial q _R ;

Set q _x (0)=q _partent(x) (index(x)) for each non-root node x and select d _x nodes to define the polynomial q _x .

The application key ck is encrypted by the access tree structure T and the system main public key to obtain the key ciphertext CT, wherein the key ciphertext CT is:

Where X is a set of attributes corresponding to leaf nodes in the access tree structure T;

The key ciphertext CT and the file ciphertext are uploaded to the cloud server.

The symmetric encryption algorithm refers to an encryption algorithm that uses the same key for the encryption process and the decryption process, that is, the encryption key can be derived from the decryption key, and the decryption key can also be derived from the encryption key. Therefore, the application key is the same as the plaintext key.

Further, requesting the access terminal to obtain the local key in the conversion key, and decrypting the key ciphertext according to the local key, to decrypt the intermediate ciphertext is specifically:

Receiving, by the cloud server, a local key in the conversion key sent by the access terminal, where the local key in the conversion key

Pre-define the recursive operation DecryptNode(CT, TK', x), wherein if node x is a leaf node in the access tree structure T, let a _j =att(x) and a _j ∈S, then

If x is not a leaf node in the access tree structure T, and all child nodes n in the node x are set, F _n =DecryptNode(CT, TK', n), then

Where j=index(n), S _x '={index(n):n∈S _x };

Calculating the intermediate ciphertext T={A, B} by performing a function of the function DecryptNode (CT, TK', R) corresponding to the root node R in the access tree structure T, where

F _R =DecryptNode(CT,TK',R)

Let A=F _R =e(g,g) ^rs/z ,

Then, the intermediate ciphertext is decrypted according to the stored private key to decrypt the plaintext key, and the ciphertext of the file is decrypted according to the plaintext key, so as to decrypt the file as follows:

The access terminal decrypts the plaintext key ck according to the private key SK and the received intermediate ciphertext T={A, B}, wherein

The access terminal decrypts the file ciphertext E _ck (M) by the plaintext key ck to decrypt the file M.

If the node x is a leaf node in the access tree structure T, and

Then DecryptNode(CT, TK, x) = ⊥.

If x is not a leaf node in the access tree structure T, and S _x is a set of arbitrary k _x child nodes n, then F _n ≠⊥, if the set does not exist, F _n = ⊥.

The private key SK is pre-delivered to each user by the key authority according to the attributes of the user.

Further, the method further includes:

When the attribute x' of the undo user μ is revoked, the key authority selects the random number v _x' ^* ∈Z _p (v _x' ^* ≠v _x' ) and attributes the attribute version key corresponding to the attribute x' VK _x' =v _{x' is} replaced with the attribute version key VK _x' ^* , VK _x' ^* = v _x' ^* , and the update key is generated according to VK _x' ^* is UK _x' , according to the replaced attribute version Key VK _x' ^* update the system's master public key to

And sending the update key UK _x' to the access end of each non-revoked user and the cloud server, wherein

The access end of each non-revoked user receives the update key UK _x' sent by the key authority, and the access end of each non-revoked user updates the stored private key SK to:

The cloud server receives the update key UK _x' sent by the key authority and updates the key ciphertext CT to:

The above key update process includes three parts: one is that the key authority generates an update key; the other is that the non-revoked user updates the private key stored by itself; and the third is that the cloud server updates the ciphertext.

It should be noted that the key authority, the non-revoked user, and the cloud server are only updated with the genus. The sex x' has an associated key and ciphertext, so that the update occupies less resources, and when the user identity changes, the key and ciphertext can also be updated in time to ensure data security.

In the embodiment of the present invention, when the user requests access to the encrypted file from the cloud server, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree in the key ciphertext. Structure, if yes, requesting the access terminal to obtain a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, the intermediate ciphertext and the file The corresponding file ciphertext is forwarded to the access terminal, and the access terminal receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and according to the plaintext key The file ciphertext is decrypted to decrypt the file, and when a user is revoked, the key authority, the access end, and the cloud server update the key or ciphertext, so that only the authorized user can decrypt the file, ensuring that the file is secured. The security of the data, at the same time, the cloud server decrypts the ciphertext according to the local key, and undertakes part of the decryption operation, reducing the amount of decryption operation of the access end. Decryption high speed and efficiency, thereby increasing the speed of the access terminal to access encrypted files.

