WO2019215493A1 - Secure method and system for the delayed sharing of data between a plurality of sender users and a recipient user - Google Patents

Abstract

Disclosed is a method for sharing files (2) between N users (Ai) and a recipient user (B), said method involving three phases: - writing: ◦ in a file server (5), creating, on the initiative of a master sender user (A1), a data container (6) assigned to user B; ◦ during a writing time (T1), giving each sender user (Ai) writing access to the container (6); - archiving: ◦ upon expiration of the writing time (T1), blocking access to the container (6) for each sender user (Ai); ◦ encrypting the data in the container (6) using the recipient user's (B) public key (ZB); ◦ during an archiving time (T2), storing the encrypted container (6B) in a file server (5); - sharing: allowing the recipient user (B) to download the encrypted container (6B) for decryption thereof using his or her private key (BZ).

Description

 Secure method and system for delayed data sharing between multiple sending and receiving users

The invention relates to the field of computing, and more specifically the sharing of computer data files between several sending users and a recipient user.

 The term "user" is used here to designate a device communicating (in English "user device"), typically a smartphone, a tablet, or more generally a computer, e.g. a laptop or stationary or a workstation, able to connect, via a local computer network (LAN), metropolitan (MAN) or extended (WAN, typically the Internet), to a remote server, the term "server Designating here a physical unit or, in a virtualization frame, a computing space and / or memory allocated within a physical unit and on which runs an operating system or operating system emulation.

 Nevertheless it is understood that associated with such a customer electronic device a real user (that is to say a natural or legal person) who performs operations from this device.

 The use of computer networks is now quite widespread, especially for data sharing.

 There are various types of systems for sharing data.

 Mailbox e-mail, which operates asynchronously, allows a user A (sender) to send a user B (recipient) a message containing information that can be included in the body of the message itself. , or as attached files.

 In an e-mail, the delay in routing the message depends essentially on the bandwidth (availability) of the network connecting the sender user and the recipient user, and the memory size of the message, including its contents. possible attachments.

Often, the routing takes a few seconds. The recipient can then open and read the message from the sender whenever he wants. At the time when these lines are written, e-mail is limited in terms of the size of the messages transmitted, most often about ten megabytes (MB).

 In addition, e-mail does not allow multiple users to group together to address a message to a recipient.

 To exchange large volume data (that is, larger than 10 MB), or to allow multiple sending users to share data with a recipient user, it has become common practice to use specialized platforms. , eg. Dropbox (registered trademark).

 In principle, these platforms are intended to allow permanent access to a private memory space on which files are stored, for any user identified as entitled.

 File piracy involves either unauthorized access to this memory space or the spoofing of an access user's identity.

 These platforms are easy to use but have limitations in securing data. In particular, identity theft is very effective for accessing data immediately, and - in general - both in reading and writing.

 It therefore remains a need to share computer data files between users, with a higher degree of security, while maintaining a certain simplicity of use.

 For this purpose, it is proposed, in the first place, a method of sharing computer data files between N (N an integer, N> 2), sending users and a recipient user, via a computer system equipped with:

 From a communication server,

 At least one file server, and

A database of profiles containing in memory profiles associated respectively with the users, each profile comprising at least one identifier and at least one public cryptographic key to which a private key corresponds; A control unit, connected to the communication server, the file server and the database;

 This method comprises, at the system level, three successive phases:

 A write phase, which includes the operations of:

 o Receiving from a master sender user a request containing an instruction for creating a data container to be shared, an identifier of each sender user (other than the master sender user) and an identifier of the recipient user;

 o Create the container in a file server;

 o Associate the container with the corresponding profile, in the database, with the recipient user;

 o Associate with the container a predetermined delay of writing;

 o As long as the write delay has not expired, allow each sending user write access to the container;

An archiving phase, which includes the following operations: o At the expiration of the write delay, prohibit sending users access, at least in writing, to the container;

 o Encrypt the container using the recipient's public key to form an encrypted container;

 o Associate with the encrypted container a predetermined archiving delay;

 o As long as the archiving time has not expired, store the encrypted container in a file server and deny access to at least the recipient user;

 A sharing phase, which includes the operation of, upon expiration of the archiving period, allowing the recipient user to download the encrypted container for decryption with his private key.

 Various additional features may be provided, alone or in combination. For example:

 The write delay can be set by the master sender user or automatically.

Similarly, the archiving time can be set by the master sender user or automatically. It is advantageously provided for the reception by the communication server of a notification of decryption of the container by the recipient user. In this case, it is also preferably provided for the destruction of the encrypted container on the file server after receiving the decryption notification by the recipient user.

