FR3081065A1 - SECURE METHOD AND SYSTEM FOR DELAYED DATA SHARING BETWEEN SEVERAL USERS AND SEVERAL USERS. - Google Patents

Abstract

Method of sharing files (2) between several users (Ai) transmitters and several users (Bk) recipient, which includes: - Writing: ○ Create, at the initiative of a user (A1) master transmitter, a container (6) data associated with the recipient users (Bk); ○ 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); ○ Copy the container for each recipient user (Bk) and encrypt each copy using the public key (ZBk) of each recipient user (Bk); ○ During an archiving delay (T2), store each encrypted container (6Bk); - Sharing: allow each recipient user (Bk) to download the encrypted container (6Bk) for decryption using his private key (BkZ).

Description

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

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

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 >> here designating 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).

To exchange data of large volume (that is to say of size greater than 10 MB), it has become customary to use specialized platforms, e.g. 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 a sending user and P (P an integer, P> 2) recipient users, via a computer system equipped:

From a communication server,

At least one file server, and

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

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 other sending user and an identifier for each receiving user;

o Create the container in a file server;

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 Make a copy of the container for each recipient user, by associating each copy with the corresponding profile, in the database, with the recipient user;

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

o Associate each 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 write time can be set by the master sending user, or automatically.

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

The archiving period can be defined separately for each 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.

Provision may be made for the reception, by the communication server, of a decryption notification of the container by each receiving user. In this case, it is advantageously provided for the destruction of the container on the file server after receipt of the decryption notification by the recipient user.

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

This system comprising a control unit comprising a writable 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 other sending user and an identifier for each receiving user;

o Create the container in a file server;

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 Make a copy of the container for each recipient user, by associating each copy with the corresponding profile, in the database, with the recipient user;

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

o Associate each encrypted container with a predetermined archiving period;

o Until the archiving period has expired, store the encrypted container in a file server by prohibiting it

access at least to the recipient user; A phase of sharing, which includes the operation consisting, at expiration of archiving period, to allow at the user recipient of download the encrypted container in seen from the

decrypt using their 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 (N an integer such as N> 2; i an integer such as 1 <i <N) and P recipients Bk recipients (P an integer such as P> 2; k an integer such as 1 <k <P). 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 with users Ai and Bk).

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, PBk of users in memory. In this case, the database contains at least one PAi profile associated with each sending Ai user, and a PBk profile associated with each receiving Bk user.

Each PAi, PBk user profile includes at least one IDAi, IDBk identifier linked to the respective user Ai, Bk (eg a name, an email address, a telephone number) and at least one respective public cryptographic key ZAi, ZBk .

To this public cryptographic key ZAi, ZBk corresponds a respective private cryptographic key AiZ, BkZ.

The private cryptographic AiZ, BkZ key associated with each user Ai or Bk is stored locally in a 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 master sending user A1 a request containing an instruction to create a container 6, an identifier IDAi (i> 2) from each other sending user Ai (i> 2), and an identifier IDBk from each user Bk recipient;

o Create container 6 in a file server 5;

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 user A1 master transmitter, 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 his own memory space 6.i do not affect the data files 2 deposited by another user Sender Aj (an integer such as I have) in his 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 Make a copy of container 6 for each recipient Bk user, associating each copy with the corresponding IDBk profile, in the database 7, of the recipient Bk user;

o Encrypt each copy of container 6 using the public ZBk key of the recipient user Bk to form an encrypted container 6Bk;

o Associate with each encrypted 6Bk container a predetermined T2 archiving period;

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

FIG. 4 illustrates the obtaining of two containers 6Bk, 6BI (I an integer such as I ψ k) encrypted using, respectively, the public keys ZBk, ZBI of two users Bk, Bl separate recipients having each their respective BkZ, private BIZ key.

The T2 archiving period (shown schematically in the drawings by a second countdown) can be defined by the user A1 master transmitter, 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.

The T2 archiving period can be defined separately for each recipient Bk user.

According to a preferred embodiment, the control unit 8 is devoid of instructions for communicating to each recipient user Bk, during the archiving phase, the very existence of a container 6 or a container 6Bk encrypted to its attention, so that the actual users associated with the recipient Bk users are kept in the dark about this existence.

A third phase, known as sharing, includes the operation consisting, at the end of the T2 archiving period, in allowing each recipient user Bk to download the encrypted container 6Bk in order to decrypt it using their key Private BkZ.

