FR2929792A1 - METHOD FOR SAVING / RESTORING FILES IN A PAIR NETWORK. - Google Patents

Abstract

The present invention relates to a method for saving at least one file recorded by a peer in the terminal memories of a plurality of nodes of a peer-to-peer network (1), in which: - this peer is allowed to select a list of files to be backed up, - one creates for each file several fragments of data (FB) and a fragment of description (FBL) listing the fragments FB, - one generates for each fragment FBL of description a key of location of the fragment and an encryption key of this fragment FBL, - the FB fragments and the FBL fragments are saved in the terminals of a peer-to-peer network - at least one protected access source fragment (9) for locating and decrypting at least part of the FBL fragments and, - the source fragment (9) is stored in the memory of at least one terminal of the network.

Description

The subject of the present invention is a method for backing up / restoring files in a peer-to-peer network (hereinafter referred to as P2P). A P2P network is a network composed of a set of entities called peers, interconnected with each other. Each of these entities can play both the role of server and client and it participates in the P2P service offered by the supply of some of its resources (hard disk, processor, ...) to the system. The invention applies more particularly to information backup systems in P2P networks based on the use of a distributed hash table (DHT) and fragmentation of files.

Distributed hash table refers to a data structure that associates for each peer a unique identifier that is the result of a hash function applied for example to its IP address or machine name. Similarly, for each resource saved in the P2P network, there is associated a unique key of the same length as the peer identifiers. This key designated below by DHT or CDHT key is calculated by applying a hash function on an element of the resource, such as its name or content. Subsequently, each resource is saved in the peer whose identifier is closest to its key, according to a fixed distance function. Batten, K. Barr, A.Saraf, and S.Trepetin pStore: a secure peer-to-peer backup system and Landers, H. Zhang, and KL Tan PeerStore are known to be better performing by relaxing in peer. -to-peer backup examples of such backup systems. In such systems, a peer fragments each file into several pieces of data called FB (File Block), and generates, for each of these files, an additional fragment called FBL (File Block List) that describes the list of FB fragments that make up the file. file and their location in the P2P network. The FBL fragment also contains additional information for recovering any version of the file. This FBL fragment is also saved in the P2P network and its location is identified by a DHT key.

With the pStore and PeerStore systems, it is sufficient to store for each file its name and its path to be able to determine the DHT key and the decryption key of the fragment FBL associated with the file. From a FBL fragment, the P2P system derives all the DHT keys and encryption keys associated with the FB fragments of the file; it then extracts the data fragments from a P2P network file and reconstructs the entire file. Also known by the website www.dispairse.point6.net is another backup system in a P2P network. In this example, each file saved in the P2P network consists of a set of fragments FB and a single fragment FBL 10, as shown in Figure 1. On the latter, it was assumed that two versions 20 and 21 d same file are saved. The fragment FBL 10 defines for each version of the file and for each FB fragment a key for locating the FB fragment, in the example considered a DHT key (CDHT), and a key for decrypting the FB (CC) fragment and the length of the FB fragment. With known backup systems, it is necessary to restore a file to know the DHT key for locating the FBL fragment, the key to decrypt this FBL fragment in order to retrieve any version of the file. These two keys are found from the file name, its path and a secret relative to the user (password or private key). FIG. 2 shows a method of restoring a file saved in the P2P network with the known backup systems. The user must, from a terminal 3, specify the name and the path of the desired file in order to have access to the fragment FBL 10, this fragment FBL 10 allowing access to fragments FB 11 making it possible to reconstitute the searched file 13 With such backup systems, restoring N files assumes N identical and repeated FBL fragment extraction operations. The publication L.P. Cox, C.D. Muray and B.D. Noble 25 Pastiche: Another backup system defining its own file system and allowing the automatic backup and restore only of a file tree. This system associates for each file or directory a metadata file describing its contents. During the restoration phase, it is sufficient to recover the metadata of the root folder so that it can subsequently retrieve the entire file tree. The publication J. Cooley, C. Taylor and A. Peacock ABS also discloses a system comprising a local database, duplicated itself in the P2P network, to keep the information necessary for restoring the files. . Thus, during the restoration phase, the user accesses his local database or retrieves it entirely from the P2P network to determine the list of data fragments needed to restore a file.

