KR20120002729A - Search system and method in multi-user - Google Patents

Abstract

PURPOSE: A search system between multi users for an encryption document and a method thereof are provided to search and transmit an encryption document related to a keyword of a user and decrypt the document by an encryption key, thereby preventing data tapping. CONSTITUTION: A user list managing unit(210) manages a second secret key including the identification information of a user and a first secret key. A key generating unit(230) generates a first generation key for generating a document encryption key and a second generation key for generating a keyword index generation key using a random number and the second secret key received from a user terminal. A data searching unit(240) generates the keyword index generation key based on a query value and the second secret key received from the user terminal and searches an encrypted document corresponding to the keyword index generation key.

Description

Multi-party search system and method thereof {SEARCH SYSTEM AND METHOD IN MULTI-USER}

The present invention relates to a multi-party retrieval system and method for ensuring security and providing efficient keyword retrieval.

Recently, with the development of cloud computing technology, cloud-based storage services that can share data through the Internet have attracted attention. Through the storage service, user terminals may upload their data to a public server and download materials of interest.

However, the sharing of data through a public server increases the convenience of the user terminals, but there is a problem with respect to the privacy of the user terminals. Since data stored in public servers are managed by service providers rather than user terminals, data exposure by untrusted service providers is difficult to solve by simple access control.

In addition, although data may be encrypted and stored to prevent data exposure to untrusted service providers, such data encryption dramatically degrades the efficiency of retrieval.

In order to solve such a search problem, researches for searching documents encrypted using keywords based on symmetric key and public key have been actively conducted. In the keyword search based on symmetric key, the user terminal encrypts the data with its symmetric key and stores it in the server, and then searches the document using its symmetric key. Search is possible.

In addition, the public key-based keyword retrieval technique encrypts the data retrieval information with the public key of the user terminal together with the encrypted data and stores the data retrieval in the server. At this time, only the person who owns the secret key corresponding to the public key used for encryption can search. However, in a symmetric key and public key based search method, only a specific user terminal can search. Therefore, this technique is not suitable for an environment in which multiple user terminals share data through public servers.

If the N user terminals share data with each other, the user terminal uploading the data must encrypt and store the same data N times so that a document can be searched for all N user terminals. This is very inefficient in terms of storage.

On the other hand, in recent years, a method for searching a document while protecting the privacy of user terminals in a multi-party data sharing environment has been proposed. However, since there is only one specific user terminal capable of uploading data, the user terminal capable of uploading data first determines other user terminals to download the data before uploading the data, and then only those other user terminals can download the data. Encrypt the data so that it can be stored. Therefore, this method is not suitable for an environment in which several user terminals upload their data.

In addition, since the user terminals that can be searched in advance are designated, it is difficult to manage the subscribers or withdrawals in the future. For example, since broadcast encryption is used for the revocation process, every other user terminal needs to update a new value every time the withdrawal occurs. In addition, the subscriber or withdrawal process is very inefficient because the encrypted index of all data must be modified for the subscriber or withdrawal process.

In addition, there are methods suitable for a multi-party data sharing environment in which various user terminals upload and download their own data with respect to the encrypted data. However, there is an insecure aspect against a passive attack of the withdrawal. That is, when the user terminal withdraws, the document cannot be searched, but when eavesdropping the data searched by another user terminal, all the eavesdropping data can be decrypted.

One embodiment of the present invention is to provide a multi-party retrieval system and method that can be guaranteed multi-party security, and can efficiently retrieve encrypted documents.

In addition, an embodiment of the present invention, while searching for and transmitting an encrypted document related to a keyword included in the query, for an effective and convenient withdrawal processing and a query of a user requesting a keyword search for an encrypted document, the encrypted document It is an object of the present invention to provide a multi-party retrieval system and a method for solving the problem of data eavesdropping by an external attacker by enabling the decryption using the calculated document encryption key.

In addition, an embodiment of the present invention by generating a query using the private key that the user has been duly issued for the encrypted document to be searched by keyword, an external attacker can create a legitimate query for malicious purposes It is an object of the present invention to provide a multi-party retrieval system and its method, which can ensure the stability of a query.

As a technical means for achieving the above technical problem, the multilateral retrieval system according to the first aspect of the present invention, according to the user registration request, issuing a first secret key to the user terminal of the user who requested the user registration, the first secret A user management unit that provides a document management unit with a second secret key generated to include a key and identification information of the user, a random number received from a user terminal, and a second secret key used to generate a document encryption key for encrypting a document. Generating a second generation key used to generate the keyword index generation key for encrypting the first generation key and the keyword for the document and providing the second generation key to the user terminal, and storing the encrypted document and the encrypted keyword received from the user terminal. Including a document management unit, the encrypted document is used by the document encryption key generated based on the first generation key The encrypted keyword is encrypted in the user terminal, and the encrypted keyword is encrypted in the user terminal by the keyword index generation key generated based on the second generation key.

Here, the user terminal generates a query value including the keyword, the user's identification information, and the first secret key of the user terminal according to the user's keyword input, transmits the query value to the document manager, and decrypts the encrypted document received from the document manager. .

When the user is a user registered in the user list, the document manager calculates a keyword index generation key based on the query value and the user's second secret key, and searches for an encrypted document corresponding to the calculated keyword index generation key. Then, the encrypted document and the first generation key for the encrypted document are transmitted to the user terminal.

