FR3081064A1 - SECURE METHOD AND SYSTEM FOR DELAYED DATA SHARING BETWEEN SEVERAL TRANSMITTER USERS AND ANOTHER USER. - Google Patents

Abstract

A method of sharing files (2) between N users (Ai) and a user (B) recipient, which comprises three phases: - Writing: ○ Create, in a server (5) files, at the initiative of a user (A1) master transmitter, a container (6) of data, associated with the user B; ○ During a writing delay (T1), allow each sending user (Ai) write access to the container (6); - Archiving: ○ At the expiration of the writing delay (T1), prohibit each user (Ai) transmitter access to the container (6); ○ Encrypt the data of the container (6) using the public key (ZB) of the recipient user (B); ○ During an archiving delay (T2), storing the encrypted container (6B) in a file server (5); - Sharing: allow the recipient user (B) to download the encrypted container (6B) for decryption using his private key (BZ).

Description

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

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

The term “user” is used here to designate a communicating device (in English “user device”), typically a smartphone, a tablet, or more generally a computer, for example. a portable or fixed computer or a workstation capable of connecting, 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 framework, a computing and / or memory space allocated within a physical unit and on which an operating system or an operating system emulation is running.

However, we understand that a real user (that is to say a natural or legal person) who carries out operations using this device is associated with such an electronic client device.

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

There are various types of systems for sharing data.

Mailbox-type e-mails, which work asynchronously, allow user A (sender) to address user B (recipient) a message containing information that can be included in the body of the message itself , or as attached files.

In an electronic messaging system, the message delivery time depends essentially on the bandwidth (availability) of the network connecting the sending and receiving users, and on the memory size of the message, including its any attachments.

Quite often, routing takes a few seconds. The recipient can then open and read the message from the sender whenever they want.

At the time of writing, e-mail is limited in size to the messages sent, usually around ten megabytes (MB).

In addition, electronic messaging does not allow several users to group together to send a message to a recipient.

To exchange data of large volume (that is to say of size greater than 10 MB) approximately, or to allow several sending users to share data with a recipient user, it has become usual to use specialized platforms , eg. DropBox (registered trademark).

In principle, these platforms aim to allow permanent access to a private memory space on which files are stored, for any user identified as having the right to it.

Hacking files involves either unauthorized access to this memory space, or the theft of the identity of a user with access rights.

These platforms are easy to use but nevertheless meet limits with regard to data security. In particular, identity theft is very effective in accessing data immediately, and - in general - both read and write.

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

To this end, it is proposed, firstly, 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:

From a communication server,

At least one file server, and

A profile database containing profiles associated with users respectively, 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 process comprising, at the system level, three successive phases:

A writing phase, which includes the operations of:

o Receive a request from a master sending user containing an instruction to create a data container to share, an identifier for each sending user (other than the master sending user) and an identifier for the receiving 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 the container with a predetermined writing period;

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

An archiving phase, which includes the operations of:

o At the end of the writing period, prohibit sending users from accessing, at least in writing, the container;

o Encrypt the container using the public key of the recipient user to form an encrypted container;

o Associate the encrypted container with a predetermined archiving period;

o Until the archiving period has expired, store the encrypted container in a file server by prohibiting access to it at least to the recipient user;

A sharing phase, which includes the operation, at the end of the archiving period, of allowing the recipient user to download the encrypted container in order to decrypt it using his private key.

Various additional characteristics can be provided, alone or in combination. So, for example:

The writing delay can be defined by the master sending user or automatically.

Likewise, the archiving period can be defined by the master sending user or automatically.

Advantageously, provision is made for the reception, by the communication server, of a notification of decryption of the container by the recipient user. In this case, provision is also preferably made for the destruction of the encrypted container on the file server after receipt of the decryption notification by the recipient user.

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

Secondly, a computer system is proposed which, for implementing 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 writing phase, which includes the operations of:

o Receive a request from a master sending user containing an instruction to create a data container to share, an identifier for each sending user (other than the master sending user) and an identifier for the receiving 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 the container with a predetermined writing period;

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

An archiving phase, which includes the operations of:

o At the end of the writing period, prohibit sending users from accessing, at least in writing, the container;

o Encrypt the container using the public key of the recipient user to form an encrypted container;

o Associate the encrypted container with a predetermined archiving period;

o Until the archiving period has expired, store the encrypted container in a file server by prohibiting access to it at least to the recipient user;

A sharing phase, which includes the operation, at the end of the archiving period, of allowing the recipient user to download the encrypted container in order to decrypt it using his private key.