 The container is advantageously subdivided into several own memory spaces, each allocated to a respective sender user. In this case, access by a sender user to a memory space of another sender user is preferably prohibited.

Secondly, it proposes a computer system which, for the implementation of the method as presented above, comprises:

 A communication server,

 At least one file server, and

 A database of profiles containing in memory profiles associated respectively with the users, each profile comprising at least one identifier and at least one public cryptographic key to which a private key corresponds,

 This system further comprising a control unit comprising a programmable memory containing instructions for operating:

 A write phase, which includes the operations of:

 o Receiving from a master sender user a request containing an instruction for creating a data container to be shared, an identifier of each sender user (other than the master sender user) and an identifier of the recipient user;

 o Create the container in a file server;

 o Associate the container with the corresponding profile, in the database, with the recipient user;

 o Associate with the container a predetermined delay of writing;

 o As long as the write delay has not expired, allow each sending user write access to the container;

An archiving phase, which includes the following operations: o At the expiration of the write delay, prohibit sending users access, at least in writing, to the container; o Encrypt the container using the recipient's public key to form an encrypted container;

 o Associate with the encrypted container a predetermined archiving delay;

 o As long as the archiving time has not expired, store the encrypted container in a file server and deny access to at least the recipient user;

 A sharing phase, which includes the operation of, upon expiration of the archiving period, allowing the recipient user to download the encrypted container for decryption with his private key.

 Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given hereinafter with reference to the accompanying drawings, in which:

 FIG. 1 is a synthetic diagram of a computer system illustrating the writing phase of a method according to the invention;

 FIG. 2 is a diagram similar to FIG. 1, illustrating the archiving phase;

 FIG. 3 is a diagram similar to FIG. 1, illustrating the sharing phase;

 FIG.4 is a diagram illustrating various steps of the method of the invention.

 FIG. 1 to FIG. 3 shows a computer system 1 intended to allow the sharing of computer data files 2 between N users Ai transmitters (where N is an integer such that N> 2 and i an integer such as 1 <i <N) and a recipient user B. The term "user" here refers, concretely, to an electronic device, such as a smartphone, a computer, a tablet, and provided with a communication interface (wired or wireless) through which this device is capable to connect to a remote server, via a local 3 (LAN), metropolitan (MAN) or extended (WIDE, such as the Internet). However, it is understood that, by extension, the term "user" indirectly refers to one or more real users (eg a natural or legal person) associated with this device.

The computer system 1 comprises, in the first place, a communication server 4, programmed to be able to establish training sessions. communication (preferably secure) with users (including users Ai and B).

 The computer system 1 comprises, secondly, a file server, on which directories or "containers" 6 of data files to be shared can be created. In these containers can be created, deposited, copied, pasted, deleted, modified, data files 2 of any type, e.g. files from office applications (eg word processing, spreadsheets), sound files, image files, or video files.

 The computer system 1 comprises, thirdly, a database 7 of profiles that contains in memory profiles PAi, PB users. In this case, the database contains at least one PAi profile associated with each user Ai issuer, and a profile PB associated with the user B recipient.

 Each PAi, PB user profile comprises at least one IDAi IDB, IDB linked to the corresponding user (eg a name, an email address, a phone number) and at least one public cryptographic key ZAi, ZB.

 To this key ZAi, public cryptographic ZB corresponds to a cryptographic key AiZ, private BZ.

 The private cryptographic key AiZ, BZ associated with each user Ai issuer or, respectively, the user B recipient, is stored locally in a respective memory space thereof.

 The computer system 1 comprises, fourthly, a control unit 8, connected to the communication server 4, to the file server 5 and to the data base 7. The control unit 8 comprises at least one processor and a programmable memory. The control unit 8 is programmed to control the communication server 4, the file server 5 and to administer the database 7.

 The control unit 8 (and more precisely its memory) comprises instructions for performing operations grouped into several successive phases.

 A first phase, called writing, includes the operations of:

o Receiving from a user A1 transmitter master a request containing an instruction to create a container 6, a identifier IDAi (i> 2) of each other user Ai (i> 2) issuer, and an identifier IDB of the user B recipient; o Create the container 6 in a file server 5;

 o Associate the container 6 with the profile associated with the user B in the database 7;

 o Associate with the container 6 a predetermined delay T1 write; o As long as the write T1 delay has not expired, allow each sending user Ai write access to the container 6

 In practice, the user A1 transmitter master addresses the computer system 1, via the network 3, the creation request of the container 6. This request transits through the communication server 4, which performs the user identity checks A1 master transmitter, typically by comparison of information communicated by it (eg a password) with information associated with its IDA1 profile as stored in the database 7. As soon as the user A1 master transmitter is identified, access is given to it (possibly by another communication channel, as shown in FIG. 1) to the file server 5.

