A privacy encoding caching method based on virtual users and encoding placement

Abstract

The application discloses a privacy encoding cache method based on virtual users and encoding placement. The method implementation process comprises encoding of cache placement content, encoding of broadcast signals, and decoding of users for requested files. The method is based on virtual users and encoding placement, can be applied to a privacy encoding cache problem of N files and K users, and in the case of file number N=2 and cache size M<=KN, the communication rate is minimum, that is, the size of the required broadcast signal of a transmission unit file is minimum.

Description

Technical Field

[0001] This invention relates to the field of information theory, and in particular to a privacy coding caching method for the privacy coding caching problem with any number of users K and any number of files N. Background Technology

[0002] In schemes designed for the traditional coding caching problem, participating users may know the indexes of files requested by other users, which infringes on user privacy. Therefore, some work has investigated coding caching problems with privacy requirements. Current research only presents order-optimal methods for privacy-preserving coding caching problems, rate-optimal methods for the case of K=2 users, and methods for arbitrary user numbers K and arbitrary number of files N. The optimal speed method for privacy-encoded caching with arbitrary numbers of users K and arbitrary numbers of files N remains an unsolved problem. Summary of the Invention

[0003] Technical Problem: The technical problem to be solved by this invention is to provide a privacy-encoding caching method for privacy-encoding caching of any number of users K and any number of files N. By utilizing caching technology, the communication rate during signal transmission is reduced; by utilizing encoding placement technology, the size of cached content and broadcast signals is further reduced; and by utilizing virtual user technology, no user can deduce the privacy-encoding caching method other than their own request D. k Any information related to request D was obtained using a privacy-encoded caching method based on virtual users and code placement.

[0004] Technical solution: The technical solution adopted in this invention is as follows:

[0005] A privacy-preserving encoding caching method based on virtual users and encoding placement includes the following steps:

[0006] Step 1: Given N files W0, W1, ... W... N-1 The trusted central server generates its own random vector S = (S0, S1, ..., S...). K-1 The key S is distributed to the buffers of users k∈[0:K-1] in the communication system. k and cached content payload The cache consists of two parts, Z, which contains the content. k K represents the number of users in the communication system;

[0007] Step 2: Each user k∈[0:K-1] sends a request D to the central server. k This is used to request any one of N files. The central server processes all user requests, D = (D0, D1, ..., D...).K-1 ), broadcast signal X to all users in the system through a shared link channel. D ;

[0008] Step 3: Each user k∈[0:K-1] according to the received signal X D And the previously cached content Z k Decode the request file

[0009] Furthermore, in step 1, the cached content Z... k The encoding steps are as follows:

[0010] First, the central server will send each file W n ,n∈[0:N-1] partitioned into A set of non-overlapping sub-files of equal size, namely:

[0011]

[0012] Where r∈[0:NK-K+1] is a parameter of this privacy-encoding caching method. It is a set A subset of size r;

[0013] Next, the central server in the limited domain Generate a 1×K random vector S = (S0, S1, ..., S...) K-1 Each element in the vector is independent and identically distributed and follows a uniform distribution, i.e.:

[0014]

[0015] Define a function h as follows:

[0016] h:[0:N-1]×[0:K-1]→[0:N-1] NK-K+1 ,

[0017]

[0018] in:

[0019]

[0020] Finally, the central server sends the cached content Z to user k∈[0:K-1]. k By S k and It consists of two parts, namely:

[0021]

[0022] in By Z k,a In the case of 'a', take S. k When obtained, It is a set A subset of size r+1, and:

[0023]

[0024]

[0025] Furthermore, in step 2, the broadcast signal X D The encoding steps are as follows:

[0026] First, the central server processes all user requests D = (D0, D1, ..., D...). K-1 ) and random vector S = (S0, S1, ..., S K-1 This generates a corresponding vector d = (d0, d1, ..., d2). K-1 ):

[0027]

[0028] in, Represents integer subtraction modulo N;

[0029] Next, the central server generates vector V based on vector d. d and the corresponding set for Vector V d It is given by the following formula:

[0030]

[0031] in, Let represent a unit vector where the i-th bit is 1 and all other bits are 0. Indicates bitwise XOR, for Vector V d Based on other vectors The results were:

[0032]

[0033] V d corresponding set By V d The possible values ​​are given as follows:

[0034]

[0035] Where j∈[0:K-1], V(j) represents the j-th element of vector V;

[0036] Finally, the central server sends a broadcast signal X to user k∈[0:K-1]. D By d and X d It consists of two parts:

[0037]

[0038] Where t d From a set Choose any element from the list. It is obtained by encoding the following formula:

[0039]

[0040] Furthermore, in step 3, each user decodes the request file. The decoding steps are as follows:

[0041] First, for all User k∈[0:K-1] decodes from their own cached content the value not directly stored. And will be used in decoding

[0042]

[0043]

[0044] in, gather yes A subset of , containing N elements, that is, And it satisfies:

[0045]

[0046] It is all those that meet the above three conditions. The set that constitutes;

[0047] Then, similarly, for all User k∈[0:K-1] decodes from the received broadcast signal that there was no direct connection to X. d Transmitted and will be used in decoding

[0048]

[0049]

[0050] Among them, t d The value already determined in step two, g(t), is a value from the set To the request set is Mapping:

[0051]

[0052]

[0053] Finally, user k∈[0:K-1] calculates the file they requested.