Further, the user terminal calculates a document encryption key for the encrypted document from the first generation key received from the document management unit, and decrypts the encrypted document based on the calculated document encryption key.

The document manager may further include a user list manager that manages a second secret key generated for each user to include identification information of the user who requested user registration and a first secret key, a random number received from a user terminal, and a second secret key. A key generation unit for generating a first generation key used for generation of a document encryption key and a second generation key for generation of a keyword index generation key, an encrypted data storage unit for storing an encrypted document and an encrypted keyword, and a query Calculates a keyword index generation key based on the value and the second secret key of the user, searches for an encrypted document corresponding to the calculated keyword index generation key, and uses the first generation key for the encrypted document and the encrypted document. It includes a data search unit for transmitting to the terminal.

Here, the user list manager removes the identification information of the user who requested to withdraw the user and the second secret key of the user who requested to withdraw the user from the user list.

Also, the user terminal generates a document encryption key to encrypt a document to be stored in the document management unit, and generates a keyword index generation key to encrypt a keyword for the document, a keyword according to the user's keyword input, identification of the user A document encryption key for the encrypted document is calculated from the query generation unit for generating a query value including the information and the first secret key of the user terminal and the first generation key received from the document management unit, and based on the calculated document encryption key. And a data decryption unit for decrypting the encrypted document.

In addition, the user manager may include a user list manager that manages identification information of a user who has requested user registration as a user list and a first secret key and document manager that will be issued to a user terminal of a user who has requested user registration using a private key of the user manager. And a key generator for generating a second secret key generated to include a first secret key to be provided to the.

In the multi-party retrieval method according to the second aspect of the present invention, in response to a user registration request, the user management apparatus issues a first secret key to a user terminal of a user who has requested a user registration, and generates a second secret key to be included. Providing a secret key and identification information of the user to the document server; a first generating key and a document used for generating a document encryption key for encrypting a document using a random number received from the user terminal and a second secret key; Generating and providing a second generation key used to generate a keyword index generation key for encrypting a keyword to the user terminal and encrypting the document server using a document and keyword index generation key encrypted using the document encryption key And receiving the stored keyword from the user terminal, wherein the document encryption key is based on the first generation key. And gender, keywords, the index generated key is generated based on the second generation key.

Here, when the document server is a user registered in the user list, the document server calculates a keyword index generation key based on the query value received from the user terminal and the user's second secret key, and corresponds to the calculated keyword index generation key. Retrieving the encrypted document, and transmitting the encrypted document and a first generation key for the encrypted document to the user terminal.

In this case, the user terminal generates a query value including the keyword, the user's identification information, and the first secret key of the user terminal according to the user's keyword input.

The user terminal also calculates a document encryption key for the encrypted document from the first generation key received from the document server, and decrypts the encrypted document based on the calculated document encryption key.

In accordance with a third aspect of the present invention, a multilateral retrieval system according to a user registration request, issues a first secret key to a user terminal of a user who has requested a user registration, and generates a second secret key and a user to include the first secret key. The user management device that provides the identification information of the document server, generates a document encryption key to encrypt the document to be stored in the document server, generates a keyword index generation key to encrypt the keyword for the document, encrypted documents and encrypted keywords Using the user terminal for transmitting the document server to the document server, the random number received from the user terminal, and the second secret key used for generating the document encryption key and the second generated key used for generating the keyword index generation key. Documents generated and provided to the user terminal and storing the encrypted document and the encrypted keyword received from the user terminal And a server, wherein the user terminal generates a document encryption key based on the first generation key, and generates a keyword index generation key based on the second generation key.

Here, the user terminal generates a query value including the keyword, the user's identification information, and the first secret key of the user terminal according to the user's keyword input, transmits the query value to the document server, and decrypts the encrypted document received from the document server. .

When the user is a user registered in the user list, the document server calculates a keyword index generation key based on the query value and the user's second secret key, and searches for an encrypted document corresponding to the calculated keyword index generation key. Then, the encrypted document and the first generation key for the encrypted document are transmitted to the user terminal.

The user terminal also calculates a document encryption key for the encrypted document from the first generation key received from the document server, and decrypts the encrypted document based on the calculated document encryption key.

According to any one of the problem solving means of the present invention described above, multilateral security can be ensured, it is possible to search the encrypted document efficiently.

In addition, according to any one of the above-described problem solving means of the present invention, with respect to the query of the user who requested an effective and convenient withdrawal processing and the keyword search for the encrypted document, the encrypted document related to the keyword included in the query is retrieved And transmit the encrypted document using the calculated document encryption key, thereby eliminating the problem of data eavesdropping by an external attacker.

In addition, according to any one of the above problem solving means of the present invention, by generating a query using the private key that the user has duly issued for the encrypted document to be searched by the keyword, the external attacker has a malicious purpose This makes it impossible to create a valid query, so that the stability of the query can be secured.

