KR102544084B1 - Secure instant messaging method and attaratus thereof - Google Patents

Abstract

A secure instant messaging method and apparatus are disclosed. A secure instant messaging method performed in an administrator's device according to an embodiment includes generating a first emergency key corresponding to a space private key and storing the first emergency key in a server, and recovering the space private key from the server to a first user's account. Obtaining a first emergency key corresponding to , Transmitting an exchange key to a device of a first user logged in with an account of the first user, Obtaining a user private key of the first user based on the exchange key. , and recovering the space private key by decrypting the obtained first emergency key with the user private key of the first user.

Description

Secure instant messaging method and apparatus {SECURE INSTANT MESSAGING METHOD AND ATTARATUS THEREOF}

The embodiments below relate to secure instant messaging methods and apparatus.

An instant messaging service or instant messenger is a messenger service in which two or more users transmit and receive text, pictures, voices, etc. in real time through a network. Since the instant messaging service passes through a messaging server for data communication between users, communication data may be stored in the server. This has a security vulnerability in that data leakage and alteration are possible due to hacking of the server. Accordingly, an encryption technology for security, such as data leakage prevention, should be applied in a data communication process using an instant messaging service.

End to End Encryption (E2EE) is an encryption method that transmits a message in an encrypted state in all processes from the sender to the receiver. It is also called end-to-end encryption. When end-to-end encryption is used, only the sender and receiver of the message can see the contents, and the server in the middle cannot see the contents, so it is a technology for protecting data transmitted and received through instant messaging services. are being developed

The embodiment may provide an instant messaging service with enhanced security for preventing data transmitted and received through a server from being exposed to a third party other than the data sender and receiver.

The embodiment may provide a technique for safely storing and maintaining a key used to recover a user key for encrypting information about a user in an instant messaging service.

However, the technical challenges are not limited to the above-described technical challenges, and other technical challenges may exist.

A secure instant messaging method performed in an administrator's device according to one side includes a first emergency key corresponding to a space private key - the first emergency key is at least one obtained by encrypting the space private key with a user public key of at least one user. generating and storing on a server - including the ciphertext; obtaining a first emergency key corresponding to an account of a first user from the server in order to recover the space private key; transmitting an exchange key to a device of the first user logged in with an account of the first user; obtaining a user private key of the first user based on the exchange key; and recovering the space private key by decrypting the obtained first emergency key with a user private key of the first user.

The manager and the at least one user may be included in a space provided by the secure instant messaging service, wherein the space is a unit including at least one chat room and at least one user.

The space private key may be generated as an asymmetric key corresponding to the space in the device of the manager who manages the space.

The obtaining of the user private key of the first user may include receiving a first cipher text obtained by encrypting the user private key of the first user with the exchange key from a device of the first user; and obtaining a user private key of the first user by decrypting the first ciphertext using the exchange key.

The obtaining of the user private key of the first user may include requesting authentication of the administrator from a device of the first user; and obtaining a user private key of the first user based on the administrator's authentication.

A secure instant messaging method performed in a server according to one aspect includes receiving, from a manager's device, at least one first emergency key obtained by encrypting a space private key with a user public key of at least one user; storing the received at least one first emergency key corresponding to each account of the at least one user; providing information about the account of the at least one user corresponding to the at least one first emergency key to the manager's device in response to a request for recovery of the space private key received from the manager's device; and transmitting a first emergency key stored in correspondence with the account of the first user to the device of the manager in response to an input for selecting an account of the first user from among the accounts of the at least one user based on the information. includes

According to one aspect, a secure instant messaging method performed in an administrator's device includes generating a second ciphertext obtained by encrypting a space private key with a first encryption key and storing the second ciphertext in a server; In order to recover the space private key, a second emergency key from the server—the second emergency key includes at least one cipher text obtained by encrypting the first encryption key with a user public key of at least one user—and the first 2 obtaining ciphertext; transmitting an exchange key to a device of a second user logged in with an account of the second user corresponding to the second emergency key; obtaining a user private key of the second user based on the exchange key; and recovering the space private key based on the first encryption key and the second ciphertext obtained by decrypting the second emergency key with the user private key of the second user.

The manager and the at least one user may be included in a space provided by the secure instant messaging service, wherein the space is a unit including at least one chat room and at least one user.

The space private key may be generated as an asymmetric key corresponding to the space in the device of the manager who manages the space.

The obtaining of the user private key of the second user may include receiving third cipher text obtained by encrypting the user private key of the second user with the exchange key from a device of the second user; and obtaining a user private key of the second user by decrypting the third ciphertext using the exchange key.

The obtaining of the user private key of the second user may include requesting authentication of the administrator from a device of the second user; and obtaining a user private key of the second user based on the administrator's authentication.

The recovering of the space private key may include recovering the space private key by decrypting the second ciphertext using the first encryption key.

A secure instant messaging method performed in a server according to one aspect includes storing a second cipher text obtained by encrypting a space private key received from a manager's device with a first encryption key; storing at least one second emergency key obtained by encrypting the first encryption key with the user public key of at least one user in correspondence with each account of the at least one user; providing information about the account of the user corresponding to the second passphrase and the second emergency key to the device of the administrator in response to a request for recovery of the space private key received from the device of the administrator; and in response to an input of the manager selecting an account of a second user from among the accounts of the at least one user based on the information, the second emergency key stored in correspondence to the account of the second user is stored on the device of the manager. It includes sending to

The storing of the at least one second emergency key corresponding to each account of the at least one user may include at least one encryption key obtained by encrypting the first encryption key with the user public key of the at least one user from the manager's device. Receiving a second emergency key; and receiving at least one second emergency key obtained by encrypting the first encryption key with the user public key of the at least one user from a device of a third user who has obtained the first encryption key from the manager's device. may contain at least one.

According to one aspect, a secure instant messaging method performed on a device of a third user includes a second emergency key corresponding to an account of the third user obtained by encrypting a first encryption key with a user public key of the third user, from a device of an administrator. obtaining; obtaining the first encryption key by decrypting the obtained second emergency key with a user private key of the third user; and generating at least one second emergency key obtained by encrypting the first encryption key with a user public key of at least one other user and storing the second emergency key in a server.

An administrator's device according to one side generates a first emergency key corresponding to a space private key, wherein the first emergency key includes at least one cipher text obtained by encrypting the space private key with a user public key of at least one user. and store it in a server, and in order to recover the space private key, a first emergency key corresponding to the account of the first user is obtained from the server, and the device of the first user logged in with the account of the first user Transmitting an exchange key, obtaining a user private key of the first user based on the exchange key, and recovering the space private key by decrypting the obtained first emergency key with the user private key of the first user. , contains at least one processor.

The server according to one side receives at least one first emergency key obtained by encrypting a space private key with a user public key of at least one user, from a device of an administrator, and converts the received at least one first emergency key to the at least one user public key. Information about the at least one user's account corresponding to the at least one first emergency key stored in correspondence with each user's account and in response to a request for recovery of the space private key received from the manager's device is provided to the manager's device, and in response to an input for selecting an account of the first user from among the accounts of the at least one user based on the information, a first emergency key stored in correspondence to the account of the first user is provided. and at least one processor for transmitting to the manager's device.

An administrator's device according to one side generates and stores a second ciphertext obtained by encrypting a space private key with a first encryption key in a server, and in order to recover the space private key, the second emergency key-the second emergency key is generated from the server. The key includes at least one cipher text obtained by encrypting the first encryption key with a user public key of at least one user - and obtains the second cipher text, and logs in with an account of a second user corresponding to the second emergency key. An exchange key is transmitted to the device of the second user, the user private key of the second user is obtained based on the exchange key, and the second emergency key is decrypted and obtained with the user private key of the second user. and at least one processor for recovering the space private key based on the first encryption key and the second cipher text.

The server according to one side stores second cipher text obtained by encrypting the space private key received from the manager's device with the first encryption key, and stores the second ciphertext obtained by encrypting the first encryption key with the user public key of at least one user. An emergency key is stored in correspondence with each of the at least one user's account, and in response to a request for recovery of the space private key received from the manager's device, the second ciphertext and the user corresponding to the second emergency key Provides account-related information to the manager's device, and responds to the manager's input for selecting the second user's account from among the at least one user's account based on the information, and responds to the second user's account. and at least one processor for transmitting the stored second emergency key to the manager's device.