[0054]

[0055]

[0056] Beneficial Effects: This invention proposes a privacy-preserving encoding caching method based on virtual users and encoding placement. This method, based on virtual user technology, ensures the privacy of user needs. In the cache placement stage (step one), a new encoding placement method is adopted, and correspondingly, new broadcast signals and decoding methods are designed in steps two and three. The new encoding placement method further reduces the size of the cached content. This method is applicable to privacy-preserving encoding caching problems involving N files and K users, and is suitable for situations where the number of files N=2 and the cache size is... Under these conditions, the communication rate is minimized, meaning the size of the broadcast signal required to transmit a unit of file is minimized. Attached Figure Description

[0057] Figure 1 A system model for the privacy encoding caching problem involving N files and K users. Detailed Implementation

[0058] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention is not limited to the embodiments described.

[0059] like Figure 1 As shown, this invention proposes a privacy-preserving encoding caching method based on virtual users and encoding placement. The system model considers a user who can access N independent files (W0, W1, ... W...). N-1 A central server and K users, each with a cache of size M, are connected via error-free shared links. During the cache content placement phase, the server distributes cache content Z to the caches of users k∈[0:K-1]. k During the signal transmission phase, user k sends a request D to the central server. k The central server processes all user requests, D = (D0, D1, ..., D...). K-1 ), broadcast signal X to all users in the system through a shared link channel. D During the file decoding phase, user k determines the data based on the received signal X. DAnd the previously cached content Z k Decode the request file Throughout the entire process, no user can deduce anything other than their own request D. k Any information related to request D.

[0060] The following is an example:

[0061] This embodiment considers K = 3 users, N = 2 files, and the parameter r = 2 in the method. The specific scheme is as follows:

[0062] (1) The central server will send each file W n The file is divided into 6 non-overlapping subfiles of equal size, where n = 0 and 1.

[0063] W n,{0,1} W n,{0,2} W n,{0,3} W n,{1,2} W n,{1,3} W n,{2,3} n = 1, 2;

[0064] exist A 1×3 random vector S = (S0, S1, S2) is generated, and the central server sends the cached content Z to user k. k By S k and It consists of two parts, namely, in The encoding methods are given in the following table:

[0065]

[0066] (2) The central server generates a corresponding vector d = (d0, d1, d2) based on all user requests D = (D0, D1, D2) and a random vector S = (S0, S1, S2):

[0067]

[0068] in, Represents integer subtraction modulo N; broadcast signal X sent by the central server to user k. D By d and X d It consists of two parts, namely, X D =(X d ,d), where X d The encoding methods are given in the following table:

[0069]

[0070] Where n = 0, 1.

[0071] (3) When D = (D0, D1, D2) = (0, 1, 1) and S = (S0, S1, S2) = (0, 0, 1) in steps (1) and (2), d = (0, 1, 0). Taking user 1 decoding W1 as an example, the decoding methods of user 0 and user 2 are similar. During the decoding process, user 1 first calculates:

[0072]

[0073] Then for all calculate:

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] Other cases follow a similar decoding method.

Claims

1. A privacy-preserving encoding caching method based on virtual users and encoding placement, characterized in that, Includes the following steps: Step 1: The system contains N files. The trusted central server uses its own generated random vectors To users in the communication system The cache distribution is done by the key. and cached content payload The cache consists of two parts. K represents the number of users in the communication system; Step 2, each user Send a request to the central server This is used to request any one of N files. The central server processes all user requests. Broadcast signals are transmitted to all users in the system through a shared link channel. ; Step 3, each user According to the received signal and previously cached content Decode the request file ; In step 1, the cached content is placed. The encoding steps are as follows: First, the central server will process each file. Divided into A set of non-overlapping sub-files of equal size, namely: ； in It is a parameter of the privacy-encoded caching method. , It is a set A subset of size r; Next, the central server in the limited domain Generate a random vectors Each element in the vector is independent and identically distributed and follows a uniform distribution, that is: ； Define a function as follows : ； ； in: ； Finally, the central server sends the data to the user. Cache content Depend on and It consists of two parts, namely: ； in, Depend on In Pick When obtained, It is a set A size is Subset, and: ； Broadcast signal in step 2 The encoding steps are as follows: First, the central server processes all user requests. and random vectors Generate a corresponding vector : ； in, Modulus Integer subtraction; Next, the central server, based on the vector Generate vectors and the corresponding set ,for , ,vector It is given by the following formula: ； in, Let represent a unit vector where the i-th bit is 1 and all other bits are 0. Indicates bitwise XOR, for ,vector Based on other vectors The results were: ； corresponding set Depend on The possible values ​​are given as follows: ； in , Representing vectors The Bit; Finally, the central server sends the data to the user. broadcast signal Depend on and It consists of two parts: ， in From a set Choose any element from the list. It is obtained by encoding the following formula: ； In step 3, each user decodes the request file. The decoding steps are as follows: First, for all ,user Decode from its own cached content what is not directly stored And will be used in decoding : ； in, ,gather yes A subset of , containing N elements, that is, And satisfy: ； It is all those that meet the above three conditions. The set that constitutes; Then, similarly, for all ,user Decode from the received broadcast signal that there was no direct passage Transmitted and will be used in decoding : ； in, It is the value that was already determined in step two. It is from a set To request set Mapping: ； ； Finally, the user Calculate the file you requested : ； 。

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