 The system 1 verifies that the identifiers IDAi (i> 2) communicated by the user A1 emitter master actually correspond to user profiles PAi stored.

 Therefore, during the write phase, each user Ai issuer is allowed to modify the container 6 by adding or subtracting 2 files of data. These data files 2 can come from each terminal Ai itself, or be downloaded from remote servers via the network 3.

 The writing delay T1 (schematized on the drawings by a first countdown) can be defined by the user A1 master, or automatically by the control unit 8. The write delay T1 is advantageously implemented within the computer system 1, e.g. by means of an internal clock controlled by (or integrated with) the control unit 8.

According to a preferred embodiment illustrated in FIG. 4, the container 6 is subdivided into a plurality of self-memory spaces 6, each allocated to a respective user Ai issuer - that is, the data files 2 deposited by each user Ai transmitter in its space 6.i own memory do not affect the data files 2 deposited by another user Aj sender (j an integer such that j ¹ i) in its own memory space 6.j.

 It is even preferable that access (read and / or write) by a user Ai issuer be denied to a space 6.j own memory allocated to another user Aj issuer.

 A second phase, called archiving, includes the operations of:

 o At the expiration of the writing delay T1, prohibit each user Ai issuer access, at least in writing, to the container 6;

 o Encrypting the container 6 using the public ZB key of the user B recipient to form an encrypted container 6B; o Associate with the encrypted container 6B a predetermined T2 storage delay;

 o As long as the archiving time T2 has not expired, store the encrypted container 6B in a file server 5 by prohibiting access at least to the user B recipient.

 The archiving time T2 (schematized on the drawings by a second countdown) can be defined by the user A1 master, or automatically. The archiving delay T2 is advantageously implemented within the computer system 1, e.g. by means of an internal clock controlled by (or integrated with) the control unit 8.

 The archiving time T2 is advantageously greater than one hour. It is preferably greater than one day. It can reach a month, or even one or more years.

 According to a preferred embodiment, the control unit 8 has no instructions for communicating to the recipient user B during the archiving phase the very existence of a container 6 or an encrypted container 6B. to his attention, so that the actual user (or actual users) associated with the recipient user B is (are) kept in ignorance of this existence.

A third phase, called the sharing phase, includes the operation consisting, at the expiration of the archiving delay T2, in enabling the recipient user B to download the encrypted container 6B in order to decrypt it with the aid of its private BZ key. In practice, the control unit 8 is e.g. programmed to address to the user B recipient (including via the communication server 4) a notification of provision of the container 6B encrypted. This notification advantageously contains the identifiers IDAi associated with the users Ai transmitters. The download is then preferably controlled by the user B recipient, rather than done automatically on command of the control unit 8. The knowledge of the IDAi profile of the user Ai issuers by the user B recipient may constitute for it a confidence index of the origin and / or the safety of the data shared by the users Ai issuers.

 Specifically, the encrypted container 6B is sent, on command of the control unit 8, to the user B recipient via the network 3. The decryption is performed locally by the user B recipient, through its key BZ privately stored locally. The recipient user B can then read (and if necessary write) the container 6, that is to say the data files 2 that it contains, as deposited at the initiative of the users Ai issuers .

 At the end of the decryption, the data files 2 can be stored locally by the user B recipient.

 At the end of the decryption, the user B recipient can address (automatically or on an external command) to the system 1 a decryption notification. This notification is received by the communication server 4.

 In this case, the destruction of the encrypted container 6B on the file server 5 is advantageously provided after the system 1 has received the decryption notification.

 In this way, memory space is released within the file server, which facilitates the subsequent creation of new containers 6.

The method (and the system) that has just been presented offers a certain security advantage compared with known methods (respectively systems). Indeed, during the archiving phase, the data of the files 2 can not be read - or even modified - by the users A transmitters or by the user B recipient. Any impersonation of any one of them is inoperative if it is necessary to have the private key of the user B to decrypt the container 6B. It can also be seen that the control exercised by the users A transmitters on the container 6 (that is to say on the data files 2 to share) ceases at the expiration of the write delay T 1, even though its content is not yet accessible for the user B recipient. The (predetermined) delay with which the recipient user B accesses the files 2 of data shared by the users Ai issuers makes it impossible any dialogue between them in real time, to the benefit of the parsimony with which the users exchange data between them. This results in particular an optimization of the bandwidth required, in networks, exchanges between users.