There is a need to further improve the methods for backing up and / or recovering automatically and securely personal files saved in a P2P network. The invention aims to meet this need. According to one of its aspects, the subject of the invention is a method for saving at least one file recorded by a peer in the terminal memories of a plurality of nodes of a peer-to-peer network, in which : - this peer is allowed to select one or more files to be backed up, - one creates for each file several fragments of data (FB) and a fragment of description (FBL) listing the fragments of data, - one generates for each fragment FBL a key for locating the FBL fragment in the network and a key for decrypting this fragment, - the fragments (FB) and the fragments (FBL) are saved in the terminal memories of a peer-to-peer network 20 - on generates at least one protected access source fragment for locating and decrypting at least a portion of the FBL fragments and, - saving the source fragment in the memory of at least one terminal of the network. By memory, it is necessary to understand any type of data storage device, for example hard disk, magnetic tape, optical disk, electronic memories of the FLASH type, among others. By terminal means for example a camera, a camera, a mobile phone, a smartphone, set-top box (for example of the box type connected to ADSL and providing telephone, internet and television), a computer, a portable computer 30 , a refrigerator, an oven, an alarm, a video recorder, an FTP server, a database server, an email server, a workstation or a digital personal assistant.

The invention makes it possible, thanks to the source fragment, to add a level in the hierarchy of the fragments FBL and FB of the prior art. The source fragment, by making it possible to locate and decrypt at least a portion of the description fragments of several files, enables the par to locate and decrypt fragments of these files saved in a single operation. Unlike systems of the prior art, the peer no longer needs to memorize for each FBL fragment the key for locating the latter in the network and / or its decryption key. The invention makes it possible, as soon as the source fragment is accessed, to be able to extract at one time files it automatically backs up in the P2P network, without having to request one by one the files it wishes to extract, which can be particularly useful in case of loss, either by crash or by theft, of the hard disk of the peer terminal. The restoration of the backed up files depends only on the access to the source fragment, it can be done from any terminal of the network, and not only since the one from which the files to be restored have been saved. When generating the source fragment, a key for encrypting the source fragment and a key for locating the source fragment can be computed.

The source fragment can be saved in the memory of one or more nodes of the network, or even in the memory of a secure element of the network, as a backup server set up by an operator. The source fragment may directly contain the keys for locating and decrypting the FBL fragment (s), which may further simplify the decryption and localization of this fragment or fragments from the source fragment. The key for locating the source fragment can be calculated by hashing at least one peer associated with the peer. This key is for example a DHT key. This key being dependent on a secret of the user, for example a password, a private key or a secret code associated with a terminal of the peer, for example a PIN code of a mobile phone the invention can make it possible to prevent any node that does not know this secret from accessing the source fragment, thus making it possible to restrict access to the source fragment at the peer that has saved the files. The key for encrypting the source fragment can be calculated according to at least one secret associated with the peer, for example according to a password, a private key or a secret code. The calculation function makes it possible, for example, to construct a symmetric encryption key from a string of characters by redistributing bits, deleting or adding other bits. The use of such a key to encrypt the source fragment may make it possible to prevent another node, for example by a scanning technique of network backup servers, from reading and interpreting the source fragment to determine the list. backed up files and / or know who owns them. The secret from which is calculated the key for encrypting the source fragment is for example the same as that from which is calculated the key to locate this source fragment.

The invention, by using keys to locate and encrypt the source fragment as mentioned above, makes it possible to condition the access to the source fragment and consequently the determination of the list of files that have been saved in the P2P network and / or their recovery to the knowledge by a node of the key for decrypting the source fragment and the key to locate it. The invention can thus make it possible to respect the privacy of the incumbents of the nodes of the network. The method may comprise a step allowing the peer to select at least one property to be saved by file stored in the memory of a terminal of the network. These properties to be backed up are, for example, the access rights of local users, the creation date of the file or the path to this file.

The checksum of the file (checksum) to check the integrity of the file after it has been restored can also be saved, which can detect errors during the file restore, these errors can be caused by a collision between FB fragments. The method may include the step of allowing the peer to modify a source fragment already generated to take into account: the saving of a new file stored in the memory of a terminal of the network and / or the deletion of a BACKGROUND OF THE INVENTION According to an exemplary implementation of the invention, the source fragment makes it possible to locate and to decipher all the generated FBL fragments, which can allow a peer to have only one source fragment from which it can, if he wishes, restore all the files he has saved.

According to another example of implementation of the invention, several source fragments can be generated, each source fragment making it possible to locate and to decipher part of the FBL fragments associated with the files saved, which can make it possible to associate a source fragment with group of files saved. A key for locating or encrypting a source fragment can be calculated in the same way as previously defined. Keys for locating and encrypting source fragments may differ from one source fragment to another, which can help prevent a node with knowledge of source fragment keys from gaining access to other fragments sources, but also collisions between source fragments.

