CN111526155B - System for protecting user privacy in social network and optimal path matching method - Google Patents
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Abstract
The invention relates to a system for protecting user privacy in a social network and an optimal path matching method. The method comprises the following steps: the trusted center generates system parameters and a secret key and sends the system parameters to the server and the user; the user registers; the server registers; a user constructs vertex information and weight information and sends ciphertext information generated in the process of constructing the vertex information and the weight information to a server; the server is used for constructing a social graph according to the vertex information and the weight information; a query user in the users uploads a starting terminal mark to a server; the server generates a path sequence and a weight sequence according to the social graph and the starting and ending point identification; the server sends the weight sequence to the inquiry user so that the inquiry user can determine the position of the ciphertext; and the inquiry user determines the optimal path from the path sequence by adopting an inadvertent transmission mode according to the ciphertext position. The method and the device can ensure that the privacy of the user is not revealed during path query, and have the advantages of high query speed, accurate and efficient processing.
Description
Technical Field
The invention relates to the technical field of social networks, in particular to a system for protecting user privacy in a social network and an optimal path matching method.
Background
In order to realize various intelligent services, such as recommendation service, sharing service, and query service, the online social network needs to perform information association query and matching by using personal attribute information of a user to obtain optimal recommendations in the social network. However, the user attribute information includes personal privacy of many users, such as sensitive information of user age, gender, work units, place of residence, and the like. Malicious attackers can obtain, analyze and use the data for illegal operations by means of snooping and the like. Therefore, how to protect the privacy of users in social networks is an important issue.
In the social network, all users upload their private information to a cloud server. The user provides the source point information and the end point information, so that the propagation path between the two coordinates can be inquired, wherein the optimal propagation path represents that the propagation cost of the user is smaller and the propagation is more effective. Through the optimal propagation path, the user can rapidly and efficiently propagate a certain message to the target user. In order to protect privacy, user information is usually uploaded after being encrypted, and propagation cost (defined as weight value) between users needs to be compared in an outsourcing environment. The whole process should ensure that the server cannot know the sensitive data of the user and the system user can not obtain any information except for the propagation path. Some methods for solving the above problems, such as a path query method based on a homomorphic encryption algorithm, also appear; the homomorphism property enables the ciphertext obtained by encrypting to be subjected to certain operation to be equal to the ciphertext obtained by performing another operation on the encrypted plaintext. However, in the existing path query scheme, firstly, the definition of weight information between vertexes is not accurate enough, the interaction between the vertexes is not considered, and the purpose of path query cannot be clearly expressed; secondly, the query speed is positively correlated with the number of vertexes, so that the practicability of query of a large social network cannot be ensured or the balance between accuracy and efficiency needs to be made.
Disclosure of Invention
The invention aims to provide a system for protecting user privacy in a social network and an optimal path matching method, which can ensure that propagation paths of any two vertexes of a large-scale social network can be quickly inquired, the inquiry speed does not depend on the number of users, and the privacy protection safety is improved.
In order to achieve the purpose, the invention provides the following scheme:
a system for protecting user privacy in a social network, comprising: the system comprises a trusted center, a server and a user, wherein the trusted center is used for generating system parameters and a secret key and sending the parameters to the server; the method comprises the steps that after the user registers, vertex information and weight information are constructed, ciphertext information generated in the process of constructing the vertex information and the weight information is sent to a server, the server is used for constructing a social graph according to the vertex information and the weight information after registering, a query user in the user is used for providing identification marks of the user and a target user, the server is used for querying all propagation paths and corresponding weights, and an optimal path is provided for the query user through an inadvertent transmission mode.
An optimal path matching method for protecting user privacy in a social network comprises the following steps:
the trusted center generates system parameters and a secret key and sends the system parameters to the server and the user;
the user registers;
the server registers;
the user constructs vertex information and weight information and sends ciphertext information generated in the process of constructing the vertex information and the weight information to the server;
the server is used for constructing a social graph according to the vertex information and the weight information;
a query user in the users uploads a starting end point identifier to the server;
the server generates a path sequence and a weight sequence according to the social graph and the starting and ending point identification;
the server sends the weight value sequence to the inquiry user so that the inquiry user can determine the ciphertext position;
and the inquiry user determines an optimal path from the path sequence by adopting an inadvertent transmission mode according to the ciphertext position.