1 is a block diagram of a multi-party search system according to an exemplary embodiment of the present invention.
2 is a block diagram of a user management apparatus according to an embodiment of the present invention.
3 is a block diagram of a document server according to an embodiment of the present invention.
4 is a block diagram of a user terminal according to an embodiment of the present invention.
5 is a diagram illustrating a setup, registration, and withdrawal process of a multi-party search system according to an embodiment of the present invention.
6 illustrates a storage process of a multi-party search system according to an embodiment of the present invention.
7 illustrates a query and search process of a multi-party search system according to an embodiment of the present invention.
8 is a flowchart of a multi-party search method according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

1 is a block diagram of a multi-party search system according to an exemplary embodiment of the present invention.

”라고도 함)(100), 문서 서버(이하 “

”라고도 함)(200) 및 사용자 단말(이하, “

” 라고도 함)(300)를 포함한다.As shown in FIG. 1, the multi-party retrieval system has a user management apparatus (hereinafter, “

100, document server (hereinafter referred to as “

200 and user terminal (hereinafter referred to as “

300 ”.

According to the user registration request, the user management apparatus 100 issues a first secret key to the user terminal 300 of the user who requested the user registration, and identifies the second secret key and the user generated to include the first secret key. Information is provided to the document server 200.

개의 데이터(

)가 암호화된 형태이며, 속성 중의 하나는 문서를 검색하기 위한 키워드를 포함할 수 있다.The document server 200 stores the identification information and the second secret key of the user received from the user management apparatus 100. In addition, the document server 200 receives and stores encrypted data including an encrypted document and an encrypted keyword for the document from the user terminal 300. Specifically, encrypted data consists of multiple attributes

Data (

) Is in encrypted form, and one of the attributes may include a keyword for searching for a document.

In addition, the document server 200 may generate a random number received from the user terminal 300 with a first generation key for generating a document encryption key and a second generation key for generating a keyword index generation key for encrypting a keyword for a document; The second secret key may be generated and provided to the user terminal 300.

In addition, when the user is a user registered in the user list, the document server 200 calculates a keyword index generation key based on the query value received from the user terminal 300 and the second secret key of the user, and calculates the keyword. The encrypted document corresponding to the index generation key is searched, and the encrypted document and the generation key for the encrypted document are transmitted to the user terminal 300.

The user terminal 300 generates a document encryption key to encrypt a document to be stored in the document server 200, generates a keyword index generation key to encrypt a keyword for the document, and converts the encrypted document and the encrypted keyword into a document server ( 200). In this case, the user terminal 300 may generate a document encryption key based on the first generation key received from the document server 200, and generate a keyword index generation key based on the second generation key.

In addition, the user terminal 300 generates a query value including the keyword, the user's identification information and the first secret key of the user terminal 300 according to the user's keyword input and transmits to the document server 200, the document server The encrypted document received from 200 may be decrypted.

Here, the user terminal 300 receives the encrypted document and the generation key for the encrypted document from the document server 200, calculates a document encryption key for the encrypted document from the generation key, and calculates the document encryption key Based on the encrypted document can be decrypted.

Hereinafter, each component of the multilateral search system will be described in more detail with reference to FIGS. 2 to 4.

2 is a block diagram of a user management apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the user management apparatus 100 includes a user list manager 110 and a key generator 120.

The user list manager 110 manages identification information of a user who has requested user registration as a user list. For example, the user list manager 110 may include identification information of a user who has requested user registration in a user list of the user management apparatus 100 or include identification information of a user who has requested to withdraw the user from the user list of the user management apparatus 100. Can be removed from.

The key generation unit 120 uses the secret key of the user management apparatus 100 to provide the first secret key to be issued to the user terminal 300 of the user who has requested the user registration and the first secret key to be provided to the document server 200. Generate a second secret key generated to include.

3 is a block diagram of a document server according to an embodiment of the present invention.

As shown in FIG. 3, the document server 200 includes a user list manager 210, an encrypted data storage 220, a key generator 230, and a data searcher 240.

The user list manager 210 manages a second secret key generated for each user to include identification information of the user who requested user registration and a first secret key. Here, the user list manager 210 may remove the identification information of the user who has requested to withdraw the user and the second secret key of the user who has requested to withdraw the user from the user list.

Therefore, since the identification information and the secret key of the withdrawn user are deleted, the document can be securely protected from the withdrawn external user.

The encrypted data storage unit 220 stores the encrypted document and the encrypted keyword received from the user terminal 300.

The key generation unit 230 uses the random number and the second secret key received from the user terminal 300 to generate the first generation key used for generating the document encryption key and the second generation key used for generating the keyword index generation key. Create

Here, the first generation key and the second generation key may be delivered to the user terminal 300 and used to generate a document encryption key for encrypting a document and a keyword index generation key for encrypting a keyword for the document, respectively. .

The data retrieval unit 240 calculates a keyword index generation key based on the query value received from the user terminal 300 and the user's second secret key, and retrieves an encrypted document corresponding to the calculated keyword index generation key. The searched encrypted document and a generation key for the encrypted document are transmitted to the user terminal 300.

Here, the user terminal 300 receives the retrieved encrypted document and a generation key for the encrypted document from the document server 200, calculates a document encryption key for the encrypted document from the corresponding generation key, and calculates the document encryption. It is possible to decrypt the encrypted document based on the key.

Therefore, for the query of the user who requested the keyword search for the encrypted document, the encrypted document related to the keyword included in the query is searched and transmitted, and the encrypted document can be decrypted using the calculated document encryption key. By doing so, it is possible to solve the problem of data eavesdropping by external attacker.