Files can be grouped into a particular source fragment depending on their type, content, or access rights. File types according to the invention are, for example, photos, videos, sound recordings or texts. Still according to this exemplary implementation of the invention, a root fragment for locating and decrypting the source fragments can be generated, this root fragment can be saved in the memory of at least one P2P network terminal. Another object of the invention is, according to another of its aspects, a method of restoring at least one file saved in the terminal memories of a peer-to-peer network in the form of data fragments (FB) to which is associated a fragment of description (FBL) listing the data fragments, this fragment FBL being localizable and decryptable by a protected access source fragment saved in the memory of a terminal of the network, in which method: - a peer accesses the source fragment from any terminal of the network to determine the list of files saved in the network, - the peer selects at least one file to be restored in the list, - the peer initiates the process of automatic restoration of the selected file (s) from this terminal. The method may comprise a step of updating the list of the files saved, for example to take into account the peer backup of a new file in the network or the deletion of a file in the network. include a step of testing availability and integrity on files in the list. These tests can be performed periodically to ensure that the restoration process is operational and may concern only one file, or even more or even all of the files in the list. Another object of the invention is, according to another of its aspects, a method of selective broadcasting of at least one file recorded in the terminal memories of a peer-to-peer network, this file being fragmented into several data fragments. (FB) which is associated with a description fragment (FBL) listing the FB fragments, this FBL fragment being localizable and decryptable by a protected access source fragment 15 stored in the memory of a terminal of the network, in which method it is possible to a client of the network looking for the recorded file and having satisfied a predefined condition the access to the source fragment and the recovery of the searched file. Access to the searched file may be enabled by providing the network client 20 with a key for locating the source fragment and / or a key for decrypting the source fragment. The key to locate and / or the key to decrypt the source fragment is for example specific to each client, which can allow by assigning personal keys to each client to limit the risk of fraudulent access to the file. The method may include a step of testing availability and integrity on the file. This test can be performed periodically to ensure that the broadcast process is operational. Another object of the invention is, according to another of its aspects, a method for saving at least one file recorded by a peer in the terminal memories 30 of a plurality of nodes of a peer-to-peer network, each file being fragmented into a plurality of data fragments (FB) associated with a description fragment (FBL) listing the data fragments, wherein: - at least one source fragment is generated for locating and decrypting at least a portion of the fragments FBL, - it generates, for this source fragment, a key for locating and a key for encrypting the source fragment according to a secret of the user, and - the source fragment is saved in the memory of at least a network terminal. The P2P network can be a home automation private network. In a variant, the P2P network is an enterprise private network, distributed or not on several geographically distant sites. In another variant, the P2P network uses the Internet network. The invention will be better understood on reading the following description, of non-limiting examples thereof, and on examining the appended drawing, in which: FIGS. 1 and 2 illustrate an example of a method BACKGROUND OF THE INVENTION: FIGS. 3 and 4 illustrate backup and file restoration systems according to the invention, FIG. 5 schematically represents an example of a source fragment according to the invention, FIGS. 6 and 7 illustrate an example of a file saving method and an example of file restoration according to the invention, and FIGS. 8 to 16 show examples of application of the invention. FIGS. 3 and 4 show an example of backup by a pair of files 13; according to the invention. Each file 13; For example, it is fragmented into several data fragments (FB) 11 to which is associated a description fragment (FBL) listing the FB fragments, similar to the known systems described above. As can be seen in FIG. 4, the fragments FBL 10i and FB 11a can be recorded in the terminal memories 3 constituting a peer-to-peer network 1, these terminals possibly being different from that of the peer having recorded the files 13; . Although the terminals 3 are shown in the form of computers in FIG. 4, the invention is of course not limited to the use of such terminals, as will be seen later.

According to the invention, at least one source fragment 9 is stored in the memory of a terminal 3 of the network 1, this terminal being in the example described different from the terminal of the peer having recorded the files 13; For security reasons, the source fragment 9 may be stored in the memory of several distinct nodes and / or be recorded in a backup server (not shown). Such a backup server can be set up by an operator or other trusted entity. As can be seen in FIG. 3, the invention makes it possible to add a level of hierarchy to the FBL 10i and FB 11i fragments by virtue of the source fragment 9 which makes it possible to locate and decrypt all the FBL 10 fragments; and, through the latter, the location of all the fragments FB 1 li constituting a file 13; According to this example, the invention makes it possible for the user to no longer necessarily have to memorize an item of information enabling him to retrieve the DHT key and / or the encryption key of one of his FBL fragments.

FIG. 5 shows an example of source fragment 9. This fragment contains different fields. A first field 30 assigns an identifier / number to the file 13; A second field 31 lists the file name 13; checked in. A third field 32 corresponds to a key, for example a DHT key, making it possible to locate the fragment FBL 10; associated with file 13; A fourth field 33 corresponds to a key making it possible to decrypt the fragment FBL 10; associated with file 13; Access to the source fragment 9 is protected by two keys, a key to allow the location of the source fragment 9 in the network 1, for example a DHT key, and a key to enable its encryption in the case of the file backup or its decryption in the case of file restoration or file broadcasting. These keys are determined in the example described from a secret only known to the user and which can take the form of a password, a private key, a secret code such as a code PIN of a terminal, for example a mobile phone or a personal digital assistant belonging to the peer.