A device of a third user according to one side obtains, from a device of an administrator, a second emergency key corresponding to an account of a third user in which a first encryption key is encrypted with a user public key of the third user, and the obtained 2 Decrypting the emergency key with the user private key of the third user to obtain the first encryption key, and generating at least one second emergency key obtained by encrypting the first encryption key with the user public key of at least one other user Stored in a server, includes at least one processor.

The embodiment may provide an instant messaging service with enhanced security by transmitting and receiving data between devices through a server in an end-to-end encryption method.

The embodiment encrypts data so that it is transmitted, received, and stored through a server, thereby preventing access to the data by a third party including the server.

The embodiment safely stores and maintains a key used to recover a user key for encrypting information about a user in an instant messaging service, thereby preventing loss of information about a user, such as messages transmitted and received through a chat room provided by an instant messaging service. can be prevented, and a technology that can be safely restored to the user's device can be provided.

1 is an exemplary diagram of a secure instant messaging system configuration according to one embodiment.
2 is a diagram for explaining a first emergency key for recovery of a space private key according to an embodiment.
3 is an operation flowchart for recovering a space private key based on a first emergency key according to an embodiment.
4 is an operation flowchart of a secure instant messaging method performed in a manager's device according to an embodiment.
5 is an operation flowchart of a secure instant messaging method performed in a server according to an embodiment.
6 is a diagram for explaining a second emergency key for recovery of a space private key according to an embodiment.
7 is an operation flowchart for recovering a space private key based on a second emergency key according to an embodiment.
8 is an operation flowchart of a secure instant messaging method performed in a manager's device according to an embodiment.
9 is an operation flowchart of a secure instant messaging method performed in a server according to an embodiment.
10 is an operation flowchart of a secure instant messaging method performed in a device of a third user according to an embodiment.
11 is an exemplary diagram of a configuration of a device according to an embodiment.

Specific structural or functional descriptions of the embodiments are disclosed for illustrative purposes only, and may be changed and implemented in various forms. Therefore, the form actually implemented is not limited only to the specific embodiments disclosed, and the scope of the present specification includes changes, equivalents, or substitutes included in the technical idea described in the embodiments.

Although terms such as first or second may be used to describe various components, such terms should only be construed for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element.

It should be understood that when an element is referred to as being “connected” to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but one or more other features or numbers, It should be understood that the presence or addition of steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this specification, it should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted.

1 is an exemplary diagram of a secure instant messaging system configuration according to one embodiment.

Referring to FIG. 1 , a secure instant messaging system according to an embodiment may include a user's device 110 , a server 120 and a database 130 . The database 130 is a storage space for storing data accessible from the server 120. Data stored in the database 130 can be understood as data stored in the server 120, and data stored in the server 120 This may be understood as storing data in database 130 via server 120 . The database 130 may be included in the server 120 or may exist outside the server, but for convenience of explanation, the database 130 will be described as being included in the server 120 as an example.

A secure instant messaging system according to an embodiment is a system that provides a secure instant messaging service, and can provide a service capable of transmitting and receiving text, photos, media, and the like between service users. Hereinafter, the secure instant messaging system may be briefly referred to as 'system'.

An instant messaging service is a messenger service in which a user transmits and receives text, picture, voice, etc. through a network in real time. The instant messaging service may be installed in a user's terminal in the form of an application or program to provide a messenger service to the user. The instant messaging service may provide a chat room through which a message including data such as text may be transmitted/received with a user designated counterpart, and the message may be provided to the user by displaying data transmitted/received through the chat room. One or more users may be included in one chat room, and it is also possible to send and receive messages by creating a chat room with only one user. The user(s) included in the chat room may share contents of messages such as texts and photos transmitted and received in the chat room. The instant messaging service may create an account for each user according to a subscription procedure, and may manage chat rooms and messages corresponding to the user's account. The user may send and receive messages with the user(s) subscribed to the instant messaging service through a chat room using a device logged in with an account created by subscribing to the instant messaging service. Hereinafter, the user's device 110 may refer to a device logged in with an account of a user subscribed to an instant messaging service. Hereinafter, a user using an instant messaging service may be understood to mean a user who is a natural person or an account subscribed to an instant messaging service according to circumstances.

According to an embodiment, an instant messaging service may provide a 'space' unit including at least one chat room and at least one user. For example, a space may be created corresponding to a specific company, and in this case, the space may include accounts corresponding to members of the company. Members of a company corresponding to the created space may share information by creating a chat room in the space using an account subscribed to the instant messaging service. A space can be opened by any user, and at least one administrator can be designated. For example, a user who created a space (hereinafter referred to as a space creator) may designate at least one of users included in the space as a space manager. The space manager may obtain information of user(s) included in the space and/or information of chat room(s) included in the space. In addition to this, space administrators can have authority for space management.

The secure instant messaging service is an instant messaging service with enhanced security, and may include an instant messaging service in which data is encrypted and transmitted/received using an end-to-end encryption method.

Data transmitted/received and/or stored in the system may correspond to data encrypted for security. More specifically, data transmitted, received, and/or stored via a secure instant messaging system may be encrypted in an end-to-end encryption manner such that it can be decrypted by designated recipients. Designated recipients may include users who are designated as targets for receiving data in various ways, for example, may be designated as recipients by the sender, may be automatically designated as recipients belonging to a specific group, and secure instant messaging In the service, the user(s) included in the chat room in which data is sent may be designated as the receiver. Since the data transmitted and received by the system through the server 120 and/or the data stored in the server are encrypted data through an end-to-end encryption method, the server 120 and a third party accessing the server 120 refer to the original data. A secure instant messaging service with enhanced security can be provided because it cannot be altered or forged/falsified.

The server 120 and the user's device 110 may transmit and receive data over a network. For example, the server 120 and the user's device 110 may transmit and receive data through a network formed by an application related to a secure instant messaging service. Data communication between the server 120 and the user's device 110 may be performed based on network encryption. For example, data communication may be performed between the server 120 and the user's device 110 as a client according to Secure Sockets Layer (SSL). Data transmitted/received between the server 120 and the user's device 110 may be encrypted with a symmetric key between the server 120 and the user's device 110 before being transmitted/received. The symmetric key between the server 120 and the user's device 110 may be encrypted with a public key distributed by the server to the client and transmitted to the server 120, and the server 120 may correspond to the public key. You can verify the symmetric key by decrypting it with the private key. In a communication session, the server and the client can maintain security by encrypting data with a symmetric key and transmitting and receiving data.

A process of transmitting and receiving data between a server and a user's device described below may include a process of transmitting and receiving data encrypted by a network encryption method.

Database 130 may store data relating to secure instant messaging services. Data related to the secure instant messaging service is data managed by the server to provide the secure instant messaging service, for example, identification information of users who have subscribed to the secure instant messaging service, chat room information corresponding to the user, information transmitted and received through the chat room. It may include message information and the like.

Data related to the secure instant messaging service may be stored in the database 130 by the server 120, and may be stored in different databases according to types of data.

The database 130 may store public keys of users subscribed to the secure instant messaging service. The user's public key may be stored in the database 130 corresponding to the user's account. The database 130 may store public keys of users corresponding to accounts of a plurality of users subscribed to the secure instant messaging service, and each of the public keys may be stored corresponding to the user's account. For example, a user's public key may be indexed to the user's account and stored in database 130 .

The user's public key may be generated in the user's device in correspondence with the user's account, and a private key capable of decrypting data encrypted with the public key may be generated together. Hereinafter, a pair of a public key corresponding to a user's account and a private key corresponding thereto may be referred to as a user key. In other words, the user key corresponding to the user's account is an asymmetric key and includes a public key as an encryption key and a private key as a decryption key. Hereinafter, a public key among user keys may be referred to as a user public key, and a private key among user keys may be referred to as a user private key.

The user's device 110 may generate a user key corresponding to the user's account, store the user private key in the device 110 , and transmit the user public key to the server 120 . The server 120 may receive a user public key from the user's device 110 and store it in the database 130 . In other words, among the user keys corresponding to the user's account generated in the user's device 110, the user public key is stored in the database 130 by the server 120, and the user private key is stored in the user's device 110. can be stored Since the server does not hold the user's private key, the server cannot decrypt data encrypted with the user's public key. The user public key may also be stored in the user's device 110 .