Optionally, the trusted center generates system parameters and a secret key, and sends the system parameters to the server and the user, which specifically includes:
acquiring a safety parameter kappa;
calculating a master public key mpk and a master key msk of the encryption algorithm according to the security parameters, wherein mpk is (g) msk ,g,p)，
p is a large prime number and satisfies | p | ═ k,
is [1, p-1 ]]In an arbitrary integer, g is
A generator of (2); selecting a random number R, wherein | R | < | p |/3;
obtaining a key pair (sk) 1 ,sk 2 ) The key pair includes a first key sk 1 And a second key sk 2 Wherein, in the step (A),
sk 1 +sk 2 ＝mskmod(p-1)；
randomly acquiring n user key vectors
Wherein the content of the first and second substances,
and issuing parameter information, wherein the parameter information comprises the master public key, the generator, the prime number and the random number.
Optionally, the registering of the user specifically includes:
sending a first registration request;
the trusted center follows the integer sequence according to the first registration requestRandomly selecting an integer as the ID of the current user i And combining the key vector
Returning to the current user;
sending the identification ID to all users connected with the current user i ；
The inquiring user obtains the ID i Then sending a second registration request;
the trusted center returns the first key sk to the inquiring user according to the second registration request 1 。
Optionally, the registering by the server specifically includes:
sending a third registration request;
the trusted center returns the second key sk to the server according to the third registration request 2 。
Optionally, the user constructs vertex information and weight information, and sends ciphertext information generated in the process of constructing the vertex information and the weight information to the server, and the method specifically includes:
obtaining the USER i Attribute information of (2);
binarizing the attribute information through one-hot coding to enable the value of only one bit in a binary value corresponding to each dimension attribute to be 1; the current USER USER i Capable of converting all discrete attributes of an individual into an attribute vector of length l
The USER USER i According to the key vector
Encrypting the attribute vector
Obtaining social network informationVertex information v in (1) i ；
USER for each connected USER j The current USER USER i Sending an application to the trusted center;
the trusted center returns a weight key according to the application;
calculating a weight ciphertext by using the encryption homomorphism property and the weight key, and sending the weight ciphertext to a server;
and the server integrates the ciphertext to obtain weight information.
Optionally, the server generates a path sequence and a weight sequence according to the social graph and the start and end point identifier, and specifically includes:
determining a vertex v corresponding to a starting point identifier in the social graph s And is defined as a first layer set of starting vertices S 1 (ii) a Finding the vertex v corresponding to the terminal point identification t And defined as a first layer termination vertex set T 1 ；
Determining the first layer starting vertex set S 1 And the first layer termination vertex set T 1 Is denoted by v u Wherein v is u ∈{S 1 ∩T 1 Querying a vertex v according to the social graph s And v u And v u And v t The weights between them are respectively marked as E s,u And E u,t D, E is to s,u ·E u,t Added to the weight sequence
In, query vertex v simultaneously u Corresponding identity ID u Will ID u Join to Path sequence
Performing the following steps;
determining the first set of starting vertices S from the social graph 1 Each vertex v of i All connected vertices v of j And is defined as the second layer initial vertex set S 2 At the same time v i →v j Adding to a set of prepositioned vertices P 1 ；
Determining the second layer starting vertex set S 2 And the first layer termination vertex set T 1 Is updated by v u Wherein v is u ∈{S 2 ∩T 1 At the same time in the set of front vertices P 1 In finding v u And is denoted by v i Sequentially querying vertexes v according to the social graph s And v i 、v i And v u And v u And v t The weights between are respectively marked as E s,i 、E i,u And E u,t A 1 is mixing E s,i ·E i,u ·E u,t Added to the weight sequence
In, query vertex v simultaneously i And v u Corresponding identity ID i And ID u Will ID i ·R+ID u Join to Path sequences
Performing the following steps;
determining the first set of termination vertices T from the social graph 1 Each vertex v of i′ All connected vertices v of j′ And is defined as a second layer termination vertex set T 2 While v is being measured i′ →v j′ Adding to the post-vertex set P 2 ；
Determining the second layer starting vertex set S 2 And the second layer termination vertex set T 2 Is updated by v u Wherein v is u ∈{S 2 ∩T 2 At the same time in the set of front vertices P 1 In finding v u And is denoted by v i At said set of post-vertices P 2 In finding v u Is denoted by v i′ Sequentially querying vertexes v according to the social graph s And v i 、v i And v u 、v u And v i′ And v i′ And v u The weights between are respectively marked as E s,i 、E i,u 、E u,i′ And E i′,t A 1 is mixing E s,i ·E i,u ·E u,i′ ·E i′,t Is added to
In, query vertex v simultaneously i 、v i′ And v u Corresponding identity ID i 、ID i′ And ID u Will ID i ·R 2 +ID u ·R+ID i′ Is added to
In (3), get the path sequence
Sum weight sequence
Optionally, the sending, by the server, the weight sequence to the querying user so that the querying user determines a ciphertext position includes:
according to the second key sk 2 Decrypting the sequence of weights
Each element of (a) obtains a first sequence of decryption weights
And sending the information to the inquiry user;
the inquiring user is according to the first key sk 1 Decrypting the first weight sequence
Each element of (2) to obtain a second decryption weight sequence
According to the second decryption weight sequence
And obtaining the ciphertext position.