Concretely, the control unit 8 is for example. programmed to send to the recipient user Bk (in particular via the communication server 4) a notification of availability of the encrypted container 6Bk. This notification advantageously contains an IDA1 identifier associated with the user A1 master transmitter, or an IDAi identifier associated with each user Ai transmitter. The download is then preferably ordered by the recipient user Bk, rather than carried out automatically on command from the control unit 8. At least the knowledge of the IDA1 profile of the user A1 master sender (and preferably of the IDAi profiles of all the sender users) by the recipient user Bk can constitute for the latter an index of confidence of the origin and / or of the safety of the data shared by the sending Ai users.

Concretely, each encrypted container 6Bk is sent, on command from the control unit 8, to the corresponding recipient user Bk via the network 3. The decryption is carried out locally by the recipient user Bk, using his key Private BkZ stored locally. The recipient user Bk 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 user Has transmitter.

We have illustrated in FIG. 4 the sending of the two encrypted containers 6Bk, 6BI to the two respective recipients Bk, Bl: we see that each recipient user Bk, Bl performs the decryption using his private key BkZ, BIZ respective to access the files 2.

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

At the end of the decryption, each recipient Bk user 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, provision is advantageously made for the destruction of the corresponding encrypted container 6Bk on the file server 5 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). Indeed, during the archiving phase, the data in files 2 cannot be read - nor a fortiori modified - by any of the sending Ai users or by any of the receiving Bk users. Any impersonation of any of them is ineffective since it is necessary to have the private key of the recipient user Bk to decrypt the container 6Bk.

We can even see that the control exercised by the sending Ai users over the container 6 (that is to say over the data files 2 to be shared) ceases at the expiration of the writing delay T1, even though its content is not yet accessible for any recipient Bk user. The delay (predetermined) with which the recipient users Bk accesses the files 2 of data shared by the sending users Ai makes any dialogue between them impossible in real time, 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 (10)

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 P receiving users (Bk) (P a integer such as P> 2; k an integer such as 1 <k <P) 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, PBk) associated respectively with the users (Ai, Bk), each profile (PAi, PBk) comprising at least one identifier (IDAi, IDBk) and at minus a public cryptographic key (ZAi, ZBk) to which a private key (AiZ, BkZ) 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 (IDBk) of each recipient user (Bk); o Create the container (6) in a file server (5); 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 Make a copy of the container (6) for each recipient user (Bk), associating each copy with the corresponding profile (IDBk), in the database (7), of the recipient user (Bk); o Encrypt each copy of the container (6) using the public key (ZBk) of the recipient user (Bk) to form an encrypted container (6Bk); o Associate with each encrypted container (6Bk) a predetermined archiving time (T2); o As long as the archiving period (T2) has not expired, store the encrypted container (6Bk) in a file server (5) by prohibiting access to at least the recipient user (Bk); A sharing phase, which includes the operation consisting, at the end of the archiving period (T2), in allowing the recipient user (Bk) to download the encrypted container (6Bk) in order to decrypt it on using his private key (BkZ). 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, in which the archiving time (T2) is defined separately for each recipient user (Bk). 7. 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. 8. 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 each recipient user (Bk). 9. The method of claim 8, which comprises destroying the encrypted container (6Bk) on the file server (5) after receipt of the decryption notification by the recipient user (Bk). 10. 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, PBk) associated respectively with the users (Ai, Bk), each profile (PAi, PBk) comprising at least one identifier (IDAi, IDBk) and at least one public cryptographic key (ZAi, ZBk) to which a private key (AiZ, BkZ) 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 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 (IDBk) of each recipient user (Bk); o Create the container (6) in a file server (5); 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 Make a copy of the container (6) for each recipient user (Bk), associating each copy with the corresponding profile (IDBk), in the database (7), of the recipient user (Bk); o Encrypt each copy of the container (6) using the public key (ZBk) of the recipient user (Bk) to form an encrypted container (6Bk); o Associate with each encrypted container (6Bk) a predetermined archiving time (T2) 5; o As long as the archiving period (T2) has not expired, store the encrypted container (6Bk) in a file server (5) by prohibiting access to at least the recipient user (Bk); A sharing phase, which includes the operation consisting, at the end of the archiving period (T2), in allowing the recipient user (Bk) to download the encrypted container (6Bk) in order to decrypt it at using his private key (BkZ).