The database 130 may store a space public key corresponding to a space created in the secure instant messaging service. The space public key can be generated on the device of the space creator when the space is opened, and a space private key capable of decrypting data encrypted with the space public key can be generated together. Hereinafter, a pair of a space public key corresponding to a space and a space private key corresponding thereto may be referred to as a space encryption key. In other words, the space encryption key corresponding to the space is an asymmetric key and includes a space public key as an encryption key and a space private key as a decryption key.

The device of the space establisher may generate a space encryption key corresponding to the space, store the space private key in the device of the space establisher, and transmit the space public key to the server 120 . The server 120 may receive the space public key and store it in the database 130 . In other words, the space public key corresponding to the space account may be stored in the database 130 by the server 120, and the space private key may be stored in the device of the space establisher. Since the server does not have the space private key, the server cannot decrypt data encrypted with the space public key. The space public key can also be stored on the space creator's device.

According to an embodiment, the space creator may encrypt and transmit the space private key to the space manager's device in a decryptable manner in the space manager's device, and the space private key may be stored in the space manager's device. Hereinafter, a space manager's device may be understood as a device that holds a space private key and is logged into a space manager's account, and may be briefly referred to as a 'manager's device'.

The database 130 may store encrypted symmetric keys of chat rooms generated in the secure instant messaging service. The encrypted symmetric key of the chat room may include a symmetric key encrypted with a user public key of each of the chat room participants. The encrypted symmetric key of the chat room may be stored corresponding to the user's account. For example, a symmetric key of a chat room encrypted with a user public key corresponding to the first user's account may be indexed and stored with the first user's account, or indexed with a user public key corresponding to the user's account and stored. . The encrypted symmetric key of the chat room may be stored in correspondence with identification information of the chat room corresponding to the account of the user. For example, when a first user participates in a first chat room, identification information of the first chat room may be stored corresponding to an account of the first user, and corresponding to the first identification information of the first chat room, the first chat room may be stored. A symmetric key of the first chat room encrypted with user public keys of users participating in the chat room may be stored. More specifically, when the first user and the second user are participating in the first chat room, the symmetric key of the first chat room encrypted with the user public key of the first user and the second user corresponding to the identification information of the first chat room. A symmetric key of the first chat room encrypted with the user public key may be stored. Since the private key among the user keys is not stored in the server, the server cannot decrypt the symmetric key of the chat room encrypted with the user public key corresponding to the user account. By encrypting and storing the symmetric key of the chat room in the server, it is possible to prevent chat room information from being exposed to a third party.

According to an embodiment, a symmetric key of a chat room encrypted with a user public key may include information about a user's account corresponding to the user public key. In other words, the symmetric key of the encrypted chat room may include information for identifying a user corresponding to the user public key used for encryption. For example, when the symmetric key of the first chat room is encrypted with the user public key of the first user to generate the first ciphertext, the first ciphertext indicates that the ciphertext is encrypted with the user public key of the first user. information may be included. Also, for example, when the symmetric key of the first chat room is encrypted with the user public key of the first user to generate the first ciphertext, the first ciphertext may be stored in the server in correspondence with the account of the first user.

The database 130 may store messages encrypted with the symmetric key of the chat room. Messages transmitted and received through the chat room may be encrypted with a symmetric key of the chat room and transmitted/received between users, and the encrypted messages may be stored in a server corresponding to the chat room. Since the server stores the cipher text encrypted with the symmetric key of the chat room, the server cannot decrypt the message encrypted with the symmetric key of the chat room because it cannot know the symmetric key of the chat room. Message information can be prevented from being exposed to a third party by encrypting the message with the symmetric key of the chat room and storing it in the server.

According to an embodiment, the database 130 may store a user key encrypted with a space public key. The user key encrypted with the space public key is used to recover the user key to the user's device when the user key corresponding to the user's account is unavailable, such as when the device storing the user key corresponding to the user's account is lost. can be used For example, a space administrator's device holding a space private key can decrypt a user key corresponding to a specific user's account with the space private key and transmit it to a new device logged in with the user's account. When the user key is transferred to a new device, it can be encrypted and transferred so as not to be exposed to third parties.

According to an embodiment, the database 130 may store a symmetric key of a chat room encrypted with a space public key. As described above, the database 130 may store the encrypted symmetric key of the chat room, and the encrypted symmetric key of the chat room may include a symmetric key encrypted with the public key of each user of the chat room participants. The symmetric key may further include a symmetric key encrypted with the space public key. In other words, corresponding to a specific chat room, a symmetric key encrypted with a user public key of each chat room participant and a symmetric key encrypted with a space public key may be stored. Also, as described above, the encrypted symmetric key(s) corresponding to a specific chat room may be stored corresponding to each of the chat room participants' accounts.

The space private key may correspond to a decryption key of information about a space encrypted with a space public key (eg, a user key of a user included in the space and a symmetric key of a chat room included in the space). As described above, the space private key may be stored in the space manager's device, and the space private key may be lost due to the loss of the space manager's device or memory initialization of the space manager's device.

In case the space private key is lost, an emergency key capable of recovering the space private key may be stored in the database 130 according to an embodiment. The emergency key may include at least one of a first emergency key and a second emergency key. A secure instant messaging method for generating and storing an emergency key for recovery of a space private key will be described in detail below.

2 is a diagram for explaining a first emergency key for recovery of a space private key according to an embodiment.

는 사용자 k의 유저 퍼블릭 키, SP_d는 스페이스 프라이빗 키, ekey₁는 제1 비상키, E_key는 키 key를 이용한 암호화 함수를 의미할 수 있다.Referring to Figure 2,

is the user public key of user k, SP _d is the space private key, ekey ₁ is the first emergency key, and E _key is the encryption function using the key key.

를 생성(230)할 수 있다. 다시 말해, 제1 비상키(ekey₁)는 스페이스 프라이빗 키 SP_d를 n개의 사용자의 계정 {user_k | k = 1, 2, …, n} 각각에 대응하는 유저 퍼블릭 키

로 암호화한 n개의 암호문

을 포함할 수 있다. n은 1 이상의 임의의 자연수에 해당할 수 있다. 제1 비상키에 포함된 스페이스 프라이빗 키 SP_d를 사용자 k의 유저 퍼블릭 키

로 암호화한 암호문

은 사용자 k에 대응하는 제1 비상키 혹은 user_k_ekey₁로 지칭될 수 있다. According to an embodiment, the administrator's device is the first emergency key corresponding to the space private key.

Can generate (230). In other words, the first emergency key (ekey ₁ ) uses the space private key SP _d for n user accounts {user _k | k = 1, 2, … , n} corresponding user public key

n ciphertexts encrypted with

can include n may correspond to any natural number greater than or equal to 1. The space private key SP _d included in the first emergency key is the user public key of user k.

ciphertext encrypted with

may be referred to as a first emergency key corresponding to user k or user _{k_ekey 1} .

According to one embodiment, as described above, the manager's device is a device logged into the space manager's account and may correspond to a device holding a space private key. The user public key of at least one user encrypting the space private key may correspond to the user public key of at least one user included in the same space as the manager. In other words, an administrator and at least one user may be included in a space provided by a secure instant messaging service. As described above, a space may correspond to a unit including at least one chat room and at least one user.

를 관리자의 디바이스에 전송(220)할 수 있다. 상술한 바와 같이, 서버는 사용자의 계정에 대응하여, 해당 사용자의 유저 퍼블릭 키를 저장할 수 있다. 서버는 스페이스에 포함된 사용자의 계정들 중 미리 정해진 n개의 사용자의 계정에 대응하는 n개의 유저 퍼블릭 키

를 관리자의 디바이스에 전송(220)할 수 있으며, 관리자의 디바이스는 서버로부터 스페이스에 포함된 n개의 사용자의 계정에 대응하는 유저 퍼블릭 키

를 획득할 수 있다.According to an embodiment, the manager's device may request (210) the user public key of at least one user included in the space to the server in order to generate the first emergency key. The server responds to the request received from the manager's device, and the user public key of at least one user included in the space.

may be transmitted to the manager's device (220). As described above, the server may store the user public key of the corresponding user in correspondence with the user's account. The server provides n user public keys corresponding to predetermined n user accounts among user accounts included in the space.

may be transmitted to the manager's device (220), and the manager's device may send a user public key corresponding to the accounts of n users included in the space from the server.

can be obtained.

According to an embodiment, the server may select some of the users included in the space and transmit the user public key of the selected user to the manager's device. For example, the server may randomly select a predetermined number of users from among users included in the space. As another example, a predetermined number of users may be selected based on the activity levels of the users included in the space. The degree of activity in the space may be determined based on at least one of, for example, the number of messages transmitted and received using a chat room included in the space, the number of logins, and the number of accesses to the space.