The DHT key is for example determined by hashing the password or the private key or the PIN code.

The key for encrypting or decrypting the source fragment 9 is for example calculated according to the password, the private key or a secret code. This calculation function makes it possible, for example, to construct a symmetric encryption or decryption key from a string of characters by redistributing these bits, deleting or adding other bits. The various fragments saved in the network 1 relating to the backup of a file 13; are therefore encrypted: FB 11 data fragments using, for example, the Convergent Encryption method as disclosed in the publication J.R. Sweetness, A. Adya, W.J. Bolosky, D. Simon and M. Theimer Reclaiming space from duplicate files in a serverless distributed file system, fragments FBL 10; using the symmetric encryption key saved in the source fragment 9, and the source fragment 9 using a key calculated from the peer secret. In the case where a node wants to access, without permission, a file 13 ;, it must first determine the keys allowing access to the source fragment 9. These keys being, as mentioned above, determined from of a user secret, no unauthorized node can access the source fragment 9 and therefore the saved files 13; Thus, no unauthorized node can not access a file without the authorization of its owner, nor determine the list of files saved in the network 1. The backup of all the data associated with the peer, both the useful data and the data. metadata, in the network 1, ensures that the process of restoring these files can start, even without a hard disk or in case of crash of the entire hard disk, from any terminal 3 connected to the network 1.

The source fragment 9 may also comprise, as shown in FIG. 5, other fields 34 containing properties of the file 13; saved. These properties concern for example the access rights of local users, the creation date of the file or the file path. Field 34 may also contain a checksum to check the integrity of the entire file after it is restored. This control makes it possible to detect errors due to a collision between FB fragments, these errors being considered negligible.

The method used in backup systems such as pStore or PeerStore is to separately check the integrity of each FB fragment. This parcel checking of the integrity of a file can be problematic when a collision between fragments occurs, that is, if another different FB fragment but having the same DHT key value is stored instead a fragment of this file. Collision detection is not possible in the case of parcel control, but the collision problem can be detected if the global integrity check on the entire file is performed via the source fragment 9. invention allows the peer to access the source fragment 9 provided to have communicated his secret, namely his password, his private key, his secret code or its PIN code, on the basis of which the keys to locate and to decrypt the source fragment 9 will be determined, then recover all the files that have been saved in the P2P network. FIG. 6 shows an exemplary method of saving files in a network 1 as shown in FIGS. 3 and 4. At a first step 100, the peer selects the list of files it wishes to save in the network 1. A in step 110, the peer selects one or more properties to be backed up, these properties corresponding to those mentioned in relation to the field 34 of the source fragment 9. At step 120, the peer specifies the level of importance of the information saved. . In step 130, the fragments FB1 li are created by applying the necessary security processing and saved in the network 1, and a fragment FBL 10i is associated for each file 13; saved. At step 140, the peer generates for each FBL fragment 10; a location key and an encryption key, decrypts the fragment and the backup in the network 1. In step 150, a source fragment 9 is generated with calculation of keys for locating and encrypting this source fragment 9.

In step 160, the peer saves this source fragment 9 in the network 1 in the memory of one or more computer terminals 3 of the network and / or in the memory of a backup server. FIG. 7 shows an example of a method for restoring by a peer one or more files saved according to the invention, this restoration method being able to be performed from any terminal 3 of the network and not only from the terminal with which the For example, par has performed the method shown in FIG. 6. In step 200, the user presents the secret that he used to associate an encryption key and a location key with his source fragment 9.

In step 210, the peer retrieves and decrypts the source fragment 9. In step 220, the peer determines the list of files 13; saved in the network 1. The visualization of these files can be in the form of a flat list of file names, or a tree highlighting the path originally occupied by each file saved.