Claims

REVE N DICATIO NS 1. A method of sharing files (2) of computer data between N users (Ai) issuers (N an integer, N> 2; i an integer such as 1 <i <N), and a user (B) recipient, via a computer system (1) equipped:  A communication server (4),  At least one server (5) of files, and  A database (7) of profiles data containing in memory profiles (P Ai, PB) associated respectively with the users (Ai, B), each profile (PAi, PB) comprising at least one identifier (IDAi, IDB) and at least one public cryptographic key (ZAi, ZB) to which a private key (AiZ, BZ) corresponds;  A control unit (8), connected to the communication server (4), to the file server (5) and to the database (7) of data;  This method being characterized in that it comprises, at the level of the system (1), three successive phases:  A write phase, which includes the operations of:  o Receiving from a user (A1) master transmitter a request containing an instruction for creating a container (6) of data to be shared, an identifier (I DAi where i> 2) of each user (Ai where i> 2 ) issuer and an identifier (I DB) of the recipient user (B);  o Create the container (6) in a server (5) of files;  o Associate the container (6) with the corresponding profile (IDB) in the data base (7) to the recipient user (B); o Associating with the container (6) a predetermined delay (T1) of writing;  o As long as the write delay (T1) has not expired, allow each sending user (Ai) write access to the container (6); An archiving phase, which includes the following operations: o At the expiration of the write delay (T1), prohibit the users (Ai) issuers access, at least in writing, to the container (6); o Encrypting the container (6) using the recipient's public (B) public key (Z) to form an encrypted container (6B);  o Associating with the encrypted container (6B) a predetermined (T2) archiving delay;  o As long as the archiving delay (T2) has not expired, store the encrypted container (6B) in a server (5) of files by prohibiting access to at least the recipient user (B); A sharing phase, which includes the operation of allowing the recipient user B to download the encrypted container (6B) for decryption using the expiry of the archiving delay (T2). of his private key (BZ).  2. Method according to claim 1, wherein the write delay (T1) is defined by the user (A1) master transmitter.  The method of claim 1, wherein the writing delay (T1) is automatically set.  4. Method according to one of claims 1 to 3, wherein the delay (T2) archiving is defined by the user (A1) master transmitter.  5. Method according to one of claims 1 to 3, wherein the delay (T2) archiving is automatically defined.  6. Method according to one of the preceding claims, wherein the container (6) is subdivided into a plurality of spaces (6.i) own memories, each allocated to a respective user (Ai) issuer.  7. Method according to one of the preceding claims, which comprises the reception, by the server (4) communication, a decryption notification of the container (6) by the user (B) recipient.  The method of claim 7, which comprises destroying the encrypted container (6B) on the file server (5) after receiving the decryption notification from the recipient user (B).  9. System (1) which, for the implementation of the method according to one of the preceding claims, comprises:  A server (4) for communication,  At least one server (5) of files, and A database (7) of profiles data containing in memory profiles (PAi, PB) associated respectively with the users (Ai, B), each profile (PAi, PB) comprising at least one identifier (IDAi, IDB) and at least one public cryptographic key (ZAi, ZB) to which a private key (AiZ, BZ) corresponds,  The system (1) further comprising a control unit (8) comprising a programmable memory containing instructions for operating:  A write phase, which includes the operations of:  o Receiving from a user (A1) master transmitter a request containing an instruction for creating a container (6) of data to be shared, an identifier (IDAi where i ¹ 1) of each user (Ai where i ¹ 1) issuer and an identifier (IDB) of the recipient user (B);  o Create the container (6) in a server (5) of files;  o Associate the container (6) with the corresponding profile (IDB) in the data base (7) to the recipient user (B); o Associating with the container (6) a predetermined delay (T1) of writing;  o As long as the write delay (T1) has not expired, allow each sending user (Ai) write access to the container (6);  An archiving phase, which includes the following operations: o At the expiration of the write delay (T1), prohibit the users (Ai) issuers access, at least in writing, to the container (6); o Encrypting the data of the container (6) using the public key (ZB) of the user (B) recipient to form an encrypted container (6B);  o Associating the encrypted container file (6B) with a predetermined (T2) archiving delay;  o As long as the archiving delay (T2) has not expired, store the encrypted container (6B) in a server (5) of files by prohibiting access to at least the recipient user (B); A sharing phase, which includes the operation of allowing the recipient user (B) to download the encrypted container (6B) for decryption at the expiration of the archiving timeout (T2). using his private key (BZ).