)로 스페이스 프라이빗 키를 암호화하여 생성된 제1 비상키(

)는 제1 사용자의 계정(user₁)에 대응하여 저장될 수 있고, 제2 사용자의 유저 퍼블릭 키(

)로 스페이스 프라이빗 키를 암호화하여 생성된 제1 비상키(

)는 제2 사용자의 계정(user₂)에 대응하여 저장될 수 있다.According to an embodiment, the manager's device may generate (230) a first emergency key including n cipher texts by encrypting the space private key with each of the user public keys of n users obtained from the server. The manager's device may transmit (240) the generated first emergency key to the server, and the server may store (250) the first emergency key corresponding to the user's account. For example, the user public key of the first user (

) The first emergency key generated by encrypting the space private key (

) may be stored in correspondence with the account of the first user (user ₁ ), and the user public key of the second user (

) The first emergency key generated by encrypting the space private key (

) may be stored in correspondence with the account of the second user (user ₂ ).

According to an embodiment, the first emergency key may be sequentially generated and stored in the server. For example, a predetermined number of first emergency keys may be generated at regular intervals and stored in a server, and as a new user's account is included in the space, a first emergency key corresponding to the new user's account may be generated.

According to an embodiment, the location where the first emergency key is stored can be obtained from the manager's device, and the manager's device can request the first emergency key from the server based on the location where the first emergency key is stored. A device of another user may not be able to obtain a location where the first emergency key is stored, and thus may not be able to request the first emergency key from the server.

3 is an operation flowchart for recovering a space private key based on a first emergency key according to an embodiment.

는 사용자 k의 유저 퍼블릭 키,

는 사용자 k의 유저 프라이빗 키, SP_d는 스페이스 프라이빗 키, EX는 교환 키, c₁은 제1 암호문, ekey₁는 제1 비상키, user_k_ekey₁는 사용자 k의 유저 퍼블릭 키

로 스페이스 프라이빗 키 SP_d를 암호화하여 생성된 사용자 k에 대응하는 제1 비상키, E_key는 키 key를 이용한 암호화 함수, D_key는 키 key를 이용한 복호화 함수를 의미할 수 있다.Referring to FIG. 3, user _k is an account of user k,

is the user public key of user k,

is the user private key of user k, SP _d is the space private key, EX is the exchange key, c ₁ is the first passphrase, ekey ₁ is the first emergency key, user _{k_ekey 1} is the user public key of user k

A first emergency key corresponding to user k generated by encrypting the space private key SP _d with , _key E may denote an encryption function using the key key, and _key D may denote a decryption function using the key key.

According to an embodiment, when the manager's device loses the space private key, it may request 310 to restore the space private key to the server. In response to the space private key recovery request, the server responds to information about at least one user's account corresponding to the first emergency key {user ₁ , user ₂ , . . . , user _n } may be provided to the manager's device (320). The information about the user account corresponding to the first emergency key may include a list of user accounts corresponding to the user public key used to generate the first emergency key. For example, when the first non-emergency key includes ciphertext generated by encryption with the user public key of the first user and ciphertext generated by encryption with the user public key of the second user, the server stores the account and/or the password of the first user. 2 The list including the user's account may be transmitted to the manager's device as information about the user's account corresponding to the first emergency key.

According to an embodiment, the administrator's device selects one of the provided user accounts (eg, user ₁ ) and requests the server for a first emergency key corresponding to the selected user's account (330) can do. Hereinafter, it will be described as an example in which the administrator's device selects the account of the first user and requests the first emergency key corresponding to the account of the first user.

Upon receiving the request for the first emergency key corresponding to the first user's account from the manager's device, the server may provide (340) the first emergency key user _{1_ekey 1} corresponding to the first user's account to the manager's device. there is.

The manager's device may transmit (350) the exchange key to the first user's device through the server. The first user's device may refer to a device logged into the first user's account. For example, the administrator's device may request the server to transmit an exchange key to the user's account corresponding to the first emergency key, and the server may transmit the exchange key to the first user's device.

According to an embodiment, the exchange key is a key for encrypting a user private key, and the exchange key may correspond to a symmetric key or an asymmetric key. When the exchange key is an asymmetric key, the exchange key transmitted to the device of the first user may correspond to an encryption key of the exchange key. Transmitting the exchange key (350) may include requesting the first user's user private key from the first user's device. In other words, sending the exchange key may include requesting the user's private key.

According to an embodiment, when the manager's device requests the server for the first emergency key corresponding to the account of the first user, the exchange key may be transmitted to the server along with the request. In other words, the operation 330 of requesting the first emergency key corresponding to the account of the first user of the manager's device may include operation 350 of transmitting the exchange key to the device of the first user through the server. .

을 생성(360)할 수 있으며, 제1 암호문은 서버를 통해 관리자의 디바이스로 전달(370)될 수 있다.According to an embodiment, the device of the first user encrypts the user private key of the first user with the received exchange key, and the first ciphertext

It can generate (360), and the first password text can be delivered to the manager's device through the server (370).

According to an embodiment, the device of the first user may perform an operation of authenticating the device of the administrator before transmitting the first password text. For example, the first user's device can check whether the manager's device that sent the exchange key is an account designated as the manager of the space that includes the first user's account, and if it is confirmed as the account designated as the manager, 1 ciphertext can be transmitted.

According to an embodiment, the manager's device receiving the first encrypted text from the first user's device may decrypt the first encrypted text with an exchange key to obtain a user private key of the first user (380). If the exchange key is an asymmetric key, the administrator's device can decrypt the ciphertext using the decryption key of the exchange key. The manager's device may obtain the space private key by decrypting the first emergency key using the obtained user private key of the first user (390). In other words, the lost space private key in the manager's device can be restored based on the first emergency key, and the restored space private key can be stored in the manager's device.

4 is an operation flowchart of a secure instant messaging method performed in a manager's device according to an embodiment.

Referring to FIG. 4 , in the secure instant messaging method performed on the administrator's device according to an embodiment, a first emergency key corresponding to a space private key is generated and stored in a server (410), and the space private key is recovered. To do this, obtaining a first emergency key corresponding to the account of the first user from the server (420), transmitting the exchange key to the device of the first user logged in with the account of the first user (430), the exchange key Based on , it may include obtaining a user private key of the first user (440) and recovering the space private key by decrypting the obtained first emergency key with the user private key of the first user (450). . At least one user and administrator may be included in a space provided by the secure instant messaging service. The at least one user may include a first user.

The secure instant messaging method performed in the manager's device shown in FIG. 4 may correspond to the operations of the manager's device described above with reference to FIGS. 2 and 3 . For example, step 410 may correspond to the operation of the manager's device described above with reference to FIG. 2 , and steps 420 to 450 may correspond to the operation of the manager's device described above with reference to FIG. 3 .

Step 410 according to an embodiment includes generating a first emergency key including at least one cipher text obtained by encrypting a space private key with at least one user public key, and storing the generated first emergency key in a server. steps may be included. In other words, the first emergency key corresponding to the space private key may include at least one cipher text obtained by encrypting the space private key with the user public key of at least one user. At least one user public key may be obtained from a server. For example, the manager's device may request a user public key corresponding to at least one user account included in the space from the server, and the server may provide the manager's device with the user public key of at least one user. .

Step 420 according to an embodiment may be performed when the space private key is lost in the manager's device. The first emergency key may include a first emergency key corresponding to an account of the first user, which is cipher text obtained by encrypting the space private key with the user public key of the first user. The manager's device may request a first emergency key corresponding to the first user's account stored in the server, and may obtain the first emergency key corresponding to the first user's account from the server. As described above, the manager's device can acquire the location where the first emergency key is stored, and can request the first emergency key from the server.

Step 430 according to an embodiment may include transmitting an exchange key for encrypting the user private key of the first user to the device of the first user. As noted above, transmitting 430 the exchange key may include requesting a user private key.

Obtaining a user private key of a first user according to an embodiment (440) includes receiving a first ciphertext obtained by encrypting the user private key of the first user with an exchange key from a device of the first user, and using the exchange key as the first cipher text. Decrypting the ciphertext may include obtaining a user private key of the first user. The device of the first user may generate a first ciphertext obtained by encrypting the user private key of the first user based on the received exchange key, and transmit the first ciphertext to the device of the manager, and the device of the manager may acquire the first ciphertext. In the manager's device, the first ciphertext may be decrypted with an exchange key, and as a result of decryption of the first ciphertext, the user private key of the first user may be obtained.