Optionally, the determining, by the querying user, an optimal path from the path sequence according to the ciphertext position in an oblivious transmission manner specifically includes:
the server sends q random integers C to the inquiring user h ，
Wherein q is a sequence of paths
The number of the elements in the Chinese character,
the querying user generates a key
Calculating q public keys and sending each public key to the server, wherein the public key corresponding to the ciphertext position is generated by a secret key k, and the rest public keys are generated according to the public key and the integer C h Generating;
the server checks each public key to obtain a check result;
the server encrypts a path sequence by using the public key according to the check result and sends the path sequence to the inquiry user;
and the inquiry user decrypts the path ciphertext corresponding to the ciphertext position in the path sequence according to the key k, and can determine the optimal path of the social network by an accidental transmission mode.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
(1) the invention has high security, and all processes are realized by using an ElGamal encryption system. Even if the server has complete graph information such as vertex information and weight information, the server and external attackers cannot obtain any private information as long as there is no collusion between the user and the server. Meanwhile, the user cannot recover the user key of the connected user from the weight key obtained by the vector inner product. Therefore, the invention has high privacy protection safety.
(2) By means of an inadvertent transmission mode, due to the fact that discrete logarithm is difficult to assume, the server does not know the specific content of the path which the user wants to query, namely the specific position of the ciphertext b cannot be judged; because the server verifies the correctness of the public key in transmission, the user can only obtain a path, namely, the key required by other ciphertexts can not be forged or judged except k.
(3) The invention provides an optimal path matching method for protecting user privacy in a social network, which is characterized in that on the premise of ensuring the security, by using a data structure of bidirectional breadth-first search of a source point and a destination point, the operation speed of a server is high, the processing is efficient, and parameters in the process can be pre-generated so as to reduce the actual operation time.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram illustrating a system for protecting user privacy in a social network according to the present invention;
FIG. 2 is a schematic diagram of internal data transmission of the system for protecting user privacy in the social network according to the present invention;
FIG. 3 is a flowchart of an optimal path matching method for protecting user privacy in a social network according to the present invention;
FIG. 4 is a flowchart of entity registration in a method according to an embodiment of the invention;
fig. 5 is a flow chart of an inadvertent transmission in a method according to an embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a system for protecting user privacy in a social network and an optimal path matching method, which can ensure that propagation paths of any two vertexes of a large social network can be quickly inquired, the inquiry speed does not depend on the number of users, and the privacy protection safety is improved.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
FIG. 1 is a diagram illustrating a system for protecting privacy of users in a social network according to the present invention. As shown in fig. 1, a system for protecting user privacy in a social network includes: trusted center 1, server 2, user 3. FIG. 2 is a schematic diagram of data transmission inside the system for protecting user privacy in the social network according to the present invention. As shown in fig. 2, the system includes a trusted center (TA), a server (CS) and a USER (USER). The trusted center 1 is used for generating system parameters and keys and sending the parameters to the server 2; the user 3 constructs vertex information and weight information after registration, ciphertext information generated in the process of constructing the vertex information and the weight information is sent to the server 2, the server 2 is used for constructing a social graph after registration according to the vertex information and the weight information, a query user in the user 3 is used for providing identification marks of the user and a target user, the server 2 is used for querying all propagation paths and corresponding weights, and an optimal path is provided for the query user through an inadvertent transmission mode. Suppose there are n USERs USER in the system i (i ═ 1,2, …, n). The trusted center 1 distributes and calculates system parameters: ID of user 3, user passwordKey with a key body
Weight key f, query key (sk) 1 ,sk 2 )，USER i Uploading personal sensitive information to a server 2 through encryption, constructing a social graph G (V, E) composed of ciphertext through calculation and integration by the server 2, and providing Identification (ID) of a user and an Identity (ID) of a target user by a query user RU in a user 3 s ,ID t ) The server 2 inquires out all the propagation paths
And corresponding weight value
Inquiring the user decryption weight sequence to obtain the subscript of the optimal propagation path, and transmitting OT through many-to-one carelessness 1 q In this way, the query user can obtain the optimal propagation path.