In step 230, the peer selects the number of files it wishes to restore, namely one, several or all of the files 13; In step 240, the automatic restoration of this or these files begins with the recovery of its fragment FBL 10i and its data fragments FB l li. A peer can also recover its source fragment 9 to take into account the saving of a new file in the network 1 and / or the deletion of a file from the network 1 and / or to perform availability and integrity tests on one or more files saved 13 ;, so as to ensure, periodically or in a controlled manner by the user, that the backup method is operational. Several examples of applications of the invention will now be described with reference to FIGS. 8 to 16. FIG. 8 shows an example of application of the invention to a home automation private network 1. This network 1 comprises, for example, a plurality of smart appliances and / or electronic devices such as a home appliance. photo, a camera, a mobile phone, a set-top box, a computer, a refrigerator, an oven, an alarm, a video recorder, these devices each having a memory and corresponding to computer terminals 3; within the meaning of the invention. All or part of these devices can communicate by carrier or non-wired link, for example Bluetooth or Wifi type. By creating a peer-to-peer network 1 whose nodes are made up of these different devices, a user can create his own distributed file recovery system. Indeed, it can keep a copy of the important files of a node, for example the computer 31 or 32, on the other nodes of the P2P network in order to recover them in case of loss of the original files due to the loss of the hard disk of the terminal 31 or 32. According to this example, the invention makes it possible to benefit from a new, free and normally reliable restoration system, the nodes being under the entire control of the user. In the example described, the different nodes of the network 1 can share the same source fragment, which makes it possible to recover, thanks to the source fragment, any file from any node, independently of the node from which the file has been registered.

FIG. 9 shows another example of application of the invention to produce a system for restoring files in a corporate private network 1, including servers, for example FTP servers, database servers. or email servers, and workstations that correspond to terminals within the meaning of the invention, constitute a peer-to-peer network.

In this example, the free disk spaces of the memories of the various terminals 3 are used to record files, making it possible to duplicate the important data of a node on the other nodes of the network 1 in order to restore them in case of loss of the initial files. The invention allows the company to benefit from a file restoration system: - free, the company does not need to reserve a particular server to duplicate the important data of its various terminals 3, - reliable, all the nodes being under the entire control of the company and, - sure, the terminals 3 being in this example servers and workstations of the company, these different machines are always available in the network, so the Backing up and restoring a file in Network 1 can be done at any time.

The example of FIG. 10 differs from that of FIG. 9 in that the enterprise is distributed on several geographically distant sites in which local intranets 11, 12 and 13 similar to the network described with reference to FIG. . In the example of FIG. 10, communication between local intranet networks of two remote geographical sites is secured by establishing a VPN tunnel 2 created by one of the following protocols: Layer Two Tunneling Protocol (L2TP), IPsec (Internet Protocol) Security) or MPLS VPN. The invention, by making it possible to save node files of a geographical site in memory nodes of other geographical sites, allows the restoration of these files even in the case where the geographical site in which is located the terminal of the node having saved the files would disappear in its entirety due for example to a fire, a natural disaster or an attack. In the example of FIG. 10, the company assigns, according to a first embodiment, to each geographic site a single source fragment 9 enabling the automatic restoration of all the important data of a site. The secret allowing access to this source fragment is preferably known only by the site manager. According to a second embodiment, the company allocates for each service of each geographical site, for example the financial or commercial service of each geographical site, a single source fragment. In this example, the source fragment allows the automatic restoration of all the important data of a service and its secret is advantageously known only by the director of the service. According to a third embodiment, the company assigns each terminal 3 a source fragment 9. In this example, the source fragment 9 only allows the automatic restoration of important data of a particular terminal and its secret is advantageously known. than the owner of this terminal. FIG. 11 shows another example of application of the invention. In this example, the peer-to-peer network 1 is formed by nodes that are terminals 3 connected to the Internet. In this example, the terminals 3 are chosen from computers, mobile phones, set-top boxes (for example of the box type connected to ADSL and providing telephone, internet and television) and digital personal digital assistants.