Obtaining the user private key of the first user according to an embodiment (440) includes requesting an administrator's authentication from the first user's device and acquiring the user private key of the first user based on the administrator's authentication. steps may be included. As described above, the device of the first user may check whether the sender of the request for the user private key is the manager of the space to which the account of the first user belongs, and if the manager is identified, the user private key may be encrypted and transmitted. there is.

If the administrator's authentication fails in step 440 according to an embodiment, the administrator's device may not be able to obtain the first password text.

Step 450 according to an embodiment may include obtaining a space private key by decrypting a first emergency key encrypted with the user public key of the first user using the obtained user private key of the first user. can The manager's device may acquire access rights to the space private key by storing the obtained space private key or storing it in a secure medium accessible from the manager's device.

5 is an operation flowchart of a secure instant messaging method performed in a server according to an embodiment.

Referring to FIG. 5 , a secure instant messaging method performed in a server according to an embodiment includes receiving at least one first emergency key from a manager's device (510), and the received at least one first emergency key. Storing corresponding to each of at least one user's account (520), providing information about the at least one user's account corresponding to the first emergency key to the manager's device (530) and the first user's account It may include a step 540 of transmitting the stored first emergency key corresponding to the manager's device.

The secure instant messaging method performed by the server shown in FIG. 5 may correspond to the operation of the server described above with reference to FIGS. 2 and 3 . For example, steps 510 and 520 may correspond to the operation of the server described above in FIG. 2, and steps 530 and 540 may correspond to the operation of the server described above in FIG. 3 .

Step 510 according to an embodiment may include receiving at least one first emergency key obtained by encrypting a space private key with a user public key of at least one user, from a manager's device. At least one user and administrator may be included in a space provided by the secure instant messaging service. For example, the step 510 of receiving at least one first emergency key from the manager's device may be performed at regular intervals, and the number of first emergency keys received may correspond to a predetermined number. As another example, step 510 of receiving the first emergency key may be performed as it is included in the account of the new user in the space.

Step 520 according to an embodiment stores at least one first emergency key corresponding to each of the at least one user account in order to identify the user account corresponding to the user public key that encrypts the first emergency key. It may correspond to the step of

As described above, the administrator's device can obtain the location where the first emergency key is stored, request the server for the first emergency key, and the server can transmit information about the user's account corresponding to the first emergency key to the administrator. can be delivered to the device of For example, another user's device may not be able to obtain a location where the first emergency key is stored, and thus may not be able to request the first emergency key from the server. As another example, when the server can request the first emergency key without based on the stored location of the first emergency key, the server receives a request for the first emergency key from a user other than the administrator, the first emergency key may not transmit. In other words, the server may operate to transmit the first emergency key in response to the request for the first emergency key received from the device identified as the manager's device.

Step 530 according to an embodiment includes providing information about the account of at least one user corresponding to a first emergency key to the manager's device in response to the space private key recovery request received from the manager's device. steps may be included. Information about at least one user account corresponding to the first emergency key may include a list of user accounts corresponding to the user public key used to generate the first emergency key stored in the server in correspondence with the space.

Step 540 according to an embodiment includes the first user account stored in response to the first user account in response to an input for selecting an account of the first user from among at least one user account based on information about the user account. 1 may include transmitting the emergency key to the manager's device. The input for selecting the account of the first user may correspond to an input received from the manager's device. The administrator's device may select one of the user accounts corresponding to the user key used to generate the first emergency key, based on the user account information provided from the server, and correspond to the user account selected by the server. It is possible to request a first emergency key that The first emergency key corresponding to the account of the selected user may correspond to a space private key encrypted with the user public key of the selected user.

6 is a diagram for explaining a second emergency key for recovery of a space private key according to an embodiment.

는 사용자 k의 유저 퍼블릭 키, SP_d는 스페이스 프라이빗 키, ekey₂는 제2 비상키, E_key는 키 key를 이용한 암호화 함수를 의미할 수 있다.Referring to FIG. 6, AES is a first encryption key,

is the user public key of user k, SP _d is the space private key, ekey ₂ is the second emergency key, and E _key is the encryption function using the key key.

를 생성(610)할 수 있다. 제1 암호화 키는 관리자의 디바이스에서 스페이스 프라이빗 키를 암호화하기 위하여 생성된 암호화 키로, 예를 들어 고급 암호화 표준(Advanced Encryption Standard, AES) 방식에 따라 생성된 대칭 키를 포함할 수 있다. 이하에서, 제1 암호화 키는 암호화 키와 복호화 키가 동일한 대칭 키인 것으로 예를 들어 설명한다.According to one embodiment, the administrator's device encrypts the space private key with the first encryption key, and the second ciphertext

can generate (610). The first encryption key is an encryption key generated to encrypt the space private key in the administrator's device, and may include, for example, a symmetric key generated according to the Advanced Encryption Standard (AES) method. Hereinafter, the first encryption key will be described as an example in which the encryption key and the decryption key are the same symmetric key.

According to one embodiment, the manager's device may transmit 620 the second cipher text to the server to store it, and the server may store the second cipher text in response to the space (630). For example, the location where the second cipher text is stored may be obtained from the manager's device, and the manager's device may request the second cipher text from the server based on the location where the second cipher text is stored. A device of another user may not be able to obtain a location where the second cipher text is stored, and thus may not be able to request the second cipher text from the server.

를 생성(640 혹은 650)할 수 있다. 다시 말해, 제2 비상키(ekey₂)는 제2 암호문을 복호화하기 위한 제1 암호화 키를 n개의 사용자의 계정 {user_k | k = 1, 2, …, n} 각각에 대응하는 유저 퍼블릭 키

로 암호화한 n개의 암호문

을 포함할 수 있다. n은 1 이상의 임의의 자연수에 해당할 수 있다. 제2 비상키에 포함된 제1 암호화 키 AES를 사용자 k의 유저 퍼블릭 키

로 암호화한 암호문

은 사용자 k에 대응하는 제2 비상키 혹은 user_k_ekey₂로 지칭될 수 있다. According to an embodiment, a device of an administrator or a device of a third user included in a space is a second emergency key corresponding to a space private key.

can be created (640 or 650). In other words, the second emergency key (ekey ₂ ) is a first encryption key for decrypting the second cipher text, n user accounts {user _k | k = 1, 2, … , n} corresponding user public key

n ciphertexts encrypted with

can include n may correspond to any natural number greater than or equal to 1. The first encryption key AES included in the second emergency key is the user public key of user k.

ciphertext encrypted with

may be referred to as a second emergency key corresponding to user k or user _{k_ekey 2} .

According to one embodiment, a device of any third user among users included in the space may acquire a first encryption key from a device of a manager. For example, the administrator's device may generate a second emergency key corresponding to the third user by encrypting the first encryption key generated to encrypt the space private key with the user public key of the third user, and The second emergency key corresponding to may be delivered to the third user's device. The device of the third user may obtain the first encryption key by decrypting the second emergency key corresponding to the third user with the user private key of the third user. In other words, the device of the third user may correspond to a device of a user corresponding to any one of users corresponding to the second emergency key generated in the device of the manager.

According to an embodiment, a device of a third user who has obtained the first encryption key may generate a second emergency key by encrypting the device with a user public key of another user included in the space. The second emergency key corresponding to the other user generated in the device of the third user may be transmitted to the server (650). In other words, not only the device of the administrator who generated the first encryption key, but also the device of the third user can transmit (650) the second emergency key generated by encrypting the first encryption key with the user public key of another user to the server. there is. Since the second emergency key can be generated not only from the administrator's device but also from other user's devices included in the space, even when the administrator's activity is small, the second emergency key is generated by the activity of other users included in the space and the server can be stored in

로 제1 암호화 키를 암호화하여 생성된 제2 비상키

는 제1 사용자의 계정 user₁에 대응하여 저장될 수 있고, 제2 사용자의 유저 퍼블릭 키

로 제1 암호화 키를 암호화하여 생성된 제2 비상키

는 제2 사용자의 계정 user₂에 대응하여 저장될 수 있다.According to an embodiment, the server may store the second emergency key corresponding to the user's account (660). For example, the user public key of the first user

The second emergency key generated by encrypting the first encryption key with

may be stored in correspondence to the account user ₁ of the first user, and the user public key of the second user

The second emergency key generated by encrypting the first encryption key with

may be stored in correspondence with the second user's account user ₂ .