FIG. 3 is a flowchart of an optimal path matching method for protecting user privacy in a social network according to the present invention. As shown in fig. 3, an optimal path matching method for protecting user privacy in a social network includes:
step 101: the method comprises the following steps that the trusted center generates system parameters and a secret key and sends the system parameters to a server and a user, and specifically comprises the following steps:
and acquiring a safety parameter kappa.
According to the security parameters, calculating a master public key mpk and a master key msk of the encryption algorithm, wherein mpk is (g) msk ,g,p)，
p is a large prime number and satisfies | p | ═ k,
represents [1, p-1 ]]In an arbitrary integer, g is
A generator of (2), selecting a random number R,where R < p/3.
Obtaining a key pair (sk) 1 ,sk 2 ) The key pair includes a first key sk 1 And a second key sk 2 Wherein, in the step (A),
sk 1 +sk 2 ＝mskmod(p-1)。
randomly obtaining n user key vectors
Wherein, the first and the second end of the pipe are connected with each other,
publishing parameters (mpk, g, p, R), i.e. public key for encryption, generator element, prime modulus information and system nonce information for the integration path.
Step 102: the registering of the user specifically includes:
a first registration request is sent.
The trusted center randomly selects an integer from the integer sequence as the identity ID of the current user according to the first registration request i And combining the key vector
And returning to the current user.
Sending the ID to all users connected with the current user i 。
The inquiring user obtains the ID i And then sends a second registration request.
The trusted center returns the first key sk to the inquiring user according to the second registration request 1 。
Step 103: the server performs registration, specifically including:
a third registration request is sent.
The trusted center returns the information to the server according to the third registration requestThe second key sk 2 。
Step 104: the user constructs vertex information and weight information, and sends ciphertext information generated in the process of constructing the vertex information and the weight information to the server, and the method specifically comprises the following steps:
obtaining the USER i The attribute information of (2).
Binarizing the attribute information through one-hot coding to enable the value of only one bit in a binary value corresponding to each dimension attribute to be 1; the current USER USER i Capable of converting all discrete attributes of an individual into an attribute vector of length l
The USER USER i According to the key vector
Encrypting the attribute vector
Deriving vertex information v in a social network i (ii) a Wherein:
USER for each connected USER j The current USER USER i And sending an application to the trusted center.
The trusted center returns a weight key according to the application, specifically
Calculating a weight ciphertext by using the encryption homomorphism property and the weight key, and sending the weight ciphertext to a server; wherein the weight value ciphertext
Calculated using the formula:
wherein rank i,j Is USER i And USER j A predefined integer affinity value between.
And the server integrates the ciphertext to obtain weight information. The specific weight information is:
wherein the weight e i,j Is defined as follows:
step 105: the server is used for constructing a social graph according to the vertex information and the weight information; constructing a social graph G (V, E) according to the vertex information and the weight information, wherein: v ═ V i |i∈[1,n]},E＝{E i,j |i,j∈[1,n],USER i And USER j With a connection }.
Step 106: and the inquiry user in the users uploads the starting end point identification to the server.
Step 107: the server generates a path sequence and a weight sequence according to the social graph and the start and end point identifier, and specifically includes:
determining a vertex v corresponding to a starting point identifier in the social graph s And is defined as a first layer set of starting vertices S 1 (ii) a Finding the vertex v corresponding to the terminal point identification t And is defined as a first layer termination vertex set T 1 。
Determining the first layer starting vertex set S 1 And the first layer termination vertex set T 1 Is denoted as v u Wherein v is u ∈{S 1 ∩T 1 Querying a vertex v according to the social graph s And v u And v u And v t The weights between them are respectively marked as E s,u And E u,t A 1 is mixing E s,u ·E u,t Added to the weight sequence
In, query vertex v simultaneously u Corresponding identification ID u Will ID u Join to Path sequences
In (1).
Determining the first set of starting vertices S from the social graph 1 Each vertex v of i All connected vertices v of j And is defined as a second layer initial vertex set S 2 At the same time v i →v j Adding to a set of prepositioned vertices P 1 。
Determining the second layer starting vertex set S 2 And the first layer termination vertex set T 1 Is updated as v u Wherein v is u ∈{S 2 ∩T 1 At the same time in the set of leading vertices P 1 In finding v u And is denoted by v i Sequentially querying vertexes v according to the social graph s And v i 、v i And v u And v u And v t The weights between are respectively marked as E s,i 、E i,u And E u,t A 1 is mixing E s,i ·E i,u ·E u,t Added to the weight sequence
In, query vertex v simultaneously i And v u Corresponding identity ID i And ID u Will ID i ·R+ID u Join to Path sequence
In (1).