In this example, a peer keeps a copy of its important data in the disk spaces of the memories of the terminals of the other nodes of the network 1, in order to recover them in case of loss of its local data. If desired, a mobile or fixed operator, an access provider, or a new P2P service provider may charge the proposed backup and restore service to the peer. In this example application, if the user is the owner of a single node, a single source fragment allowing him to automatically restore from any node, all of his data already saved in the network 1 10 can be assigned. Still in this application example, if the user is the owner of several nodes, he can choose between: - sharing a single source fragment between his different nodes. Thus, it is possible for it to automatically restore all its files already saved in the network 1 independently of the node from which the file backup took place; - assign each of its nodes a different source fragment. In this case, the automatic recovery process will be restricted to the files of a single node, - assign each of its nodes a different source fragment and create a root fragment to locate and decrypt the source fragments specific to each of them. his knots. In this case, the automatic recovery process can include all files already backed up in network 1 or be restricted to files of a single node; To ensure the proper operation of the backup and / or restore method, the network 1 may comprise, as represented in FIG. 12, a central confidential entity 5 in periodic communication with all the nodes 3 of the network 1 and arranged for: avoid the selfish behavior of nodes by counting, for example, the resources provided and consumed by each node. A credit or debit billing system may be provided depending on whether the resources provided are more or less important than the resources consumed; - control access to the proposed P2P service; - control the behavior of the different nodes during the operation of the system, by periodically checking that each node performs the assigned work, that it is available, that previously saved fragments are always well saved and intact. This allows for example to evaluate the reliability level of a node, on which could be based the billing associated with a node; - ensure a good quality of service to users. To allow the authorization of a peer to perform a backup and / or restore method according to the invention, several solutions are possible: - use of a specific home automation box so that all the networked equipment of the house can to benefit from it; - software in the specific mobile allowing to save only the data of this mobile; - passing through a proxy service provider, allowing the peer to access and restore its data regardless of the host machine (mobile, PC ...); 15 - obligation to have an access token signed by a trusted node which is responsible for controlling access to the proposed service; - obligation to have access to a particular node of the network, access being restricted to only entities authorized to make P2P service. Access to the source file may be controlled by a mobile or fixed operator, an access provider or a P2P service provider. The access control may for example consist of an AAA (Authentication, Authorization, Accounting) control device. This particular node can then be responsible for controlling the good behavior of the nodes during the various backup operations but also in the duration. The invention is not limited to backing up and / or restoring files backed up in a peer-to-peer network. According to other applications, it allows the selective broadcast in a peer-to-peer network of at least one file, for example a multimedia or musical content, for example one or more films or music files, game software, professional or other, stored in the memory of at least one terminal of the network. By diffusion of the secret allowing calculation of the DHT and decryption keys associated with the source fragment 9 to a group of users, it is possible, thanks to the invention, to distribute data to this group of users, which can to make it possible to obtain the equivalent of a virtual server, insofar as the files to be distributed are saved in the memories of different terminals. FIG. 13 shows such an example of application of the invention. A node 6 of the network 1, hereinafter referred to as the server node acts as a server distributing films, multimedia content for example, other nodes 8 of the network 1, hereinafter called clients. Unlike a centralized video on demand server, it is not thanks to the invention not necessary to use a DNS name or a large storage space. According to the example shown in FIG. 13, the server node 6 firstly saves in the memories of the terminals 3 of the network all the films 13; to share with the clients of the network 1. The server node 6 then calculates from a secret the location key and the encryption key for access to the source fragment 9 listing the set of films 13; saved then creates and saves its source fragment in the memory of any terminal of the network 1.

The server node 6 then transmits the secret allowing access to the source fragment to any client 8 of the network 1 having satisfied a predefined condition, for example the subscription to a subscription. The dissemination of the secret allowing access to the source fragment can take several forms.

By the knowledge of the secret, a client 8 can retrieve and decrypt the source fragment 9 of the server node 6 and thus determine the list of films that are available. Moreover, from the information contained in this source fragment, it can recover any film 13; already saved by the server node in the network 1. Although the data of the server node 6 is saved in the terminal memories 3 of different nodes of the network, only the nodes having access to the source fragment 9 can access the films 13; . To share a new movie, the server-node 6 can save it in the network 1 and then update its source fragment 9. By recovering the new version of this source fragment, a client 8 can determine the new list of films offered by the server node 6.

The server node 6 can, at any time, remove films from the network 1, for example in order to free disk space in the memories of the terminals 3 to save new movies. According to this example, the invention makes it possible to have an accessible service even if the server node 6 is inaccessible since all the necessary information is saved and distributed on the various nodes of the P2P network. The secret allowing access to the source fragment 9 can be distributed to the clients 8 in several forms: a password or PIN code: the same string of characters is communicated to the clients. This string is to be entered in the access software to the data distribution application. a secret, such as a private key, communicated to the customers on a protected physical medium, for example an electronic chip or a USB key. a custom client-dependent secret, being determined according to certain characteristics of this client, for example the MAC address of the terminal that it uses. The user downloads a client software to which he must enter the personalized secret. The software can then calculate the secret allowing access to the source fragment according to this personalized secret. The personalized secret can still be determined using other characteristics of the customer, such as his subscriber number when he subscribes to an operator. The communication of the secret allowing access to the source fragment or, where appropriate, the personalized secret can take the following forms: - communication of the secret by mail or postal mail, - downloading by the client software of the secret with a server in 25 line. Downloading from the server can be considered almost transparent for the user. In addition, the client software can provide a serial number or a client name so that the server controls the dissemination and personalization of the secret, - download by the user of the secret from an online server. After having authenticated with this server, the user downloads the secret, for example, and accordingly configures his client software.