According to an embodiment, the second emergency key may be sequentially generated in a manager's device or another user's device included in a space and stored in a server. For example, a certain number of second emergency keys may be generated at regular intervals and stored in a server, and as a new user's account is included in the space, a second emergency key corresponding to the new user's account may be generated.

Although the case where the first encryption key is a symmetric key has been described as an example, the first encryption key may be generated as an asymmetric key. In this case, the second ciphertext is generated by being encrypted with the first encryption key, which is the encryption key, and the second emergency key may be generated by encrypting the decryption key corresponding to the first encryption key with the user public key.

7 is an operation flowchart for recovering a space private key based on a second emergency key according to an embodiment.

는 사용자 k의 유저 퍼블릭 키,

는 사용자 k의 유저 프라이빗 키, SP_d는 스페이스 프라이빗 키, AES는 제1 암호화 키, EX는 교환 키, c₂은 제2 암호문, c₃은 제3 암호문, ekey₂는 제2 비상키, user_k_ekey₂는 사용자 k의 유저 퍼블릭 키

로 제1 암호화 키 AES를 암호화하여 생성된 사용자 k에 대응하는 제2 비상키, E_key는 키 key를 이용한 암호화 함수, D_key는 키 key를 이용한 복호화 함수를 의미할 수 있다.Referring to FIG. 7, user _k is an account of user k,

is the user public key of user k,

is the user private key of user k, SP _d is the space private key, AES is the first encryption key, EX is the exchange key, c ₂ is the second passphrase, c ₃ is the third passphrase, ekey ₂ is the second emergency key, user _k _ekey ₂ is user k's user public key

A second emergency key corresponding to user k generated by encrypting the first encryption key AES with , _key E may mean an encryption function using the key key, and _key D may mean a decryption function using the key key.

에 해당할 수 있다.According to an embodiment, when the manager's device loses the space private key, it may request 710 recovery of the space private key to the server. In response to the request for recovery of the space private key, the server responds to information about at least one user's account corresponding to the second emergency key {user ₁ , user ₂ , . . . , user _n } and the second passphrase may be provided to the manager's device (720). The information about the user's account corresponding to the second emergency key may include a list of user accounts corresponding to the user's public key used to generate the second emergency key. The second passphrase is the passphrase stored in the server by encrypting the space private key with the first encryption key.

may correspond to

According to an embodiment, the administrator's device selects one of the provided user accounts (eg, user ₂ ) and requests the server for a second emergency key corresponding to the selected user's account (730) can do. Hereinafter, an example will be described in which the administrator's device selects the second user's account user ₂ and requests the second emergency key corresponding to the second user's account.

Upon receiving the request for the second emergency key corresponding to the second user's account from the manager's device, the server may provide the second emergency key user _{2_ekey 2} corresponding to the second user's account to the manager's device (740) there is.

The manager's device may transmit the exchange key to the second user's device through the server (750). The second user's device may refer to a device logged into the second user's account. For example, the administrator's device may request the server to transmit an exchange key to the user's account corresponding to the second emergency key, and the server may transmit the exchange key to the second user's device.

According to an embodiment, the exchange key is a key for encrypting a user private key, and the exchange key may correspond to a symmetric key or an asymmetric key. If the exchange key is an asymmetric key, the exchange key transmitted to the device of the second user may correspond to an encryption key of the exchange key. Transmitting the exchange key (750) may include requesting the second user's user private key from the second user's device. In other words, sending the exchange key may include requesting the user's private key.

According to one embodiment, when the manager's device requests the server for the second emergency key corresponding to the account of the second user, the exchange key may be transmitted to the server along with the request. In other words, operation 730 of requesting the second emergency key corresponding to the account of the second user of the manager's device may include operation 750 of transmitting the exchange key to the device of the second user through the server. .

을 생성(760)할 수 있으며, 제3 암호문은 서버를 통해 관리자의 디바이스로 전달(770)될 수 있다.According to an embodiment, the second user's device uses the received exchange key to encrypt the second user's user private key and third ciphertext

It can generate (760), and the third cipher text can be delivered to the manager's device through the server (770).

According to an embodiment, the device of the second user may perform an operation of authenticating the device of the administrator before transmitting the third password text. For example, the second user's device can check whether the manager's device that sent the exchange key is an account designated as the manager of the space that includes the second user's account. 3 ciphertext can be transmitted.

According to an embodiment, the manager's device receiving the third encrypted text from the second user's device may decrypt the third encrypted text with an exchange key to obtain the user private key of the second user (780). If the exchange key is an asymmetric key, the administrator's device can decrypt the ciphertext using the decryption key of the exchange key.

The manager's device may obtain the first encryption key by decrypting the second emergency key using the obtained user private key of the second user (790). The device of the administrator who has obtained the first encryption key may obtain the space private key by decrypting the second ciphertext with the first encryption key (791). In other words, the space private key lost in the manager's device can be restored based on the second emergency key, and the restored space private key can be stored in the manager's device.

8 is an operation flowchart of a secure instant messaging method performed in a manager's device according to an embodiment.

Referring to FIG. 8 , the secure instant messaging method performed on the administrator's device according to an embodiment includes generating a second ciphertext obtained by encrypting a space private key with a first encryption key and storing the second ciphertext in a server (810), the space private key Receiving a second emergency key and a second passphrase from the server for recovery (820), transmitting an exchange key to a device of a second user logged in with an account of the second user corresponding to the second emergency key. (830), based on the exchange key, obtaining (840) the user private key of the second user, and based on the first encryption key and the second ciphertext, recovering (850) the space private key. can do.

The secure instant messaging method performed in the manager's device shown in FIG. 8 may correspond to the operations of the manager's device described above with reference to FIGS. 6 and 7 . For example, step 810 may correspond to the operation of the manager's device described above with reference to FIG. 6 , and steps 820 to 850 may correspond to the operation of the manager's device described above with reference to FIG. 7 . At least one user and administrator may be included in a space provided by the secure instant messaging service. The at least one user may include a second user.

Step 810 according to an embodiment may include storing the second ciphertext in a server corresponding to the space. As described above, the first encryption key for encrypting the space private key may be generated in the administrator's device. The manager's device may store a key for decrypting the first encryption key. For example, the manager's device may store the first encryption key when the first encryption key is a symmetric key, and may store a decryption key generated as a pair with the first encryption key when the first encryption key is an asymmetric key.

Step 820 according to an embodiment includes obtaining a second emergency key including at least one cipher text obtained by encrypting the first encryption key with the user public key of at least one user, and the second cipher text stored in step 810. It may include the step of obtaining. The second emergency key may be performed when the space private key is lost in the manager's device. The first emergency key may include at least one ciphertext obtained by encrypting the first encryption key with the user public key of at least one user, and the ciphertext obtained by encrypting the first encryption key with the user public key of the second user is the second user's ciphertext. A second emergency key corresponding to the account may be included. The manager's device may request a second emergency key corresponding to the second user's account stored in the server, and may obtain the second emergency key corresponding to the second user's account from the server. For example, the manager's device may obtain a location where the second emergency key is stored and may request the second emergency key from the server.

Step 830 according to an embodiment may include transmitting an exchange key for encrypting a user private key of the second user to a device of the second user logged in with an account of the second user. As described above, transmitting 830 the exchange key may include requesting a user private key.

Obtaining the user private key of the second user according to an embodiment (840) includes receiving a third ciphertext obtained by encrypting the user private key of the second user with an exchange key from the second user's device, and using the exchange key as the third cipher text. Decrypting the ciphertext may include obtaining a user private key of the second user. The device of the second user may generate third cipher text obtained by encrypting the user private key of the second user based on the received exchange key, and transmit the third cipher text to the device of the manager, and the device of the manager may obtain the third cipher text. In the administrator's device, the third ciphertext may be decrypted with the exchange key, and as a result of decryption of the third ciphertext, the user private key of the second user may be obtained.

Obtaining the user private key of the second user according to an embodiment (840) includes requesting administrator authentication from the device of the second user and obtaining the user private key of the second user based on the administrator's authentication. steps may be included. As described above, the device of the second user may check whether the sender of the request for the user private key is the manager of the space to which the account of the second user belongs, and if the manager is identified, the user private key may be encrypted and transmitted. there is.