Determining the first-tier set of termination vertices T from the social graph 1 Each vertex v of i′ All connected vertices v of j′ And is defined as a second layer termination vertex set T 2 At the same timeV is to be i′ →v j′ Adding to the post-vertex set P 2 。
Determining the second layer starting vertex set S 2 And the second layer termination vertex set T 2 Is updated as v u Wherein v is u ∈{S 2 ∩T 2 At the same time in the set of leading vertices P 1 In finding v u And is denoted by v i At said set of post-vertices P 2 In finding v u Is denoted by v i′ Sequentially querying vertexes v according to the social graph s And v i 、v i And v u 、v u And v i′ And v i′ And v u The weights between are respectively marked as E s,i 、E i,u 、E u,i′ And E i′,t D, E is to s,i ·E i,u ·E u,i′ ·E i′,t Is added to
In, query vertex v simultaneously i 、v i′ And v u Corresponding identity ID i 、ID i′ And ID u Will ID i ·R 2 +ID u ·R+ID i′ Is added to
In (1), get the path sequence
Sum weight sequence
Step 108: the server sends the weight sequence to the querying user so that the querying user determines the ciphertext position, and the method specifically includes:
according to the second key sk 2 Decrypting the weight sequence
Each element of (a) obtains a first sequence of decryption weights
And sending the information to the inquiring user.
The inquiring user is according to the first key sk 1 Decrypting the first weight sequence
Each element of (2) to obtain a second decryption weight sequence
According to the second decryption weight value sequence
And obtaining the ciphertext position.
Using the second key sk 2 Decipher the weight sequence
Each element of (1) to obtain
And sending to the inquiring user:
first key sk for inquiring user 1 Decipher the weight sequence
Each element of (a):
i.e. w of the final decryption i "for the total weight of each path, by a sorting algorithm, e.g. bubblingAlgorithm, RU can sort out the index of the minimum value, i.e. the ciphertext position
Step 109: the query user determines an optimal path from the path sequence by adopting an inadvertent transmission mode according to the ciphertext position, and the method specifically comprises the following steps:
the server sends q random integers C to the inquiring user h ，
Wherein q is a sequence of paths
Number of elements in, i.e.
The inquiry user calculates q public keys and leads each public key beta 1 ,β 2 ,…,β q Sending the data to the server; wherein random numbers are selected
Computing a b-th said public key beta as a secret key b And the other public keys are calculated by the public keys of the adjacent subscripts and the random integer step by step in two directions to form a chain structure:
β i ＝C i /β i+1 modp,i＝1,2,…,b-1
β b ＝g k modp
β j ＝C j-1 /β j-1 modp,j＝b+1,b+2,…,q
said server checking each of said public keys, i.e. checking C i ＝β i ·β i+1 modp, the inspection result is obtained.
The server encrypts a path sequence by using the public key according to the check result and sends the path sequence to the inquiry user; serviceBy beta i Encrypt m i And sending to the RU:
and the inquiry user decrypts the path ciphertext corresponding to the ciphertext position in the path sequence according to the key k, and can determine the optimal path of the social network through an accidental transmission mode. Namely, the inquiry user decrypts the b-th ciphertext c by using the key k b Obtaining an optimal path
And finally obtaining each vertex identification ID in the optimal path through iterative computation i ＝(m b -(m b modR))/R。
Example 1:
the invention provides an optimal path matching method for protecting user privacy in a social network, which comprises the following steps:
step 1: and generating system parameters.
Step 1.1: the trusted center (TA) selects the security parameter k and calculates the master public key (mpk ═ g) of the ElGamal encryption algorithm msk G, p) and a master key
Wherein p is a large prime number and satisfies | p | ═ κ, g is
A generator of (2). A random number R is selected, where R < p/3.
Step 1.2: TA selects a pair of keys (sk) 1 ,sk 2 ) Wherein
Make sk 1 +sk 2 ＝mskmod(p-1)。
Step 1.3: TA random selection of n user key vectors
Step 1.4: TA issues parameters (mpk, g, p, R).
The entity registration process relates to fig. 4.
Step 2: and (4) registering the entity.
Step 2.1: USER i (i ═ 1,2, …, n) is registered.
Step 2.1.1: USER i (i ═ 1,2, …, n) sends a registration request.