In a variant, the file to be broadcast is a file relating to an advertisement or of an informative nature and the server node 6 may broadcast the secret to all the clients 8 of the network 1 having made the request. The modification rights of the source fragment, to add or delete a new saved file, can be reserved to the server node 6 in order to prevent a client to whom the secret has been revealed can not modify the saved contents. This control of these rights of modification of the source fragment can be ensured by a centralized server in which are memorized all the source fragments of the network, and which grants the rights of modification only to the node-waiter 6 and gives the right In another example of an application, the invention allows the sharing of files between the nodes of the network 1 by the knowledge of a source fragment 9. The principle is identical to the principle of diffusion of data. a file by a server node 6 to a client 8 described above, except that the modification rights of the source fragment are open to all the nodes of the network. The same services are possible, namely the secret access control of the source fragment 9, the updates of the source fragment 9, and the management of the different versions of the saved files 13; The invention may also allow the creation of a root fragment for locating and decrypting a plurality of source fragments 9 saved in the network 1.

In the example shown in FIG. 14, the root fragment 7 makes it possible to locate and decrypt first source fragments 9a, the latter making it possible to locate and to decipher second source fragments 9b which are similar to the source fragments described with reference to FIGS. preceding. In this example, access to each source fragment 9a or 9b is conditioned by the knowledge of a secret according to the examples described above. The secret is different from a first source fragment 9a to another, as well as from a second source fragment 9b to the other. Thus, access to a single source fragment only allows the recovery of a subset of files. Only the access to the root fragment 7, conditioned for example by the knowledge of a secret making it possible to calculate keys to locate and decipher the root fragment, can allow the access to all the source fragments and the complete recovery of the files saved in the network 1. In this example, the first source fragment 9a1 contains keys for locating and decrypting the second source fragments 9b1, 9b2 and 9b3, which makes it possible to locate and decrypt the fragments FBL 101 to 105 and 107, and therefore, access to the files 131 to 135 and 137. According to this example, the invention can allow the peer having saved the files whose restoration is allowed through access to the root fragment 7 to broadcast only a subset files to a network client. If this client can, according to the example of FIG. 14, access only the second source fragment 9b1, it can only recover the fragments FBL 101 to 103 and consequently only recover the files 131 to 133. According to this example , the peer may decide to share only a subset of files that it has backed up with other nodes in the network. The peer may choose to share only the files 135 and 137 with one or more nodes of the network by sending them the secret allowing them to access only the second source fragment 9b3. Still according to this example, the invention also makes it possible to optimize the volume of disk space of the memory of the terminals 3; by allowing several first source fragments 9a to point to one and the same second source fragment 9b, or even to a plurality of same second source fragments 9b. In the same way, several second source fragments 9b can point to the same FBL fragment 10, or even to several same FBL fragments. FIG. 15 shows an example of application of the invention in which two root fragments 71 and 72 associated with two different pairs point to the same source fragment 90. This source fragment 90 allows, for example, access to the set of files shared between the two peers. Thus, each of the peer having access to the root fragment 71 and the one having access to the root fragment 72 can be considered as the owner of the source fragment 90 and the files to which access is thus allowed, although these files are only saved. only once in the network. The peer having saved the files whose access is allowed by the root file does not need to retain the secrets allowing access to the different source fragments or, when the source fragments are hierarchized into first and second source fragments, the secrets allowing access to these different source fragments, but only that of the root fragment, the latter advantageously containing the secrets allowing access to the source fragments.

In the case of the example of FIG. 14, if a server node 6 wishes to allow a client to access all the files it has saved in the network, it is sufficient to communicate to it the secret allowing access to the root fragment 7, in this way it will be able to obtain the list of the first source fragments 9a, allowing themselves access to the second source fragments 9b. FIG. 16 shows an example of a method for distributing the files saved within different source fragments 9. In the example represented, for each type of backup file, a source fragment 9 is associated. The source fragment 91 is not for example relative to files containing photos, which allows the peer to restrict its automatic restoration to all of its photos that have been saved in the network 1. In another example, we group together the files saved according to their content. For example, a server-node offering video films can associate to each category of films (cultural, sport, ...) a source fragment 9. Subsequently, a customer can subscribe to a particular category of films by asking the secret allowing access to said source fragment 9. In another example, the files saved are grouped according to the access rights by the nodes of the network to the files saved. For example, private files are associated with a source fragment whose secret can never be transmitted to the other nodes of the network, and public files are associated with another source fragment whose secret can be transmitted to all the nodes of the network. Because of the property of optimization of the volume of memory disk space previously described, the invention can make it possible to group the files saved in a database of multi-criteria source fragments, the number of source fragments and hierarchy of source fragments, to know first, second ... n'e source sources increasing with the number of criteria. The invention is of course not limited to the examples which have just been described. For example, characteristics described with reference to various embodiments of the invention may be combined.