If the administrator's authentication fails in step 840 according to an embodiment, the administrator's device may not be able to obtain the third password text.

Step 850 according to an embodiment may further include obtaining a first encryption key by decrypting the second emergency key with the user private key of the second user. In other words, the first encryption key may be obtained by decrypting the second emergency key corresponding to the second user's account obtained in step 820 with the user private key of the second user obtained in step 840 .

Step 850 of recovering the space private key according to an embodiment may include recovering the space private key by decrypting the second ciphertext using the first encryption key. The manager's device may acquire access rights to the space private key by storing the obtained space private key or storing it in a secure medium accessible from the manager's device.

9 is an operation flowchart of a secure instant messaging method performed in a server according to an embodiment.

Referring to FIG. 9 , a secure instant messaging method performed in a server according to an embodiment includes storing a second cipher text obtained by encrypting a space private key received from a manager's device with a first encryption key (910), and at least one Storing a second emergency key corresponding to each of the at least one user's account (920), transmitting second password text and information about the user's account corresponding to the second emergency key to an administrator's device (930) ), and transmitting the second emergency key stored in correspondence to the account of the second user to the manager's device (940).

The secure instant messaging method performed by the server shown in FIG. 9 may correspond to the operation of the server described above with reference to FIGS. 6 and 7 . For example, steps 910 and 920 may correspond to the operation of the server described above in FIG. 6, and steps 930 and 940 may correspond to the operation of the server described above in FIG. 7 .

Step 910 according to an embodiment may include storing the second passphrase generated by the manager's device in correspondence with the space to which the manager belongs.

Step 920 according to an embodiment may include storing at least one second emergency key obtained by encrypting the first encryption key with the user public key of the at least one user in correspondence with each account of the at least one user. there is. At least one user and administrator may be included in a space provided by the secure instant messaging service.

According to one embodiment, the at least one second emergency key may be received from a manager's device or may be received from a device of a user other than the manager included in the space (eg, a third user). For example, a device of a user other than the manager (eg, a third user) included in the space may correspond to a device of a user who has received the first encryption key from the manager's device. In other words, storing at least one second emergency key corresponding to each account of at least one user (920) includes at least one encryption key obtained by encrypting the first encryption key with the user public key of at least one user from the manager's device. Receiving a second emergency key of and receiving at least one second emergency key obtained by encrypting the first encryption key with the user public key of at least one user from the user's device that has received the first encryption key from the manager's device It may include at least one of the steps of Hereinafter, a case where a device of a user other than the manager receiving the second emergency key is a device of the second user will be described as an example.

As described above, the device of the third user may receive the second emergency key corresponding to the account of the third user in which the first encryption key is encrypted with the user public key of the third user from the device of the manager, and the received 2 The first encryption key may be obtained by decrypting the emergency key with the user private key of the third user.

Step 920 according to an embodiment stores at least one second emergency key corresponding to each of the at least one user account in order to identify a user account corresponding to the user public key that encrypts the second emergency key. It may correspond to the step of

For example, the step 910 of storing at least one second emergency key corresponding to each account of at least one user may be performed at regular intervals, and the number of received second emergency keys may correspond to a predetermined number. can As another example, the step 910 of storing at least one second emergency key corresponding to each of the at least one user's account may be performed as the new user's account is included in the space.

Step 930 according to an embodiment includes providing information about the user's account corresponding to the second passphrase and the second emergency key to the manager's device in response to the request for recovery of the space private key received from the manager's device. steps may be included. Information about at least one user account corresponding to the second emergency key may include a list of user accounts corresponding to the user public key used to generate the second emergency key stored in the server in correspondence with the space.

As described above, the administrator's device can obtain the location where the second cipher text is stored, and can request the second cipher text from the server. For example, another user's device may not be able to obtain a location where the second cipher text is stored, and thus may not be able to request the second cipher text from the server. As another example, when the second cipher text can be requested without based on the location where the second cipher text is stored in the server, the server may not transmit the second cipher text when a request for the second cipher text is received from a user other than the administrator. can In other words, the server may operate to transmit the second encrypted text in response to a request for the second encrypted text received from the device identified as the manager's device.

Step 940 according to an embodiment, in response to an administrator's input for selecting a second user's account from among at least one user's account based on information about the user's account, stored in correspondence with the second user's account and transmitting the second emergency key to the manager's device. The input for selecting the account of the second user may correspond to an input received from the manager's device. The administrator's device may select any one of the user accounts corresponding to the user key used to generate the second emergency key based on the user account information provided from the server, and correspond to the user account selected by the server. may request a second emergency key. The second emergency key corresponding to the account of the selected user may correspond to the first encryption key encrypted with the user public key of the selected user.

10 is an operation flowchart of a secure instant messaging method performed in a device of a third user according to an embodiment.

Referring to FIG. 10 , a secure instant messaging method performed on a third user's device according to an embodiment includes acquiring a second emergency key corresponding to the third user's account from a manager's device (1010). It may include obtaining a first encryption key by decrypting the second emergency key with a user private key of a third user (1020), and generating and storing at least one second emergency key in a server (1030). .

The secure instant messaging method performed by the third user's device shown in FIG. 10 may correspond to the operation of the third user's device described above with reference to FIG. 6 .

Step 1010 according to an embodiment may include acquiring a second emergency key corresponding to an account of a third user in which the first encryption key is encrypted with the user public key of the third user, from the manager's device. . In other words, the second emergency key corresponding to the account of the third user may correspond to cipher text obtained by encrypting the first encryption key with the user public key of the third user.

The device of the third user may obtain a first encryption key through step 1020 according to an embodiment, and the obtained first encryption key is encrypted with the user public key of another user through step 1030 to obtain a second encryption key. It can be stored on the server as an emergency key. The second emergency key may include at least one ciphertext obtained by encrypting the first encryption key with at least one user public key of another user. In other words, step 1030 according to an embodiment may include generating at least one second emergency key obtained by encrypting the first encryption key with the user public key of at least one other user and storing the second emergency key in a server. The other user may correspond to a user included in a space including an administrator and a third user. The user public key of another user may be obtained from the server. As described above, the second emergency key can be generated not only in the manager's device, but also in the device of a third user who is a user other than the manager included in the space.

11 is an exemplary view of a configuration of a device according to an embodiment.

Referring to FIG. 11 , an apparatus 1100 includes a processor 1101 , a memory 1103 and an input/output device 1105 . The apparatus 1100 may include, for example, a user's device (eg, a smart phone, a personal computer, a tablet PC, etc.) and a server.

Device 1100 according to an embodiment may include a device that performs the secure instant messaging method described above. For example, the device 1100 may include a server that performs the secure instant messaging method described above with reference to FIGS. 1 to 10 , an administrator's device, and/or a third user's device.

The processor 1101 according to an embodiment may perform at least one method described above through FIGS. 1 to 10 . For example, the processor 1101 of the server may perform the secure instant messaging method performed in the server described above with reference to FIGS. 5 and/or 9, and the processor 1101 of the administrator's device may The secure instant messaging method performed on the manager's device described above with reference to FIG. 8 can be performed, and the processor 1101 of the third user's device can perform the secure instant messaging performed with the device of the third user described above with reference to FIG. 10 . way can be done.

The memory 1103 according to an embodiment may store information related to the above-described secure instant messaging method and may store data for performing the above-described secure instant messaging method. Memory 1103 may be volatile memory or non-volatile memory.

The device 1100 according to one side may be connected to an external device (eg, a personal computer or network) through the input/output device 1105 and exchange data. For example, the device 1100 may receive a request transmitted from another device through the input/output device 1105 and output data or a signal corresponding to the request.

According to an embodiment, the memory 1103 may store a program in which the above-described secure instant messaging method is implemented. The processor 1101 may execute a program stored in the memory 1103 and control the device 1100 . Program codes executed by the processor 1101 may be stored in the memory 1103 .

The embodiments described above may be implemented as hardware components, software components, and/or a combination of hardware components and software components. For example, the devices, methods and components described in the embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate (FPGA). array), programmable logic units (PLUs), microprocessors, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and software applications running on the operating system. A processing device may also access, store, manipulate, process, and generate data in response to execution of software. For convenience of understanding, there are cases in which one processing device is used, but those skilled in the art will understand that the processing device includes a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that it can include. For example, a processing device may include a plurality of processors or a processor and a controller. Other processing configurations are also possible, such as parallel processors.