Step 2.1.2: TA randomly selects an integer from the sequence of integers {1,2, …, n } as the user's ID i And will be
And returning to the user.
Step 2.1.3: USER i Sending the ID of the user to all connected users i 。
Step 2.1.4: the querying user RU sends a registration request.
Step 2.1.5: TA Return Key sk to RU 1 。
Step 2.2: the server CS registers.
Step 2.2.1: the server CS sends a registration request.
Step 2.2.2: TA returns the secret key sk to CS 2 。
And step 3: and building a social graph.
Step 3.1: and constructing vertex information.
Step 3.1.1: USER i And (4) binarizing the attribute information of the user by one-hot coding, namely, the value of only one bit in the binary value corresponding to each dimension attribute is 1. Wherein:
sex is male: six i 10; sex is female: six i ＝01。
Age 0-20: age (age) i 100; age 21-50 hours: age (age) i 010; age 50 or above: age (age) i ＝001。
So that all discrete attributes of the user are converted into an attribute vector with each element being a binary value
Where l represents the length of the user's attribute vector.
Step 3.1.2: USER i By means of a secret key
Encryption attribute vector
Forming a vertex
Step 3.2: and constructing weight information.
Step 3.2.1: USER for each connected USER j USER i Sending application to TA
Step 3.2.2: TA query ID j Corresponding user key vector
Calculating and returning weight value key f j,i ：
Step 3.2.3: USER i Computing weight ciphertext by utilizing ElGamal homomorphism property
And sends it to the server CS:
wherein rank i,j Is the USER i And USER j A predefined integer affinity value between.
Step 3.2.4: the CS integrates the ciphertext and forms a weight as:
wherein the weight e i,j Is defined as:
this indicates that the closer the two users are, the faster the message is propagated, so that the weight between the users is smaller.
Step 3.3: from the vertices and edges, a social graph G ═ V, E can be constructed.
Wherein: v ═ V i |i∈[1,n]},E＝{E i,j |i,j∈[1,n],USER i And USER j With a connection }.
And 4, step 4: and (6) path query.
Step 4.1: inquiring the Identification (ID) corresponding to the starting and ending point uploaded by the RU of the user s ,ID t ) To the server CS.
Step 4.2: CS generation path sequence
Sum weight sequence
Step 4.2.1: the CS finds a starting point v in the social graph G s And is defined as a first layer set of starting vertices S 1 (ii) a Finding the end point v t All of (2)And is defined as a first layer set of termination vertices T 1 . Wherein v is not included s And v t 。
Step 4.2.2: CS sorting out S 1 And T 1 Common vertex v in (1) u ∈{S 1 ∩T 1 }, query vertex v s And v u And v u And v t In between, and E s,u ·E u,t Is added to
In (1), v is u Corresponding identity ID u Is added to
In (1).
Wherein:
the homomorphism property of the ElGamal encryption system is used to aggregate the weights of the two connected edges together.
Step 4.2.3: CS finds S in social graph G 1 Each vertex v of i All connected vertices v of j And is defined as the second layer initial vertex set S 2 At the same time v i →v j Adding to a set of prepositioned vertices P 1 (ii) a Wherein v is not included s And v t 。
Step 4.2.4: CS sorting out S 2 And T 1 Common vertex v in (1) u ∈{S 2 ∩T 1 At P } 1 In finding v u Is v as the leading vertex i Querying the vertex v s And v i 、v i And v u And v u And v t In between, and E s,i ·E i,u ·E u,t Is added to
In, query vertex v simultaneously i And v u Corresponding identityIdentification ID i And ID u Will ID i ·R+ID u Is added to
In (1).
Wherein:
step 4.2.5: CS finds T in social graph G 1 Each vertex v of i′ All connected vertices v of j′ And is defined as a second layer termination vertex set T 2 At the same time v i′ →v j′ Adding to the post-vertex set P 2 (ii) a Wherein v is not included s And v t 。
Step 4.2.6: CS sorting out S 2 And T 2 Common vertex v in (1) u ∈{S 2 ∩T 2 At P 1 In finding v u Is v as the leading vertex i At P 2 In finding v u Has a post-vertex of v i′ Sequentially querying vertexes v according to the social graph s And v i 、v i And v u 、v u And v i ' and v i ' and v u A weight value of E between s,i ·E i,u ·E u,i′ ·E i′,t Is added to
In, query vertex v simultaneously i 、v i′ And v u Corresponding identification ID i 、ID i′ And ID u Will ID i ·R 2 +ID u ·R+ID i′ Is added to
In (1).
Wherein:
step 4.3: RU picks out the index b of the optimal path in the path sequence.