Other objects and advantages of the invention will emerge in the light of the description of an embodiment, given below with reference to the appended 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 different stages of the process of the invention.

In FIG. 1 to FIG. 3 is shown a computer system 1, intended to allow the sharing of files 2 of computer data between N sending users Ai (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 designates, in concrete terms, 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 (LAN), metropolitan (MAN) or wide area network (WIDE, such as the Internet). It is understood, however, that, by extension, the term “user” indirectly designates one (or more) real user (s) (for example a natural or legal person) associated with this device.

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

The computer system 1 comprises, secondly, a file server 5, 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, 2 data files of any type, eg. files from office applications (eg word processing, spreadsheet), sound, image, or video files.

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

Each PAi, PB user profile includes at least one IDAi, IDB identifier linked to the corresponding user (eg a name, an e-mail address, a telephone number) and at least one public cryptographic ZAi, ZB key.

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

The key AiZ, private cryptographic BZ associated with each sending user Ai or, respectively, with the receiving user B, 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 database 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) includes instructions for carrying out operations grouped in several successive phases.

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

o Receive from a user A1 master transmitter a request containing an instruction to create a container 6, an identifier IDAi (i> 2) of each other user Ai (i> 2) transmitter, and an identifier IDB of l user B recipient;

o Create container 6 in a file server 5;

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

o Associate with container 6 a predetermined writing delay T1;

o As long as the T1 writing delay has not expired, allow each sending user Ai write access to container 6.

In practice, the user A1 master transmitter sends to the computer system 1, via the network 3, the request to create the container 6. This request passes through the communication server 4, which performs the identity checks of the user A1 master transmitter, typically by comparing information communicated by the latter (for example a password) with information associated with its profile IDA1 as stored in the database 7. As soon as the user A1 master transmitter is identified, access is given to him (possibly by another communication channel, as illustrated in FIG. 1) to the file server 5.

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

Therefore, during the writing phase, each sending user Ai is authorized to modify the container 6 by adding or subtracting from it data files 2. 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 (shown diagrammatically in the drawings by a first countdown) can be defined by the master user A1, or automatically by the control unit 8. The T1 writing delay is advantageously implemented within the IT system 1, e.g. by means of an internal clock controlled by (or integrated into) the control unit 8.

According to an advantageous mode illustrated in FIG. 4, the container 6 is subdivided into several spaces 6.i own memories, each allocated to a respective user Ai transmitter - that is to say that the data files 2 deposited by each Sender user Ai in its own memory space 6.i do not affect the data files 2 deposited by another sending user Aj (j an integer such as j ψ i) in its own memory space 6.j

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

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

o At the end of the T1 writing period, prohibit each sending user Ai access, at least in writing, to container 6;

o Encrypt container 6 using the public ZB key of recipient user B to form an encrypted container 6B;

o Associate with the encrypted container 6B a predetermined T2 archiving period;

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

The T2 archiving period (shown schematically in the drawings by a second countdown) can be defined by the A1 master user, or automatically. The T2 archiving period is advantageously implemented within the IT system 1, e.g. by means of an internal clock controlled by (or integrated into) the control unit 8.

The T2 archiving period 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 is devoid of instructions for communicating to the recipient user B, during the archiving phase, the very existence of a container 6 or of an encrypted container 6B to its attention, so that the real user (or real users) associated with user B recipient is (are) kept (s) in ignorance of this existence.

A third phase, called sharing, includes the operation consisting, at the end of the T2 archiving period, in allowing the recipient user B to download the encrypted container 6B with a view to decrypting it using his private BZ key.

In practice, the control unit 8 is, for example. programmed to send the recipient user B (in particular via the communication server 4) a notification of availability of the encrypted container 6B. This notification advantageously contains the IDAi identifiers associated with the sending Ai users. The download is then preferably ordered by the recipient user B, rather than carried out automatically on command from the control unit 8. Knowledge of the IDAi profile of the sending Ai users by the receiving user B can constitute for the latter an index of confidence in the source and / or the safety of the data shared by the sending Ai users.

Concretely, the encrypted container 6B is sent, on command of the control unit 8, to the recipient user B via the network 3. The decryption is carried out locally by the recipient user B, by means of his key BZ private locally stored. The recipient user B can then read (and if necessary write) the container 6, that is to say the data files 2 which it contains, as deposited at the initiative of the sending Ai users .

After decryption, the data files 2 can be stored locally by the recipient user B.

At the end of the decryption, the recipient user B can send (automatically or on external command) to 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 for after reception, by the system 1, of the decryption notification.

In this way, memory space is freed up within the file server 5, which facilitates the subsequent creation of new containers 6.