4 is a block diagram of a user terminal according to an embodiment of the present invention.

As shown in FIG. 4, the user terminal 300 includes an identification information management request unit 310, a data encryption unit 320, a query generator 330, and a data decryption unit 340.

The identification information management request unit 310 transmits identification information of the user to the user management apparatus 100 to perform a request for registration or withdrawal of the identification information.

The data encryption unit 320 generates a document encryption key to encrypt a document to be stored in the document server 200, and generates a keyword index generation key to encrypt a keyword for the document. In this case, the document encryption key may be generated based on the first generation key, and the keyword index generation key may be generated based on the second generation key.

The query generator 330 generates a query value including a keyword, user identification information, and a first secret key of the user terminal 300 according to a user's keyword input.

The data decryption unit 340 receives the encrypted document and the generation key for the encrypted document from the document server 200, calculates a document encryption key for the encrypted document from the generation key, and calculates the calculated document encryption key. Decrypt the encrypted document on the basis of

표기는 집합

의 원소

를 랜덤하게 선택하는 것을 나타내며,

는 집합

의 크기를 나타낸다. 또한,

표기는 알고리즘 에서

를 출력하는 것을 나타낸다. 그리고

표기는 모든 양의 정수

에 대하여 정수

가 존재하고,

를 만족할 때 무시할 수 있을 만큼 작은 값으로 수렴하는 함수(negligible function)로 정의된다.Meanwhile, in the following embodiments of the present invention, for example,

Notation is a set

Element of

Indicates a random selection of

Set

Indicates the size. Also,

Notation Algorithm in

Outputs. And

Notation is any positive integer

Against integer

Is present,

Is defined as a negligible function that converges to a value that can be ignored when satisfying.

In addition, a pseudorandom function used in an embodiment of the present invention is defined as a function having an output value that cannot be efficiently distinguished from an output value of a random function. Specifically, pseudorandom functions

는 시드(seed) 값의 비트수,

은 입력 값의 비트수,

은 출력 값의 비트수를 나타낸다. Can be defined as

Is the number of bits in the seed,

Is the number of bits in the input value,

Represents the number of bits in the output value.

,

)는 일반적으로 의사난수 함수로부터 모델링된다. 이때, 의사난수 함수 중에서 입력 값의 비트수와 출력 값의 비트수가 같을 경우, 이것을 의사난수 치환(pseudorandom permutation)이라고 정의한다. 구체적으로 의사난수 치환은

Further, cryptographic hash functions (e.g., described below) used in embodiments of the present invention

,

) Is usually modeled from a pseudorandom function. In this case, when the number of bits of the input value and the number of bits of the output value in the pseudo random number function are the same, this is defined as pseudorandom permutation. Specifically, pseudo random number substitution

가 의사 난수 치환으로,

가 의사 난수 함수로 모델링될 수 있다.It can be defined as. In general, secure symmetric key cryptography is modeled using pseudo-random substitution. For example, to be described later

Is a pseudo random number substitution,

Can be modeled as a pseudo-random function.

와

이 소수 위수

를 가지는 두 개의 군이라 하고, 겹선형 사상을

라고 하면, 이하의 (가) 내지 (다)를 만족한다.In addition, embodiments of the present invention employ some finite group of prime numbers that provide bilinear maps. for example

Wow

This decimal number

Are called two groups with

In this case, the following (a) to (c) are satisfied.

와 모든

에 대해

를 만족한다. 참고로,

는 암호화에 이용되는 대칭키를 나타내고,

는 상수를 나타낸다.(A) All

And all

About

. Note that,

Represents the symmetric key used for encryption,

Represents a constant.

가 군

의 생성자이면,

는 군

의 생성자이다.(B) if

Gagun

If is a constructor of,

County

Is the constructor of.

는 계산하기 쉬워야 한다.(C) arbitrary elements About

Should be easy to calculate.

를 겹선형 사상과 동일하게 정의하고,

를 군

의 생성자, 충돌 저항성 해시 함수를

, 사용자 단말의 서명키를

, 검증키를

라고 정의한다. In addition, the BLS short signature used in the embodiment of the present invention is a signature technique based on the parallelism proposed by Boneh et al. For example, the BLS short signature variables

Defines the same as the double line mapping,

County

Constructor, collision-resistant hash function

, The signature key of the user terminal

, Validation key

It is defined as.

에 대한 서명을

라고 하면, 이에 대한 검증은

을 통해 가능하다. BLS 짧은 서명은 CDH(Computational Diffie-Hellman) 문제의 어려움에 기반하여 랜덤 오라클 모델에서 서명 위조 불가능성을 만족한다.Where message

Sign for

If you say, the verification

It is possible through. The BLS short signature satisfies the signature forgery in the random Oracle model based on the difficulty of the Computational Diffie-Hellman problem.

Hereinafter, an operation of the multiparty search system that provides multiparty keyword search according to each process will be described in detail with reference to FIGS. 5 to 7.

5 is a diagram illustrating a setup, user registration, and user withdrawal process of a multi-party search system according to an embodiment of the present invention.

