WO2019215492A1

WO2019215492A1 - Secure method for the delayed sharing of data between a sender user and a recipient user, with local creation of a container

Info

Publication number: WO2019215492A1
Application number: PCT/IB2019/000341
Authority: WO
Inventors: Jonathan Attia; Fabrice LHOMME; Raphaël LOUISET
Original assignee: Lapsechain Sa
Priority date: 2018-05-09
Filing date: 2019-05-07
Publication date: 2019-11-14
Also published as: FR3081063A1; FR3081063B1

Abstract

Disclosed is a method for sharing files (2) between a sender user (A) and a recipient user (B), said method involving three phases: - writing: ◦ at the sender user (A) end, locally creating a data container (6) assigned to the recipient user (B); ◦ during a writing time (T1), allowing the sender user (A) to write into the container (6); - archiving: ◦ transmitting the container (6) to a remote computer system (1); ◦ 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); - 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 for delayed data sharing between a sending user and a recipient user with local creation of a container The invention relates to the field of computing, and more specifically the sharing of computer data files between a user issuer 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).

To exchange large volume data (that is, larger than 10 MB), 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 that 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.

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

For this purpose, there is provided a method of sharing computer data files between a sending user 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 process comprises three successive phases:

A write phase, which includes the operations of:

o Create locally at the sending user's level a container of data to be shared, associated with an identifier of the recipient user; o Associate with the container a predetermined delay of writing;

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

An archiving phase, which includes the following operations: o At the expiration of the write delay, transmit the container to the computer system;

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 delay has not expired, store the encrypted container in the 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:

Since the sending user is distinct from the recipient user, the associated profiles in the profile database for the sending user and the receiving user are distinct.

The writing delay is advantageously defined by the sending user.

The archiving time can be set by the recipient user, or automatically.

Before it is transmitted to the computer system, the container is advantageously encrypted, at the level of the sending user, using his private key. In this case, at the level of the computer system, the container encrypted using the private key of the sender user is first decrypted with the public key of the latter before being re-encrypted. help from the recipient's public key.

It can be 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 advantageously provided for destruction of the container on the file server after receiving the decryption notification by the recipient user.

Other objects and advantages of the invention will appear 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 various steps of the method of the invention.

FIGS. 1 to FIG. 3 show a computer system 1 intended to allow the sharing of computer data files 2 between a user A transmitter and a user B recipient. 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) network. 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 communication sessions (preferably secure) with users (including users A and B).

The computer system 1 comprises, secondly, a file server 5.

The computer system 1 comprises, thirdly, a database 7 of profiles which contains in memory PA profiles, PB users. In this case, the database contains at least one PA profile associated with the user A issuer, and a profile PB associated with the user B recipient. Each PA Profit, User PB includes at least one IDA, IDB linked to the user (eg a name, an email address, a phone number) and at least one public ZA, ZB cryptographic key.

To this key ZA, public cryptographic ZB corresponds to a cryptographic key AZ, private BZ.

The private cryptographic key AZ, BZ associated with each user A or B is stored locally in a memory space thereof.

According to a particular embodiment, the user A issuer is distinct from the user B recipient. In this case, the profiles PA, PB associated, in the database 7 of profiles, to the user A transmitter and the user B recipient, are distinct (it is the same for their keys ZA, ZB public - and their keys AZ, BZ private - respective.

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 sending user A includes a memory space in which directories or "containers" 6 of data files to be shared can be created. In these containers 6 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 operations intended to allow the sharing of the files 2 between the sending user A and the receiving user B are grouped into three phases.

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

o Create locally at the transmitting user A a container 6 of data files 2 to share, associated with an IDB identifier of the user B recipient;

o Associate with the container 6 a predetermined delay T1 write; o As long as the writing delay T1 has not expired, allow the sending user A write access to the container 6. These operations are advantageously controlled by means of a local application implemented in the user A transmitter.

During the write phase, the sending user A is allowed to modify the container 6 by adding or subtracting data files 2. These data files 2 can come from the user A transmitter itself, or be downloaded from remote servers via the network 3.

The writing delay T1 (schematized on the drawings by a first countdown) is advantageously defined by user G A transmitting the writing delay T1 can also be automatically defined by the local application.