The method (and the system) which has just been presented offers a certain advantage in terms of safety compared to the known methods (respectively the systems). In fact, during the archiving phase, the data in files 2 cannot be read

- nor a fortiori modified - by the sending A users or by the receiving B user. Any impersonation of any of them is ineffective since it is necessary to have the private key of user B to decrypt the container 5 6B.

We can even see that the control exercised by the sending A users on the container 6 (that is to say on the data files 2 to be shared) ceases at the expiration of the T1 writing delay, even though its content is not yet accessible for the recipient user B 10. The delay (predetermined) with which the recipient user B accesses the data files 2 shared by the sending users Ai makes any dialogue between them in real time impossible, to the benefit of the parsimony with which the users exchange data with each other. This in particular results in an optimization of the bandwidth necessary, in networks, for exchanges between users.

Claims (9)

1. Method for sharing files (2) of computer data between N sending users (Ai) (N an integer, N> 2; i an integer such as 1 <i <N), and a recipient user (B), via a computer system (1) equipped with: A communication server (4), At least one file server (5), and A database (7) of profiles 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 minus a 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); This process being characterized in that it comprises, at the level of the system (1), three successive phases: A writing phase, which includes the operations of: o Receive from a user (A1) master sender a request containing an instruction to create a container (6) of data to share, an identifier (IDAi where i> 2) of each user (Ai where i> 2) sender and an identifier (IDB) of the recipient user (B); o Create the container (6) in a file server (5); o Associate the container (6) with the corresponding profile (IDB), in the database (7), with the recipient user (B); o Associate with the container (6) a predetermined writing delay (T1); o As long as the writing delay (T1) has not expired, allow each sending user (Ai) write access to the container (6); An archiving phase, which includes the operations of: o At the end of the writing delay (T1), prohibit the sending users (Ai) from access, at least in writing, to the container (6); o Encrypt the container (6) using the public key (ZB) of the recipient user (B) to form an encrypted container (6B); o Associate with the encrypted container (6B) a predetermined archiving time (T2); o As long as the archiving period (T2) has not expired, store the encrypted container (6B) in a file server (5) by preventing access to at least the recipient user (B); A sharing phase, which includes the operation consisting, at the end of the archiving period (T2), in allowing the recipient user B to download the encrypted container (6B) in order to decrypt it using his private key (BZ). 2. Method according to claim 1, in which the writing delay (T1) is defined by the master transmitter user (A1). 3. Method according to claim 1, in which the writing delay (T1) is defined automatically. 4. Method according to one of claims 1 to 3, wherein the archiving time (T2) is defined by the user (A1) master transmitter. 5. Method according to one of claims 1 to 3, wherein the archiving time (T2) is automatically defined. 6. Method according to one of the preceding claims, wherein the container (6) is subdivided into several spaces (6.i) own memories, each allocated to a respective user (Ai) transmitter. 7. Method according to one of the preceding claims, which comprises the reception, by the communication server (4), of a decryption notification of the container (6) by the recipient user (B). 8. The method of claim 7, which comprises destroying the encrypted container (6B) on the file server (5) after receipt of the decryption notification by the recipient user (B). 9. Computer system (1) which, for implementing the method according to one of the preceding claims, comprises: A communication server (4), At least one file server (5), and A database (7) of profiles 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, This system (1) further comprising a control unit (8) comprising a programmable memory containing instructions for operating: A writing phase, which includes the operations of: o Receive from a master sending user (A1) a request containing an instruction to create a container (6) of data to be shared, an identifier (IDAi where i φ 1) of each user (Ai where i * 1) sending and an identifier (IDB) of the recipient user (B); o Create the container (6) in a file server (5); o Associate the container (6) with the corresponding profile (IDB), in the database (7), with the recipient user (B); o Associate with the container (6) a predetermined writing delay (T1); o As long as the writing delay (T1) has not expired, allow each sending user (Ai) write access to the container (6); An archiving phase, which includes the operations of: o At the end of the writing delay (T1), prohibit the sending users (Ai) from access, at least in writing, to the container (6); o Encrypt the data of the container (6) using the public key (ZB) of the recipient user (B) to form an encrypted container (6B); o Associate with the encrypted container file (6B) a predetermined archiving time (T2); o As long as the archiving period (T2) has not expired, store the encrypted container (6B) in a file server (5) by preventing access to at least the recipient user (B); A sharing phase, which includes the operation consisting, at the end of the archiving period (T2), in allowing the recipient user (B) to download the encrypted container (6B) in order to decrypt it on using his private key (BZ).