)와 자신의 비밀키(

)를 생성한다. As shown in FIG. 5, in the setup process, the user management apparatus 100 may display a public parameter (

) And your private key (

)

)를 이용하여 공개 파라미터(params)를 설정하고, 자신의 비밀키(

)를 랜덤하게 선택한다. Specifically, the user management apparatus 100 may include a security parameter (for example, a security parameter).

Set public parameters with your own private key (

) Is randomly selected.

), 충돌 저항성(collision resistance) 해시함수(

), 해시함수의 시드값(

)을 랜덤하게 선택하고, 시드를 포함하는 충돌 저항성 해시함수(

)를 설정한다. 여기서

는 키들의 집합,

는 시드들의 집합,

는 키워드들의 집합을 나타낸다.And secure symmetric key cryptography (

), Collision resistance hash function (

), The seed of the hash function (

) And randomly select the collision-resistant hash function containing the seed (

). here

Is a set of keys,

Is a set of seeds,

Represents a set of keywords.

)을 이용하여 사용자 등록을 요청한 사용자에게 제공할 비밀키(

)를 생성하여 발급한다. Next, in the user registration (Join) process, when the user requests the user registration to the user management apparatus 100, the user management apparatus 100 has its own secret key value (

Secret key to be provided to the user who requested user registration using

) And issue it.

)(또는 고유정보)를 전송하면, 사용자 관리장치(100)은 해당 식별정보(

)를 사용자 관리장치측 사용자 리스트(

)에 포함시킨다. In more detail, the user who wants to register a user identification information (

(Or unique information), the user management apparatus 100 is the corresponding identification information (

) User management device side user list (

).

(제 1 비밀키)를 랜덤하게 선택하고, 자신의 비밀키(

) 및 제 1 비밀키를 이용하여 문서 서버(200)에 제공할 비밀키

(제 2 비밀키)를 생성한다. 여기서, 제 2 비밀키는 사용자의 식별정보(

)에 대응된 정보일 수 있다.And the user management apparatus 100 is the user's secret key

Randomly select (the first secret key),

And a secret key to be provided to the document server 200 using the first secret key.

Create a (second secret key). Here, the second secret key is the identification information of the user (

) May correspond to information.

), 문서 서버(200)에 사용자의 식별정보 및 제 2 비밀키(

)를 각각 전송한다. 여기서, 문서 서버(200)는 자신의 사용자 리스트(

)에 사용자의 식별정보 및 제 2 비밀키를 포함시킨다.In addition, the user management apparatus 100 transmits the seed value of the first secret key and the hash function to the user terminal 300.

), The identification information of the user and the second secret key (

) Respectively. Here, the document server 200 has its own user list (

) Includes the user's identification information and the second secret key.

)를 사용자 리스트(

)에서 제거하고, 문서 서버(200)에 해당 사용자의 식별정보(

)를 전송한다. 그러면, 문서 서버(200)는 자신의 사용자 리스트(

)에서 사용자 탈퇴를 요청한 사용자의 식별정보 및 제 2 비밀키(

)를 제거하게 된다.Next, in the user withdrawal (Revoke) process, the user management apparatus 100 is a user (requesting to withdraw the user)

) List of users (

) And the identification information of the user in the document server 200 (

). Then, the document server 200 has its own user list (

Identification information and the second private key (

) Will be removed.

6 illustrates a storage process of a multi-party search system according to an embodiment of the present invention.

(즉,

)를 이용하여 문서(

)와 상기 문서에 대한 키워드(

)를 암호화한 암호화된 데이터(

)를 문서 서버(200)로 전송한다.As shown in FIG. 6, in the data store process, the user terminal 300 receives the user management device 100 from the user management apparatus 100.

(In other words,

) To view the document (

) And keywords for these documents (

) Encrypted data (

) Is transmitted to the document server 200.

)가 사용자 리스트(

)에 등록되었는지 여부를 검사하고,

를

에 저장한다. 참고로, 문서 서버(200)에

(양의 정수) 번째 저장되는 문서와 키워드를 각각

라고 하면,

를 암호화한 암호화된 데이터는

로 표기되고, 이러한

들의 집합은

로 표기된다.Then, the document server 200 identifies the user's identification information (

) List of users (

) Is registered as

To

Store in For reference, the document server 200

(Positive integer) the second stored document and keywords

Speaking of

Encrypted data is encrypted

Denoted as

Set of things

It is indicated by.

)를 암호화하기 위한 문서 암호화키(

) 및 키워드(

)에 대한 키워드 인덱스 생성키(

)를 생성하기 위해, 먼저 난수(

)와 난수(

)를 랜덤하게 선택하고, 난수화된 키워드(

) 정보를 포함하는

를 생성하여 문서 서버(200)로 전송한다. 여기서,

및

는 난수화 값으로 각각

및

를 생성할 때 사용될 수 있다.More specifically, the user terminal 300 is a document (

Document encryption key (

) And keywords (

Keyword index key for)

To generate), first create a random number (

) And random numbers (

) Randomly, and randomized keywords (

) Containing information

Generate and transmit to the document server 200. here,

And

Are randomized values, respectively

And

Can be used when generating

)가 등록되어 있는지 여부를 검사하고, 문서 암호화키 및 키워드 인덱스 생성키(

및

)를 생성하기 위한 제 1 및 제 2 생성키 값(

및

)을 상술된 겹선형 사상 함수를 이용하여 아래 수학식 (1) 및 (2)와 같이 생성해서 사용자 단말(300)로 전송한다. The document server 200 then identifies the user's identification information (

) Is registered, and the document encryption key and keyword index generation key (

And

First and second generation key values () for generating

And

) Is generated as shown in the following equations (1) and (2) by using the above-described layered mapping function and transmitted to the user terminal 300.