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

o At the expiration of the writing delay T1, transmit the container 6 to the computer system 1;

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 the file server 5 by prohibiting access at least to the user B recipient.

In practice, when the writing delay T1 expires, the sending user A sends the computer system 1, via the network 3, the request for transmission of the container 6. This request passes through the communication server 4, which performs the identity checks of the sending user A, typically by comparison of information communicated by the latter (eg a password) with information associated with his IDA profile as stored in the database 7 . As soon as the user A transmitter is identified, access is given to it (possibly by another communication channel, as shown in FIG. 1) to the file server 5.

According to a preferred embodiment, before its transmission to the computer system 1, the container 6 is encrypted by the user A transmitter by means of its private key AZ, so that it is impossible for any entity that does not have the public key ZA of the user A transmitter, to decrypt the container 6. This operation secures (of course temporarily and insufficiently) the container 6. Once received the container 6, the system decrypts it (preferably immediately) using the public key of the user A transmitter (stored in his profile PA), to re-encrypt it to using the public ZB key of the user B recipient.

The archiving time T2 (schematized on the drawings by a second countdown) can be defined by the user A issuer, 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 one 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 an IDA identifier associated with the user A transmitter. 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 IDA profile of the sending user A 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 user A issuer.

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, by via its private BZ key stored locally. The user B recipient can then access read (and if necessary write) to the container 6, that is to say the data files 2 it contains, as filed at the initiative of the user A transmitter.

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 container 6 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 which has just been presented offers a certain security advantage compared with known methods (respectively systems). Indeed, during the archiving phase, the data files 2 can not be read - or even modified - by the sending user A or the user B recipient. Any impersonation of any one of them is inoperative since it is necessary to have the private key of the user B recipient to decrypt the container 6B.

It can also be seen that the control exercised by the user A transmitting on the container 6 (that is to say, on 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 the user B recipient. The (predetermined) delay with which the recipient user B accesses the shared data files 2 by the user A transmitter makes it impossible to communicate with each other in real time, to the benefit of the parsimony with which the users exchange data between themselves . This results in particular an optimization of the bandwidth required, in networks, exchanges between users.

Claims

1. Method for sharing files (2) of computer data between a user (A) transmitter and a user (B) recipient via a computer system (1) equipped with:

A communication server (4),

At least one server (5) of files, and

A database (7) of profiles data containing in memory associated profiles (PA, PB) for the users (A, B), each profile (PA, PB) comprising at least one identifier (IDA, IDB) and less than a public cryptographic key (ZA, ZB) to which a private key (AZ, 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 three successive phases:

A write phase, which includes the operations of:

o Create locally at the sending user (A) a container (6) of data to be shared, associated with an identifier (IDB) of the user (B) recipient;

o Associating with the container (6) a predetermined delay (T1) of writing;

o As long as the writing delay (T1) has not expired, allow the sending user (A) write access to the container (6); An archiving phase, which includes the operations of: o At the expiration of the writing delay (T1), transmitting the container (6) to the computer system (1);

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 timeout (T2) has not expired, store the encrypted container (6B) in the file server (5) 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 delay (T2). using his private key (BZ).

2. Method according to claim 1, wherein, the user (A) transmitter being distinct from the user (B) recipient, the profiles (PA, PB) associated in the database (7) of profiles data, to the sending user (A) and the receiving user (B) are distinct.

The method of claim 1 or claim 2, wherein the write delay (T1) is defined by the sending user (A).

4. Method according to one of claims 1 to 3, wherein the delay (T2) archiving is defined by the user (A) issuer.

5. Method according to one of claims 1 to 3, wherein the delay (T2) archiving is automatically defined.

6. Method according to one of claims 1 to 5, wherein before its transmission to the system (1) computer, the container (6) is encrypted, at the user (A) transmitter, using his private key (AZ).

7. Method according to claim 6, wherein, at the level of the computer system (1), the container (6) encrypted using the private key (AZ) of the user (A) issuer is first decrypted using the public key (ZA) of the user (A) issuer before being re-encrypted using the public key of the user (B) recipient.

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 the recipient user (B).

9. The method of claim 8, which comprises destroying the container (6B) encrypted on the server (5) files after receiving the decryption notification by the user (B) recipient.