Step 4.3.1: secret key sk for CS 2 Decipher weight sequence
Each element of (a) to obtain
And sending to the RU:
step 4.3.2: RU Key sk 1 Decipher the weight sequence
Each element of (a):
i.e. the final decrypted w ″ i For the total weight of each path, through a sorting algorithm, such as a bubble algorithm, the RU may select the subscript corresponding to the minimum value as
The process of inadvertent transmission relates to fig. 5.
Step 4.4: RU inadvertently acquires optimal path m b 。
Step 4.4.1: CS sends q random integers to RU
Wherein q is a sequence of paths
Of (1) elementTo a number of
Step 4.4.2: RU selecting random number
As a key, calculate beta 1 ,β 2 ,…,β q And sending to the CS:
β i ＝C i /β i+1 modp,i＝1,2,…,b-1
β b ＝g k modp
β j ＝C j-1 /β j-1 modp,j＝b+1,b+2,…,q
step 4.4.3: CS examination C i ＝β i ·β i+1 modp。
Step 4.4.4: beta for CS i Encrypt m i And sending to the RU:
step 4.4.5: RU decrypts the b-th ciphertext c by using key k b Obtaining an optimal path
And finally obtaining each vertex identification ID in the optimal path through iterative computation i ＝(m b -(m b modR))/R。
The invention is based on ElGamal homomorphic encryption and inadvertent transmission OT 1 q The method realizes an optimal path matching scheme for protecting the privacy of the user in the social network, and the scheme realizes the resistance to external attack and internal attack.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the embodiment of the present invention are explained by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (3)
1. An optimal path matching method for protecting user privacy in a social network is characterized by comprising the following steps:
the trusted center generates system parameters and a secret key and sends the system parameters to the server and the user;
the user registers;
the server registers;
the user constructs vertex information and weight information and sends ciphertext information generated in the process of constructing the vertex information and the weight information to the server;
the server is used for constructing a social graph according to the vertex information and the weight information;
a query user in the users uploads a starting and ending point identifier to the server;
the server generates a path sequence and a weight sequence according to the social graph and the starting and ending point identification;
the server sends the weight sequence to the inquiry user so that the inquiry user can determine a ciphertext position;
the inquiry user determines an optimal path from the path sequence by adopting an inadvertent transmission mode according to the ciphertext position;
the method comprises the following steps that the trusted center generates system parameters and a secret key, and sends the system parameters to a server and a user, and specifically comprises the following steps:
acquiring a safety parameter kappa;
calculating a master public key mpk and a master key msk of the encryption algorithm according to the security parameters, wherein mpk is (g) msk ,g,p)，
p is a large prime number and satisfies | p | ═ κ,
is [1, p-1 ]]In an arbitrary integer, g is
Selecting a random number R, wherein R < p/3;
obtaining a key pair (sk) 1 ,sk 2 ) The key pair includes a first key sk 1 And a second key sk 2 Wherein, in the process,
sk 1 +sk 2 ＝mskmod(p-1)；
randomly acquiring n user key vectors
Wherein the content of the first and second substances,
issuing parameter information, wherein the parameter information comprises the master public key, the generator, the prime number and the random number;
the registering of the user specifically includes:
sending a first registration request;
the trusted center randomly selects an integer from the integer sequence as the identity ID of the current user according to the first registration request i And combining the key vector
Returning to the current user;
sending the identification ID to all users connected with the current user i ；
The inquiring user obtains the ID i Post-sending second registrationRequesting;
the trusted center returns the first key sk to the inquiring user according to the second registration request 1 ；
The server performs registration, specifically including:
sending a third registration request;
the trusted center returns the second key sk to the server according to the third registration request 2 ；
The user constructs vertex information and weight information, and sends ciphertext information generated in the process of constructing the vertex information and the weight information to the server, and the method specifically comprises the following steps:
obtaining the USER i Attribute information of (2);
binarizing the attribute information through one-hot coding to enable the value of only one bit in a binary value corresponding to each dimension attribute to be 1; the current USER USER i Capable of converting all discrete attributes of an individual into an attribute vector of length l
The current USER USER i According to the key vector
Encrypting the attribute vector
Deriving vertex information v in a social network i ；
USER for each connected USER j The current USER USER i Sending an application to the trusted center;
the trusted center returns a weight key according to the application;
calculating a weight ciphertext by using the encryption homomorphism property and the weight key, and sending the weight ciphertext to a server;
the server integrates the ciphertext to obtain weight information;
the server sends the weight sequence to the query user, so that the query user determines a ciphertext position, which specifically includes:
according to the second key sk 2 Decrypting the weight sequence
Each element of (a) obtains a first sequence of decryption weights
And sending the information to the inquiry user;
the inquiring user is according to the first key sk 1 Decrypting the first decrypted weight sequence
Get a second decryption weight sequence
According to the second decryption weight sequence
Obtaining a ciphertext position;
the method for determining the optimal path from the path sequence by the inquiry user in an oblivious transmission mode according to the ciphertext position specifically comprises the following steps:
the server sends q random integers C to the inquiring user h ，
Wherein q is a sequence of paths
The number of the elements in the Chinese character,
the querying user generates a key
Calculating q public keys and sending each public key to the server, wherein the public key corresponding to the ciphertext position is generated by a secret key k, and the rest public keys are generated according to the public key and the integer C h Generating;
the server checks each public key to obtain a check result;
the server encrypts a path sequence by using the public key according to the check result and sends the path sequence to the inquiry user;
and the inquiry user decrypts the path ciphertext corresponding to the ciphertext position in the path sequence according to the key k, and can determine the optimal path of the social network by an accidental transmission mode.