[Equation 1]

[Equation 2]

) 및 난수화된 키워드(

) 정보를 포함하는

정보가 이용될 수 있다. Here, the second secret key value corresponding to the identification information of the user received from the user management apparatus 100 described above (

) And randomized keywords (

) Containing information

Information may be used.

) 정보가 사용자 리스트(

)에서 삭제되어 있으므로, 근본적으로 문서를 검색하기 위한 키워드에 대한 키워드 인덱스 생성키가 생성될 수 없다.In addition, the withdrawn user terminal described above may have a second secret key (

Information in the user list (

), A keyword index generation key for a keyword for searching a document can not be generated.

및

)을 이용하여 문서(

)를 암호화하기 위한 문서 암호화키(

) 및 키워드(

)에 대한 키워드 인덱스 생성키(

)를 아래 수학식 (3) 및 (4)와 같이 생성할 수 있다. 이때, 사용자 관리장치(100)로부터 수신한 제 1 비밀키가 이용될 수 있다.In addition, the user terminal 300 receives the first and second generation key values received from the document server 200 (

And

) To view the document (

Document encryption key (

) And keywords (

Keyword index key for)

) Can be generated as in Equations (3) and (4) below. In this case, the first secret key received from the user management apparatus 100 may be used.

&Quot; (3) "

&Quot; (4) "

)를 문서 암호화키 값(

)을 이용하여

로 암호화하고,

를 검색하기 위한 키워드를 인덱스 생성키 값(

)을 이용하여 암호화한다. 이때, 랜덤한 난수(

)를 선택하고, 해당 난수(

) 및 키워드 인덱스 생성키 값(

)을 이용하여 암호화된 키워드(

)를 생성할 수 있다.Here, the user terminal 300 is a document that you want to save (

) Is the document encryption key value (

)

Encrypted with

Create a keyword to search for an index key value (

) To encrypt. Where random random numbers (

), Select the appropriate random number (

) And keyword index generation key values (

) Encrypted using

) Can be created.

)를 적용시킴으로써, 같은 키워드에도 다른 인덱스 값을 생성하게 되어 외부 공격자에 의한 정보 노출의 위험을 막을 수 있게 된다.Where random number (

By applying), different index values can be generated for the same keyword, thereby preventing the risk of information disclosure by an external attacker.

)에 난수(

) 및 해당 난수가 적용된 암호화된 키워드(

)가 문서 서버(200)에 전송되어진다.Next, the user terminal 300 generates a set of encrypted data as shown in Equation 5 and stores it in the document server 200. Where index (

) To random numbers

) And encrypted keywords with their random numbers (

) Is transmitted to the document server 200.

[Equation 5]

7 illustrates a query and search process of a multi-party search system according to an embodiment of the present invention.

)를 생성한다. As illustrated in FIG. 7, in the query process, the user terminal 300 requests a document server 200 to request the document server 200 by using the user's identification information, a keyword, and a first secret key thereof.

)

을 생성하여 문서 서버(200)로 전송한다. In other words,

Create and transmit to the document server 200.

Here, since the query is generated through the first private key of the user received from the user management apparatus 100, the external attacker can not generate a valid query, the stability of the query can be secured.

)를 전송하고 그에 대응되는 응답 데이터(

)를 수신한다. 그리고, 사용자 단말(300)는 응답 데이터로부터 암호화된 문서를 복호화하게 된다.In the search process, the user terminal 300 queries a document server (

) And the corresponding response data (

). In addition, the user terminal 300 decrypts the encrypted document from the response data.

)를 수신한 문서 서버(200)는, 사용자 리스트(

)에 해당 식별정보가 등록되어 있는지 여부를 확인하고, 만약 등록된 정보가 존재하지 않으면 정당한 사용자 단말이 아니므로 종료한다. 만약 해당 사용자에 대한 등록된 정보가 존재할 경우, 문서 서버(200)는 사용자 단말(300)로부터 수신한 쿼리값 및 해당 사용자의 제 2 비밀키에 기초하여 키워드 인덱스 생성키(

)를 다음과 같이 산출한다.In more detail, the query from the user terminal 300 (

), The document server 200 receives the user list (

Check whether the corresponding identification information is registered, and if the registered information does not exist, the terminal is terminated because it is not a valid user terminal. If there is registered information on the user, the document server 200 generates a keyword index generation key based on the query value received from the user terminal 300 and the second secret key of the user.

) Is calculated as follows.

And document server 200,

)중에서 키워드 인덱스 생성키에 대응되는 암호화된 문서를 검색한다. Set of

), The encrypted document corresponding to the keyword index generation key is retrieved.

) 및 암호화된 문서에 대한 제 1 생성키(

)을 생성하여 사용자 단말(300)로 전송한다. Then, the retrieved encrypted document (

) And the first generation key for the encrypted document (

) Is generated and transmitted to the user terminal 300.