Software may include a computer program, code, instructions, or a combination of one or more of the foregoing, which configures a processing device to operate as desired or processes independently or collectively. The device can be commanded. Software and/or data may be any tangible machine, component, physical device, virtual equipment, computer storage medium or device, intended to be interpreted by or provide instructions or data to a processing device. , or may be permanently or temporarily embodied in a transmitted signal wave. Software may be distributed on networked computer systems and stored or executed in a distributed manner. Software and data may be stored on computer readable media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. A computer readable medium may store program instructions, data files, data structures, etc. alone or in combination, and program instructions recorded on the medium may be specially designed and configured for the embodiment or may be known and usable to those skilled in the art of computer software. there is. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. - includes hardware devices specially configured to store and execute program instructions, such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter, as well as machine language codes such as those produced by a compiler.

The hardware device described above may be configured to operate as one or a plurality of software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on this. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims (21)

In the secure instant messaging method performed on the manager's device,
Generating and storing a first emergency key corresponding to the space private key, wherein the first emergency key includes at least one ciphertext obtained by encrypting the space private key with the user public key of at least one user, and storing the first emergency key in a server;
obtaining a first emergency key corresponding to an account of a first user from the server in order to recover the space private key;
transmitting an exchange key to a device of the first user logged in with an account of the first user;
obtaining a user private key of the first user based on the exchange key; and
recovering the space private key by decrypting the obtained first emergency key with a user private key of the first user;
including,
A secure instant messaging method.
According to claim 1,
The administrator and the at least one user are included in a space provided by a secure instant messaging service, wherein the space is a unit including at least one chat room and at least one user.
A secure instant messaging method.
According to claim 2,
The space private key is
In the device of the administrator who manages the space, generated with an asymmetric key corresponding to the space,
A secure instant messaging method.
According to claim 1,
Obtaining the user private key of the first user
receiving a first cipher text obtained by encrypting the user private key of the first user with the exchange key from a device of the first user; and
obtaining a user private key of the first user by decrypting the first cipher text with the exchange key;
including,
A secure instant messaging method.
According to claim 1,
Obtaining the user private key of the first user
requesting authentication of the administrator to the device of the first user; and
Obtaining a user private key of the first user based on the administrator's authentication.
containing
A secure instant messaging method.
In the secure instant messaging method performed in the server,
receiving at least one first emergency key obtained by encrypting a space private key with a user public key of at least one user, from a manager's device;
storing the received at least one first emergency key corresponding to each account of the at least one user;
providing information about the account of the at least one user corresponding to the at least one first emergency key to the manager's device in response to a request for recovery of the space private key received from the manager's device; and
Transmitting a first emergency key stored in correspondence with the account of the first user to the device of the manager in response to an input for selecting an account of the first user from among the accounts of the at least one user based on the information.
including,
A secure instant messaging method.
In the secure instant messaging method performed on the manager's device,
generating a second ciphertext obtained by encrypting the space private key with the first encryption key and storing the second ciphertext in a server;
In order to recover the space private key, a second emergency key from the server—the second emergency key includes at least one cipher text obtained by encrypting the first encryption key with a user public key of at least one user—and the first 2 obtaining ciphertext;
transmitting an exchange key to a device of a second user logged in with an account of the second user corresponding to the second emergency key;
obtaining a user private key of the second user based on the exchange key; and
recovering the space private key based on the first encryption key and the second ciphertext obtained by decrypting the second emergency key with a user private key of the second user;
including,
A secure instant messaging method.
According to claim 7,
The administrator and the at least one user are included in a space provided by a secure instant messaging service, wherein the space is a unit including at least one chat room and at least one user.
A secure instant messaging method.
According to claim 8,
The space private key is
In the device of the administrator who manages the space, generated with an asymmetric key corresponding to the space,
A secure instant messaging method.
According to claim 7,
Obtaining the user private key of the second user
receiving third ciphertext obtained by encrypting the user private key of the second user with the exchange key from the device of the second user; and
obtaining a user private key of the second user by decrypting the third cipher text with the exchange key;
including,
A secure instant messaging method.
According to claim 7,
Obtaining the user private key of the second user
requesting authentication of the manager to the device of the second user; and
Obtaining a user private key of the second user based on the administrator's authentication.
containing
A secure instant messaging method.
According to claim 7,
Recovering the space private key
recovering the space private key by decrypting the second ciphertext with the first encryption key;
including,
A secure instant messaging method.
In the secure instant messaging method performed in the server,
storing second cipher text obtained by encrypting the space private key received from the manager's device with the first encryption key;
storing at least one second emergency key obtained by encrypting the first encryption key with the user public key of at least one user in correspondence with each account of the at least one user;
providing information about the account of the user corresponding to the second passphrase and the second emergency key to the device of the administrator in response to a request for recovery of the space private key received from the device of the administrator; and
In response to the manager's input for selecting the second user's account from among the at least one user's account based on the information, the second emergency key stored in correspondence to the second user's account is stored in the manager's device. steps to transmit
including,
A secure instant messaging method.
According to claim 13,
The step of storing the at least one second emergency key corresponding to each of the at least one user account
receiving, from the manager's device, at least one second emergency key obtained by encrypting the first encryption key with the user public key of the at least one user; and
Receiving at least one second emergency key obtained by encrypting the first encryption key with the user public key of the at least one user from a device of a third user who has obtained the first encryption key from the device of the manager.
including at least one of
A secure instant messaging method.
A secure instant messaging method performed on a device of a third user, comprising:
obtaining, from an administrator's device, a second emergency key corresponding to an account of the third user in which the first encryption key is encrypted with the user public key of the third user;
obtaining the first encryption key by decrypting the obtained second emergency key with a user private key of the third user; and
Generating at least one second emergency key obtained by encrypting the first encryption key with at least one user public key of another user and storing the second emergency key in a server.
including,
A secure instant messaging method.
A computer program stored in a medium to be combined with hardware to execute the method of any one of claims 1 to 15.
A first emergency key corresponding to the space private key, wherein the first emergency key includes at least one ciphertext obtained by encrypting the space private key with the user public key of at least one user, is generated and stored in a server;
To recover the space private key, obtain a first emergency key corresponding to an account of a first user from the server;
Transmitting an exchange key to the device of the first user logged in with the account of the first user;
Obtaining a user private key of the first user based on the exchange key;
Decrypting the obtained first emergency key with a user private key of the first user to recover the space private key;
at least one processor
including,
The manager's device.
Receiving at least one first emergency key obtained by encrypting the space private key with the user public key of at least one user from the manager's device;
storing the received at least one first emergency key in correspondence with each account of the at least one user;
In response to a request for recovery of the space private key received from the manager's device, information about the account of the at least one user corresponding to the at least one first emergency key is provided to the manager's device,
In response to an input for selecting an account of a first user from among the accounts of the at least one user based on the information, transmitting a first emergency key stored in correspondence to the account of the first user to the device of the manager,
at least one processor
including,
server.
Generating and storing a second passphrase obtained by encrypting the space private key with the first encryption key in a server;
In order to recover the space private key, a second emergency key from the server—the second emergency key includes at least one cipher text obtained by encrypting the first encryption key with a user public key of at least one user—and the first 2 obtain the ciphertext;
Transmitting an exchange key to the second user's device logged in with the second user's account corresponding to the second emergency key;
Obtaining a user private key of the second user based on the exchange key;
Recovering the space private key based on the first encryption key and the second ciphertext obtained by decrypting the second emergency key with the user private key of the second user,
at least one processor
including,
The manager's device.
Stores a second ciphertext obtained by encrypting the space private key received from the administrator's device with the first encryption key;
storing at least one second emergency key obtained by encrypting the first encryption key with a user public key of at least one user corresponding to each account of the at least one user;
Responding to a request for recovery of the space private key received from the manager's device, providing information about the user's account corresponding to the second passphrase and the second emergency key to the manager's device;
In response to the manager's input for selecting the second user's account from among the at least one user's account based on the information, the second emergency key stored in correspondence to the second user's account is stored in the manager's device. transmitting,
at least one processor
including,
server.
obtaining, from an administrator's device, a second emergency key corresponding to an account of a third user in which a first encryption key is encrypted with a user public key of the third user;
Obtaining the first encryption key by decrypting the obtained second emergency key with a user private key of the third user;
Generating at least one second emergency key obtained by encrypting the first encryption key with a user public key of at least one other user and storing the second emergency key in a server,
at least one processor
including,
Third-Party User's Device.

Images