Referring to FIG. 2, FIG. 2 is a schematic structural diagram of a cloud ciphertext access control system according to a third embodiment of the present invention. For convenience of description, only parts related to the embodiment of the present invention are shown. The cloud ciphertext access control system illustrated in FIG. 2 may be the execution body of the cloud ciphertext access control method provided by the foregoing embodiment shown in FIG. The cloud ciphertext access control system illustrated in FIG. 2 mainly includes: a cloud server 201 and an access terminal 202. The above functional modules are described in detail as follows:

The cloud server 201 is configured to: when the user requests access to the encrypted file from the cloud server 201, the user obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree in the key ciphertext. Structure, if yes, requesting the access terminal 202 to acquire a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, the intermediate ciphertext and the The file ciphertext corresponding to the file is forwarded to the access terminal 202.

The user is a data visitor who needs to access the encrypted file from the cloud server 201. The user sends an access request to the cloud server 201 by using the access terminal 202. The access terminal 202 can be a terminal that supports data exchange with the cloud server, such as a computer, a mobile phone, a smart TV, a tablet computer, and the like.

The encrypted file is data that is encrypted and stored on the cloud server 201. The user's attribute is used to divide users who access different levels of encrypted files. For example, a level of three encrypted files is available: low-level, intermediate, and advanced. If the attribute of the user is attribute A, the user of attribute A can access advanced. The encrypted file; if the attribute of the user is attribute B, the user of attribute B can access the intermediate encrypted file; if the attribute of the user is attribute C, the user of attribute C can access the encrypted file of the lower level. Each attribute can correspond to one level or multiple levels. The access tree structure is a data access structure. The cloud server 201 determines whether the user has the right to access the file by determining whether the attribute of the user satisfies the level in the access tree structure.

The key ciphertext is the ciphertext of the key that encrypts the file. The local key is a part of the key of the conversion key. The cloud server 201 decrypts the key ciphertext according to the local key, and can only decrypt the intermediate ciphertext, and cannot directly decrypt the file, thereby effectively ensuring the data. The security, while the cloud server undertakes part of the decryption operation, improving the decryption speed and efficiency.

The access end 202 is configured to receive the intermediate ciphertext and use the stored private key to the intermediate ciphertext Decrypting to decrypt the plaintext key and decrypting the ciphertext according to the plaintext key to decrypt the file.

For details of the embodiment, please refer to the description of the embodiment shown in FIG. 1 , and details are not described herein again.

In the embodiment of the present invention, when the user requests the cloud server 201 to access the encrypted file through the access terminal, the cloud server 201 obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the key ciphertext. Accessing the tree structure, if yes, requesting the access terminal 202 to acquire the local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, and the intermediate ciphertext The file ciphertext corresponding to the file is forwarded to the access terminal 202, and the access terminal 202 receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and according to the The plaintext key decrypts the ciphertext of the file to decrypt the file, so that only the user with authority can decrypt the file, ensuring the security of the data, and the cloud server decrypts the ciphertext according to the local key. Part of the decryption operation reduces the amount of decryption operations on the access side, improves the decryption speed and efficiency, and increases the speed at which the access end accesses the encrypted file.

Referring to FIG. 3, FIG. 3 is a schematic structural diagram of a cloud ciphertext access control system according to a fourth embodiment of the present invention. For convenience of description, only parts related to the embodiment of the present invention are shown. The cloud ciphertext access control system illustrated in FIG. 3 may be the execution body of the cloud ciphertext access control method provided by the foregoing embodiment shown in FIG. The cloud ciphertext access control system illustrated in FIG. 3 mainly includes: a key authority 301, a data owner 302, a cloud server 303, and an access terminal 304. The above functional modules are described in detail as follows:

The key authority 301 is used to perform the following steps:

Constructing a selection order of prime p, and generating a bilinear group G _{0 of} elements g;

Where Z _p is a finite field;

Two random numbers α, β∈Z _{p are selected} , and according to the two random numbers α, β, the sub-public key and the bilinear group respectively generate the system main private key MSK={β, g ^α , {MSK _j =VK _j |a _j ∈L}}, and the system master public key

Setting a user attribute set S for each user, where S is a subset of L;

And the private key SK = (z, TK).

Further, the data owner 302 is configured to perform the following steps:

The file is encrypted according to a preset application key ck and encrypted by a symmetric encryption algorithm to generate the file ciphertext E _ck (M), where M represents the file;

Selecting a polynomial q _x for each node x in the access tree structure T;

The key ciphertext CT and the file ciphertext are uploaded to the cloud server 303.