)를 아래와 같이 산출하고, 산출한 문서 암호화키에 기초하여 암호화된 문서를 복호화하게 된다.Then, the user terminal 300 is a document encryption key for the document encrypted using the first generation key (

) Is calculated as follows, and the encrypted document is decrypted based on the calculated document encryption key.

8 is a flowchart of a multi-party search method according to an embodiment of the present invention.

The user terminal 300 performs a user registration request to the user management apparatus 100 (S801).

Next, in response to the user registration request, the user management apparatus 100 issues a first secret key to the user terminal 300 of the user who requested the user registration (S802).

Then, the second secret key generated to include the first secret key and the identification information of the user are provided to the document server 200 (S803).

Next, the user terminal 300 transmits a random number to the user management apparatus 100 (S804).

Next, the document server 200 uses the random number and the second secret key received from the user terminal 300 to generate the first generation key and the keyword index generation key used to generate the document encryption key. A generation key is generated and provided to the user terminal 300 (S805).

Next, the user terminal 300 generates a document encryption key based on the first generation key, and generates a keyword index generation key based on the second generation key (S806).

The user terminal 300 encrypts the document using the document encryption key generated based on the first generation key, and encrypts the keyword using the keyword index generation key generated based on the second generation key. In step S807, S808.

Next, the document server 200 receives and stores the encrypted document and the encrypted keyword from the user terminal 300 (S809).

Next, the user terminal 300 generates a query value and transmits it to the document server 200 (S810 and S811). Here, the user terminal 300 may generate a query value including a keyword, user identification information, and a first secret key of the user terminal 300 according to a user's keyword input.

Next, the document server 200 determines whether the corresponding user is a user registered in the user list (S812).

Next, when the user is a user registered in the user list, the document server 200 calculates a keyword index generation key based on the query value received from the user terminal 300 and the user's second secret key, and calculated The encrypted document corresponding to the keyword index generation key is retrieved (S813).

Next, the document server 200 transmits the encrypted document and the first generation key for the encrypted document to the user terminal 300 (S814).

Next, the user terminal 300 calculates a document encryption key for the encrypted document from the first generation key received from the document server 200, and decrypts the encrypted document based on the calculated document encryption key (S815). ).

Subsequently, when the document server 200 receives the user withdrawal request from the user terminal 300, the document server 200 removes the identification information of the user who requested to withdraw the user and the second secret key of the user who requested to withdraw the user from the user list.

)가 동일한 키워드(

)를 이용하여 생성한 쿼리By using the above-described processes (S801 to S809), for example, other legitimate users (

) Have the same keyword (

Generated using)

을 문서 서버(200)로 전송하면, 문서 서버(200)는 In other words,

To the document server 200, the document server 200

을 생성한다.

.

이므로, 다른 사용자는 사용자가 저장한 데이터를 암호화된 상태로 전송받을 수 있다. 그리고, 다른 사용자는 문서 서버(200)로부터 전송받은

로부터

를 생성하고,

이므로, 다른 사용자는 사용자가 저장한 암호화된 문서를 정당하게 복호화할 수 있게 된다.then,

Therefore, the other user can receive the data stored by the user in an encrypted state. And, the other user received from the document server 200

from

Creates a,

Therefore, another user can just decrypt the encrypted document stored by the user.

Thus, a large number of users can securely and efficiently search for encrypted documents.

On the other hand, the user management apparatus 100 and the document server 200 described above can be implemented in a module, respectively, in the multi-party search system. For example, the user management apparatus 100 may be a user manager, and the document server 200 may be a document manager.

In addition, the above-described encrypted data storage unit 220 of FIG. 3 includes a cache, a read only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), and a flash memory (Flash memory). Or a volatile memory device such as a random access memory (RAM) or a storage medium such as a hard disk drive (HDD) or a CD-ROM, but is not limited thereto. .

And each component shown in Figures 2 to 4 may be composed of a kind of 'module'. The term 'module' refers to a hardware component such as software or a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), and the module performs certain roles. However, modules are not meant to be limited to software or hardware. A module may be configured to reside on an addressable storage medium and may be configured to execute one or more processors. The functionality provided by the components and modules may be combined into a smaller number of components and modules or further separated into additional components and modules.

In addition, the above description of the present invention is intended for illustration, and those skilled in the art may understand that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. There will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

And the scope of the present invention is represented by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. Should be.

100: user management device 110: user list management unit
120: key generation unit 200: document server
210: user list management unit 220: encrypted data storage unit
230: key generation unit 240: data search unit
300: user terminal 310: identification information management request unit
320: data encryption unit 330: query generation unit
340: data decoder

Claims (17)