2. The method as claimed in claim 1, wherein the server generates a path sequence according to the social graph and the start and end point id
Sum weight sequence
The method specifically comprises the following steps:
determining a vertex v corresponding to a starting point identifier in the social graph s And is defined as a first layer starting vertex set S 1 (ii) a Finding the vertex v corresponding to the terminal point identification t And is defined as a first layer termination vertex set T 1 ；
Determining the first layer starting vertex set S 1 And the first layer termination vertex set T 1 Is denoted by v u Wherein v is u ∈{S 1 ∩T 1 According to the societyIntersection query vertex v s And v u And v u And v t The weights between them are respectively marked as E s,u And E u,t D, E is to s,u ·E u,t Is added to
In, query vertex v simultaneously u Corresponding identity ID u Will ID u Is added to
Performing the following steps;
determining the first set of starting vertices S from the social graph 1 Each vertex of (a)
All connected vertices v of j And is defined as the second layer initial vertex set S 2 While v is being measured i →v j Adding to a set of prepositioned vertices P 1 ；
Determining the second layer starting vertex set S 2 And the first layer termination vertex set T 1 Is updated by v u Wherein v is u ∈{S 2 ∩T 1 At the same time in the set of front vertices P 1 In finding v u And is denoted by v i Sequentially querying vertexes v according to the social graph s And v i 、v i And v u And v u And v t The weights between are respectively marked as E s,i 、E i,u And E u,t A 1 is mixing E s,i ·E i,u ·E u,t Is added to
In, query vertex v simultaneously i And v u Corresponding identification ID i And ID u Will ID i ·R+ID u Is added to
Performing the following steps;
determining the first-tier set of termination vertices T from the social graph 1 Each vertex of (1)
All connected vertices v of j′ And is defined as a second layer termination vertex set T 2 While v is being measured i′ →v j′ Adding to the post-vertex set P 2 ；
Determining the second layer starting vertex set S 2 And the second layer termination vertex set T 2 Is updated by v u Wherein v is u ∈{S 2 ∩T 2 At the same time in the set of front vertices P 1 In finding v u And is denoted as v i At said set of post-vertices P 2 In finding v u Is denoted by v i′ Sequentially querying vertexes v according to the social graph s And v i 、v i And v u 、v u And v i′ And v i′ And v t The weights between are respectively marked as E s,i 、E i,u 、E u,i′ And E i′,t A 1 is mixing E s,i ·E i,u ·E u,i′ ·E i′,t Is added to
In, query vertex v simultaneously i 、v i′ And v u Corresponding identification ID i 、ID i′ And ID u Will ID i ·R 2 +ID u ·R+ID i′ Is added to
In (1), get the path sequence
Sum weight sequence
3. A system for protecting user privacy in a social network, the system being configured to implement the optimal path matching method for protecting user privacy in a social network according to any one of claims 1-2, the system comprising: the system comprises a trusted center, a server and a user, wherein the trusted center is used for generating system parameters and a secret key and sending the system parameters to the server; the method comprises the steps that after the user registers, vertex information and weight information are constructed, ciphertext information generated in the process of constructing the vertex information and the weight information is sent to a server, the server is used for constructing a social graph according to the vertex information and the weight information after registering, a query user in the user is used for providing identification marks of the user and a target user, the server is used for querying all propagation paths and corresponding weights, and an optimal path is provided for the query user through an inadvertent transmission mode.
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