The cloud server 303 is configured to: when the user requests the cloud server 303 to access the encrypted file through the accessing end 304, obtain the key ciphertext corresponding to the file, and determine whether the attribute of the user satisfies the access tree in the key ciphertext. Structure, if yes, requesting the access terminal 304 to obtain a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, the intermediate ciphertext and the The file ciphertext corresponding to the file is forwarded to the access terminal 304.

Further, the cloud server 303 is further configured to perform the following steps:

Receiving a local key in the conversion key sent by the access terminal 304, wherein the local key in the conversion key

Where j=index(n), S _x '={index(n):n∈S _x };

Calculating the intermediate ciphertext T={A, B} by calculating a function DecryptNode(CT, TK', R) corresponding to the root node R in the access tree structure T, wherein

Let A=F _R =e(g,g) ^rs/z ,

The accessing end 304 is configured to receive the intermediate ciphertext, and decrypt the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and decrypt the ciphertext according to the plaintext key. Decrypt the file.

Further, the accessing end 304 is further configured to decrypt the plaintext key ck according to the private key SK and the received intermediate ciphertext T={A, B}, where

The access terminal 304 is further configured to decrypt the file ciphertext E _ck (M) by using the plaintext key ck to decrypt the file M.

The key authority 301 is further configured to: when the attribute x' of the undo user μ is revoked, select a random number v _x′ ^* ∈Z _p (v _x′ ^* ≠v _x′ ), and corresponding the attribute x′ The attribute version key VK _x' = v _{x ' is} replaced with the attribute version key VK _x' ^* , VK _x' ^* = v _{x '} ^* , and the update key is generated according to VK _x' ^* is UK _x' , based on The replaced attribute version key VK ^* _x' updates the system master public key to

And sending the update key UK _x' to the access end 304 of each non-revoked user and the cloud server 303, where

The access end 304 of each non-revoked user is further configured to receive the update key UK _x' sent by the key authority 301, and the access end 304 of each non-revoked user updates the stored private key SK to:

The cloud server 303 is further configured to receive the update key UK _x' sent by the key authority 301, and update the key ciphertext CT to:

As shown in FIG. 4, FIG. 4 is a schematic diagram of four physical devices in a cloud ciphertext access control system.

In the embodiment of the present invention, when the user requests the cloud server 303 to access the encrypted file through the accessing end 304, the cloud server 303 obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the key ciphertext. The access tree structure, if yes, requesting the access terminal 304 to obtain the local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, and the intermediate secret And the file ciphertext corresponding to the file is forwarded to the accessing end 304, the accessing end 304 receives the intermediate ciphertext, and decrypts the intermediate ciphertext according to the stored private key to decrypt the The plaintext key, and decrypting the ciphertext according to the plaintext key, to decrypt the file, so that only the user with authority can decrypt the file, ensuring the security of the data, and the cloud server is based on the local key pair. The ciphertext performs the decryption operation, undertakes part of the decryption operation, reduces the decryption operation amount of the access end, improves the decryption speed and efficiency, and increases the speed at which the access end accesses the encrypted file.

In the various embodiments provided herein, it should be understood that the disclosed systems, devices, and methods may be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be another division manner, for example, multiple modules or components may be combined or Can be integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication link shown or discussed may be an indirect coupling or communication link through some interface, device or module, and may be electrical, mechanical or otherwise.

The modules described as separate components may or may not be physically separated. The components displayed as modules may or may not be physical modules, that is, may be located in one place, or may be distributed to multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the 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 physically separately, or two or more modules may be integrated into one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

The integrated modules, if implemented in the form of software functional modules and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention, which is essential or contributes to the prior art, or all or part of the technical solution, may be embodied in the form of a software product stored in a storage medium. A number of instructions are included to cause 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 foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, which can store program codes.

It should be noted that, for the foregoing method embodiments, for the sake of brevity, they are all described as a series of action combinations, but those skilled in the art should understand that the present invention is not limited by the described action sequence. Because certain steps may be performed in other sequences or concurrently in accordance with the present invention. In the following, those skilled in the art should also understand 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 descriptions of the various embodiments are all focused, and the parts that are not detailed in a certain embodiment can be referred to the related descriptions of other embodiments.

The above is a description of the cloud ciphertext access control method and system provided by the present invention. For those skilled in the art, according to the idea of the embodiment of the present invention, there will be changes in specific implementation modes and application scopes. The contents of this specification are not to be construed as limiting the invention.