In the multiparty retrieval system,
In response to a user registration request, issuing a first private key to a user terminal of the user who requested the user registration, and providing a second secret key generated to include the first private key and identification information of the user to a document manager; User management and
Using the random number received from the user terminal and the second secret key, the first generation key used to generate the document encryption key for encrypting the document and the keyword index generation key for encrypting the keyword for the document is used. Generating a second generation key to be provided to the user terminal and storing the encrypted document and the encrypted keyword received from the user terminal;
The encrypted document is encrypted in the user terminal by a document encryption key generated based on the first generation key, and the encrypted keyword is generated by the keyword index generation key generated based on the second generation key. Multi-party retrieval system that is encrypted in the user terminal.
The method of claim 1,
The user terminal generates a query value including the keyword, the identification information of the user, and the first secret key of the user terminal according to a user's keyword input, and transmits the query value to the document manager, and receives the encrypted message received from the document manager. A multiparty retrieval system for decrypting a document.
The method of claim 2,
When the user is a user registered in the user list, the document manager calculates a keyword index generation key based on the query value and the second secret key of the user, and encrypts the corresponding keyword index generation key. Retrieving a document, and transmitting the encrypted document and a first generation key for the encrypted document to the user terminal.
The method of claim 3, wherein
The user terminal calculates a document encryption key for the encrypted document from the first generation key received from the document management unit, and decrypts the encrypted document based on the calculated document encryption key. .
The method of claim 3, wherein
The document management unit,
A user list manager which manages the second secret key generated to include the identification information of the user who has requested the user registration and the first secret key for each user;
A key generation unit generating a first generation key used for generating the document encryption key and a second generation key used for generating the keyword index generation key using the random number received from the user terminal and the second secret key ,
An encrypted data storage unit for storing the encrypted document and the encrypted keyword;
The keyword index generation key is calculated based on the query value and the second secret key of the user, and an encrypted document corresponding to the calculated keyword index generation key is searched for. And a data retrieval unit for transmitting the first generation key to the user terminal.
The method of claim 5, wherein
The user list management unit,
And removing the identification information of the user who requested to withdraw the user and the second secret key of the user who requested to withdraw the user from the user list.
The method of claim 3, wherein
The user terminal,
A data encryption unit generating the document encryption key to encrypt a document to be stored in the document management unit, and generating the keyword index generation key to encrypt a keyword for the document;
A query generator configured to generate the query value including the keyword, identification information of the user, and a first secret key of the user terminal according to a keyword input of the user;
And a data decryption unit for calculating a document encryption key for the encrypted document from the first generation key received from the document manager, and for decrypting the encrypted document based on the calculated document encryption key.
The method of claim 1,
The user management unit,
A user list manager for managing identification information of a user who has requested the user registration as a user list;
Generating the second secret key generated to include the first secret key to be issued to the user terminal of the user who requested the user registration and the first secret key to be provided to the document manager using the secret key of the user manager. Multi-party retrieval system including a key generation unit.
In the multiparty search method,
In response to a user registration request, a user management device issues a first secret key to a user terminal of a user who has requested the user registration, and documents a second secret key generated to include the first secret key and identification information of the user. Providing the server,
A first generation key used to generate a document encryption key for encrypting a document and a keyword index generation key for encrypting a keyword for the document using the random number received from the user terminal and the second secret key by the document server Generating and providing a second generation key used for generation of the terminal to the user terminal; and
And receiving, by the document server, a document encrypted using the document encryption key and a keyword encrypted using the keyword index generation key from the user terminal.
The document encryption key is generated based on the first generation key, and the keyword index generation key is generated based on the second generation key.
Multiparty search method.
The method of claim 9,
If the document server is a user registered in the user list, the document server calculates a keyword index generation key based on the query value received from the user terminal and the second secret key of the user, and calculates the keyword index generation key. Retrieving an encrypted document corresponding to and transmitting the encrypted document and a first generation key for the encrypted document to the user terminal.
The method of claim 10,
And the user terminal generates the query value including the keyword, identification information of the user, and a first secret key of the user terminal according to a user's keyword input.
The method of claim 10,
The user terminal calculates a document encryption key for the encrypted document from the first generation key received from the document server, and decrypts the encrypted document based on the calculated document encryption key. .
The method of claim 9,
And removing, by the document server, identification information of a user who has requested to withdraw from the user and a second secret key of the user who has requested to withdraw from the user from the user list.
In the multiparty retrieval system,
In response to a user registration request, issuing a first secret key to a user terminal of the user who requested the user registration, and providing a document server with a second secret key generated to include the first secret key and identification information of the user; User management device,
A user terminal generating a document encryption key to encrypt a document to be stored in the document server, generating a keyword index generation key to encrypt a keyword for the document, and transmitting the encrypted document and the encrypted keyword to the document server. And
The user terminal is generated by using the random number received from the user terminal and the second secret key to generate a first generation key used to generate the document encryption key and a second generation key used to generate the keyword index generation key. And providing a document server for storing the encrypted document and the encrypted keyword received from the user terminal,
And the user terminal generates the document encryption key based on the first generation key, and generates the keyword index generation key based on the second generation key.
The method of claim 14,
The user terminal generates a query value including the keyword, the identification information of the user, and the first secret key of the user terminal according to a keyword input of the user, transmits the query value to the document server, and receives the encrypted message received from the document server. A multiparty retrieval system for decrypting a document.
The method of claim 15,
When the user is a user registered in the user list, the document server calculates a keyword index generation key based on the query value and the second secret key of the user, and encrypts the corresponding keyword index generation key. Retrieving a document, and transmitting the encrypted document and a first generation key for the encrypted document to the user terminal.
17. The method of claim 16,
And the user terminal calculates a document encryption key for the encrypted document from the first generation key received from the document server, and decrypts the encrypted document based on the calculated document encryption key. .

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