Claims (23)

REVENDICATIONS1. A method of saving at least one file (13;) recorded by a peer in the terminal memories (3;) of a plurality of nodes of a peer-to-peer network (1), wherein: this peer to select a list of files to be backed up, - for each file (13;) is created several data fragments (FB) (l li) and a description fragment (FBL) (10i) listing the fragments FB, - one for each description fragment FBL (10;) generates a key for locating the fragment and an encryption key for this fragment FBL (10i), - the fragments FB (1i) and the fragments FBL (10i) are saved in the terminals (3;) of a peer-to-peer network - generating at least one protected access source fragment (9) for locating and decrypting at least a portion of the FBL fragments (10i) and, - saving the source fragment ( 9) in the memory of at least one terminal (3;) of the network. 2. Method according to claim 1, wherein during the generation of the source fragment, a key is computed for locating the source fragment and a key for encrypting the source fragment. 3. Method according to the preceding claim, wherein calculating the key for locating the source fragment (9) by hashing at least one secret associated with the peer. 4. The method of claim 2 or 3, wherein calculating the key for encrypting the source fragment (9) according to at least one secret associated with the peer. 5. Method according to one of the two immediately preceding claims, wherein a secret associated with the peer is selected from a password, a private key, and a secret code associated with a terminal of the peer. 6. A method according to any one of the preceding claims, wherein the peer is allowed to select at least one property to be saved by a file stored in the network terminal memories. 7. Method according to the preceding claim, wherein said at least one property is selected from the checksum of the file (checksum) and / or the date of creation of the file and / or the access rights to the file and / or the file path and / or file version. A method as claimed in any one of the preceding claims, wherein the peer is allowed to specify the level of importance of the saved file. 9. Method according to any one of the preceding claims, in which the peer is allowed to modify a source fragment (9) already generated to take into account: the saving of a new file (13;) in the terminal memories ( 3;) network and / or delete a saved file. 10. Method according to any one of the preceding claims wherein the source fragment (9) makes it possible to locate and decipher all the generated FBL (10i) fragments. 11. Method according to any one of claims 1 to 9, wherein generating several source fragments (9), each source fragment (9) for locating and decrypting part of the generated FBL (10;) fragments. 12. Method according to the preceding claim, wherein for each source fragment (9), two keys are calculated, one for locating and the other for encrypting the source fragment (9). 13. The method according to the preceding claim, wherein the keys for locating and encrypting the source fragment (9) differ from one source fragment to another. 14. Method according to one of the two immediately preceding claims, wherein the files (13;) are stored in a particular source fragment (9) according to their type, content or access rights associated therewith. 15. Method according to any one of claims 11 to 14, wherein a root fragment (7) is generated for locating and decrypting the source fragments (9) and in which this root fragment (7) is saved in the memory. at least one terminal (3;) of the network. 16. A method for selectively broadcasting at least one file (13;) stored in the memory of at least one terminal (3;) of a peer-to-peer network (1), said file (13;) being fragmented into several fragments of FBI data (1 li), to which is associated a description fragment (FBL) (10;) listing the fragments (FBL) (1li), these FBL fragments (10i) being localizable and decryptable by a source fragment (9) ) with protected access stored in the memory of a terminal of the network, in which method a client (8) of the network searching for the recorded file (13;) and having satisfied a predefined condition is allowed access to the source fragment (9 ) and the recovery of the searched file. 17. Method according to the preceding claim, wherein access to the searched file (13;) by providing the client (8) of the network a key for locating the source fragment (9) and / or a key for decrypting the source fragment (9). 10 18. The method according to the preceding claim, wherein the key for locating and / or the key for decrypting the source fragment is customer-specific (8). 19. Method according to any one of claims 16 to 18, comprising a step of testing the availability and integrity of the file sought. 20. A method for restoring at least one saved file (13;) in the terminal memories (3;) of a peer-to-peer network in the form of data fragments (11i) with which a description fragment is associated (10i) listing the fragments of data, this description fragment being localizable and decrypted by a protected access source fragment (9) stored in the memory of a terminal of the network, in which process: a peer accesses the source fragment (9) for, from any terminal of the network, determining the list of files saved in the network - the peer selects at least one file to be restored (13;) in the list, - the peer initiates the automatic recovery process of the selected files from this terminal. 25 21. Method according to the preceding claim, comprising a step of updating the list of saved files. 22. Method according to one of the two immediately preceding claims, comprising a step of testing availability and integrity on files listed in the source fragment. 30 23. A method of saving at least one file (13;) recorded by a peer in the terminal memories (3;) of a plurality of nodes of a peer-to-peer network, each file being fragmented into several fragments of data (11i) to which is associated a description fragment (10;) listing the data fragments, in which method: - at least one source fragment for locating and decrypting at least part of the description fragments is generated, - generating for this source fragment (9) a key to locate and a key for encrypting the source fragment (9) according to a secret of the user, and - the source fragment is saved in the memory of at least one network terminal. 10