Claims

A cloud ciphertext access control method, comprising:

When the user requests access to the encrypted file from the cloud server, the cloud server obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user satisfies the access tree structure in the key ciphertext. If yes, requesting, by the accessing end, a local key in the conversion key, and decrypting the key ciphertext according to the local key, to decrypt the intermediate ciphertext, and the intermediate ciphertext and Transmitting a file ciphertext corresponding to the file to the access terminal;

Receiving, by the accessing end, the intermediate ciphertext, decrypting the intermediate ciphertext according to the stored private key, decrypting the plaintext key, and decrypting the ciphertext according to the plaintext key, To decrypt the file.
The method according to claim 1, wherein when the user requests access to the encrypted file from the cloud server by using the access terminal, the cloud server further includes:

The key authority constructs a selection order of prime p, and a bilinear group G 0 whose generator is g;

Defining a global attribute set L={a 1 , a 2 , . . . , a m } and a security level k;

Selecting a random number v j ∈Z p , and using the random number v j as an attribute version key VK j =v j , and generating a sub-public key according to the attribute version key
Where Z p is a finite field;

Two random numbers α, β∈Z p are selected , and according to the two random numbers α, β, the sub-public key and the bilinear group, respectively generate a system master private key MSK={β, g α , {MSK j =VK j |a j ∈L}}, and the system master public key

Setting a user attribute set S for each user, where S is a subset of L;

Selecting two random numbers r, z ∈ Z p , respectively, according to the two random numbers r, z, the system master private key and the user attribute set S, respectively generating the conversion key
And the private key SK = (z, TK).
The method according to claim 2, wherein when the user requests access to the encrypted file from the cloud server through the access end, the cloud server further includes:

The data owner encrypts the file according to a preset application key ck and generates a file ciphertext E ck (M) by using a symmetric encryption algorithm, where M represents the file;

Selecting a polynomial q x for each node x in the access tree structure T;

X provided corresponding to each of the nodes in order polynomial Q x D x ratio of each node corresponding to the threshold value K x at least 1, where k x = d x +1;

From the root node R, select the random number s∈Z p , and set q R (0)=s, and select d R nodes to define the polynomial q R ;

Set q x (0)=q partent(x) (index(x)) for each non-root node x and select d x nodes to define the polynomial q x .

Encrypting the application key ck by using the access tree structure T and the system master public key Go to the key ciphertext CT, wherein the key ciphertext CT is:

Where X is a set of attributes corresponding to leaf nodes in the access tree structure T;

Uploading the key ciphertext CT and the file ciphertext to the cloud server.
The method according to claim 3, wherein the requesting to the access terminal to acquire a local key in a conversion key, and decrypting the key ciphertext according to the local key to decrypt The intermediate ciphertext includes:

Receiving, by the cloud server, a local key in the conversion key sent by the access terminal, where the local key in the conversion key

Pre-defining the recursive operation Decrypt Node (CT, TK', x), wherein if the node x is a leaf node in the access tree structure T, let a j =att(x) and a j ∈S, then

If x is not a leaf node in the access tree structure T and is all child nodes n in the node x, setting F n =DecryptNode(CT, TK', n), then

Where j=index(n), S x '={index(n):n∈S x };

Calculating the intermediate ciphertext T={A, B} by performing a function of the function DecryptNode (CT, TK', R) corresponding to the root node R in the access tree structure T, where

Let A=F R =e(g,g) rs/z ,

Then, the intermediate ciphertext is decrypted according to the stored private key to decrypt the plaintext key, and the ciphertext is decrypted according to the plaintext key, to decrypt the file, including:

The access end decrypts according to the private key SK and the received intermediate ciphertext T={A, B}

The plaintext key ck, wherein

The access terminal decrypts the file ciphertext E ck (M) by using the plaintext key ck to decrypt the file M.
The method of claim 4, wherein the method further comprises:

When the attribute x' of the revoked user μ is revoked, the key authority selects the random number v x' * ∈Z p (v x' * ≠v x' ) and attributes the attribute corresponding to the attribute x' The key VK x' = v x ' is replaced with the attribute version key VK x' * , VK x' * = v x ' * , and the update key generated according to VK * x' is UK x' , according to the replacement The attribute version key VK x' * updates the system master public key to
And sending the update key UK x' to the access end of each non-revoked user and the cloud server, where

The access end of each non-revoked user receives the update key UK x' sent by the key authority, and the access end of each non-revoked user updates the stored private key to:

Receiving, by the cloud server, the update key UK x' sent by the key authority, and updating the key ciphertext to:
A cloud ciphertext access control system, comprising: a cloud server and an access terminal;

The cloud server is configured to: when the user requests access to the encrypted file from the cloud server, the user obtains the key ciphertext corresponding to the file, and determines whether the attribute of the user meets the key ciphertext. Access tree structure, if yes, requesting the access terminal to obtain a local key in the conversion key, and decrypting the key ciphertext according to the local key to decrypt the intermediate ciphertext, The intermediate ciphertext and the file ciphertext corresponding to the file are forwarded to the access end;

The access end is configured to receive the intermediate ciphertext, and decrypt the intermediate ciphertext according to the stored private key to decrypt the plaintext key, and pair the ciphertext according to the plaintext key Decryption is performed to decrypt the file.
The apparatus according to claim 5, wherein said system further comprises: a key authority;

The key authority is configured to perform the following steps:

Constructing a selection order of prime p, and generating a bilinear group G 0 of g;

Defining a global attribute set L={a 1 , a 2 , . . . , a m } and a security level k;

Selecting a random number v j ∈Z p , and using the random number v j as the attribute version key VK j =v j , and generating a sub-public key according to the attribute version key
Where Z p is a finite field;

Selecting two random numbers α, β∈Z p , and generating a system master private key MSK={β according to the two random numbers α, β∈Z p , the sub-public key and the bilinear group respectively , g α , {MSK j =VK j |a j ∈L}}, and the system master public key

Setting a user attribute set S for each user, where S is a subset of L;

Selecting two random numbers r, z ∈ Z p , respectively, according to the two random numbers r, z, the system master private key and the user attribute set S, respectively generating the conversion key
And the private key SK = (z, TK).
The apparatus according to claim 7, wherein said system further comprises: a data owner;

The data is the master and is used to perform the following steps:

Generating the file ciphertext E ck (M) according to a preset application key ck and encrypting the file by a symmetric encryption algorithm, where M represents the file;

Selecting a polynomial q x for each node x in the access tree structure T;

X provided corresponding to each of the nodes in order polynomial Q x D x ratio of each node corresponding to the threshold value K x at least 1, where k x = d x +1;

From the root node R, select the random number s∈Z p , and set q R (0)=s, and select d R nodes to define the polynomial q R ;

Set q x (0)=q partent(x) (index(x)) for each non-root node x and select d x nodes to define the polynomial q x .

Encrypting the application key ck by using the access tree structure T and the system master public key to obtain the key ciphertext CT, wherein the key ciphertext CT is:

Where X is a set of attributes corresponding to leaf nodes in the access tree structure T;

Uploading the key ciphertext CT and the file ciphertext to the cloud server.
The device of claim 8 wherein:

The cloud server is further configured to perform the following steps:

Receiving a local key in the conversion key sent by the access terminal, where the local key in the conversion key

Recursive operation DecryptNode(CT, TK', x) is defined in which, if node x is a leaf node in the access tree structure T, let a j =att(x) and a j ∈S, then

If x is not a leaf node in the access tree structure T and is all child nodes n in the node x, setting F n =DecryptNode(CT, TK', n), then

Where j=index(n), S x '={index(n):n∈S x };

Calculating the intermediate ciphertext T={A, B} by performing a function of the function DecryptNode (CT, TK', R) corresponding to the root node R in the access tree structure T, where

Let A=F R =e(g,g) rs/z ,

The accessing end is further configured to decrypt the plaintext key ck according to the private key SK and the received intermediate ciphertext T={A, B}, where
And decrypting the file ciphertext E ck (M) by the plaintext key ck to decrypt the file M.
The device of claim 9 wherein:

The key authority is further configured to: when the attribute x' of the undo user μ is revoked, select a random number v x′ * ∈Z p (v x′ * ≠v x′ ), and the attribute x′ The corresponding attribute version key VK x' = v x ' is replaced with the attribute version key VK x' * , VK x' * = v x ' * , and the update key is generated for UK x' according to VK x' * , Updating the system master public key according to the replaced attribute version key VK x' *
And sending the update key UK x' to the access end of each non-revoked user and the cloud server, where

The access terminal is further configured to receive the update key UK x′ sent by the key authority, and update the stored private key to:

The cloud server is further configured to receive the update key UK x′ sent by the key authority, and update the key ciphertext to: