The present invention relates to a method, and the related system, of distribution of digital contents over a telecommunication network, in particular the Internet network, that allows in a simple, reliable, robust, and safe way, to distribute digital contents through a decentralised network architecture, such as for instance multimedia contents, the method being inexpensive, increasing contents retrievability, and being substantially unaffected by possible network failures.

So far, distribution of free and commercial digital contents over the Internet network has been entrusted to Client/Server systems, wherein a user visits, through the browser running on his/her own computer (operating as client), a distribution site operating as server, chooses the product, and requires the contents to the server that directly sends it to the browser of the client computer.

In Client-Server distribution systems, all the digital contents are stored in one or more central Servers from which users may both download the product and making purchase transactions.

In commercial-type systems, the distribution has been flanked by another technology that allows to manage, control and/or limit the use of contents by the user who downloads them. These technologies, known with the name of Digital Rights Management Systems or DRMSs, have allowed the implementation of commercial models which have obtained a particular success in distributing musical pieces over the Internet, all based on Client/Server architectures. In substance the content is encrypted at the source and when the user requires for it the related licence is distributed simultaneously as it is, which licence allows it to be correctly decoded and used.

However, these systems suffer from some drawbacks.

In fact, this Client-Server distribution architecture in any case entails a significant effort with regard to managing and maintenance costs, since as the users increase performances drastically fall because the same servers actually constitute a bottleneck. In order to make up for such situation companies are forced to invest in new serving stations, with all the problems concerning their update and synchronisation. This involves considerable expenses because they have to be sized for critical

situations, which are not much frequent but which have to be managed by the system. There is often a situation wherein many both computational and passband resources, are wasted.

Recently, a new technology for distribution of contents has been developed, that is called "peer-to-peer" or "P2P" as well, based on a decentralised network architecture developing among several computers, operating as network nodes (also called peers or hosts), which connect with each other. In the application to distribution of digital contents, the P2P architecture is commonly used for sharing resources, so that transmission directly occurs among nodes, being often normal home computers, which put the contents of at least one portion of its own hard- disk memory at everyone's disposal. In other words, each single user of the system contributes as an network active node that may be dynamically used also as server node for another user who has made a request for that. Practically, a sharing folder exists on each computer wherein the files which are desired to be distributed are stored, and each user is capable to simultaneously download from one or more other users a particular digital content (of any type) that the integrated search engine is able to find. In this scenario no central server exists that receives requests and sends data, but each network node is simultaneously contents distributor and consumer.

P2P systems differs from each other in communication protocols, search algorithms, and network structure, which elements determine performances. In particular, different types of P2P architecture exist. A first type, called first generation one, is the P2P network with a simple search server: when a user enters the network he/she connects to the main server, that offers directory services by providing for a list of users. The type of second generation is the "pure" P2P network, that is based on a wholly decentralised system wherein there exists no central server but only nodes: when a user enters the network he/she connects to any one of the nodes (called "Entry-Point") and exchanges shared resources and services. Those belonging to the type of third generation, wholly decentralised as the preceding one, are P2P protocols (called DHT, Distributed Hash Table) in which the logic structure of the network remains practically constant, independently from the number of nodes making it up, and techniques for routing searches of contents are based on metrics defined in the set of node identifiers.

In these architectures, each computer contributing to the network as a node, besides the possibility of serving files, may have, depending on the type of P2P network, the responsibility of passing data related to the network maintenance, as it is in a pure P2P, as Kazaa or Gnutella, or in a second or third generation one. This scheme eliminates the need for traditional servers and allows a network to operate even if some nodes fall, since it does not depend on any central server. For the end user, the strong feature distinguishing all the types of P2P architectures from Client/Server systems is the download speed, because a digital content may be simultaneously downloaded from a plurality of peers, and the optimisation of the band that is exploited at its best, thanks to the possibility of having in a certain instant a plurality of nodes operating as servers.

The decrease in costs of high speed Internet connections, combined with availability of powerful personal computer with network functionalities (also called "network-ready" ones), has allowed P2P network to be developed on a global scale. Moreover, the total lack of mechanisms controlling the distributed contents (it is possible to let in and retrieve any product, either legal or not) has allowed a large growth of users on such network.

However, systems of distribution Peer-to-Peer developed so far suffer from some drawbacks due substantially to the lack of efficient and reliable mechanisms for controlling the distributed contents.

The consequence thereof is the lack of any guarantee about source and quality of what is downloaded, that causes the phenomenon of fakes, i.e. of files having a content different from the one expected as described in the name.

Moreover, such technologies are often used in pirate distribution wherein producers' and authors' rights are absolutely not protected.

It is therefore an object of the present invention to allow the distribution of digital contents, such as for instance multimedia contents, over a telecommunication network, in particular the Internet network, in a simple, reliable, robust, safe, and inexpensive way, the distribution being fast and substantially not affected by possible failures over the network.

It is specific subject matter of the present invention a method of distribution of one or more copies of digital contents to one or more users

0328

4 over a telecommunication network, in particular the Internet network, wherein one or more serving computers or servers store for each digital content at least one file, a plurality of processing devices of users being capable to connect through said telecommunication network to said one or more servers, the method being characterised in that, for each digital content, the first distributed copy of said at least one corresponding file is transmitted by said one or more servers to a processing device of a first user, and in that the copies which are distributed after the first one are transmitted according to a decentralised network architecture of the type "Peer-to-Peer" or "P2P" comprising one or more nodes or distributor peers, which transmit at least one portion of said at least one corresponding file to at least one processing device of at least one second user, which include at least one server and/or one or more processing devices of one or more users who have previously received said at least one file. Always according to the invention, said plurality of processing devices of users may comprise computers and/or PDAs and/or mobile phones.

Preferably according to the invention, the copies of said at least one corresponding file distributed by said one or more servers to one or more processing devices of one or more users are transmitted according to a "P2P" protocol.

Still according to the invention, for at least one digital content said at least one corresponding file may be an encrypted file, said one or more servers storing data capable to generate at least one corresponding digital licence, capable to decode said at least one corresponding encrypted file.

Furthermore according to the invention, said one or more servers may transmit to a processing device of a user, who purchases a digital content, said at least one corresponding digital licence, capable to decode the copy of said at least one corresponding encrypted file received from the processing device of the purchasing user.

Always according to the invention, the transmission of said at least one corresponding digital licence by said one or more servers may be successive or simultaneous to the reception of the copy of said at least one corresponding encrypted file by the processing device of the purchasing user.

Still according to the invention, before the transmission of said

at least one corresponding digital licence by said one or more servers, the processing device of the purchasing user may connect to said one or more servers for looking up at least one catalogue of digital contents capable to be distributed, and it may purchase said digital content by making a financial transaction.

Furthermore according to the invention, preliminarily to the distribution of the first copy of said at least one corresponding encrypted file of a digital content, transmitted by said one or more servers to a processing device of a first user, said one or more servers may receive at least one corresponding original file of said digital content, and they may encrypt it generating said at least one corresponding encrypted file, that is stored along with said data capable to generate at least one corresponding digital licence.

Always according to the invention, preliminarily to the distribution of the first copy of said at least one corresponding encrypted file of a digital content, and after the storing of said at least one corresponding encrypted file and of said data capable to generate at least one corresponding digital licence, said one or more servers may insert in said at least one catalogue information capable to be looked up and/or to allow said processing device of the purchasing user to purchase said digital content.

Still according to the invention, said at least one corresponding encrypted file may be obtained according to a technique of digital rights management coding or DRMS (Digital Rights Management System). Furthermore according to the invention, said digital contents may comprise at least one textual content and/or at least one video content and/or at least one audio content and/or at least one multimedia content and/or at least one software application.

Always according to the invention, said one or more servers may monitor and/or may determine, for each one of said distributed copies, the related transmission carried out by said one or more processing devices of one or more users which have previously received said at least one file operating as distributor peers.

Still according to the invention, for each one of said copies distributed after the first one, said one or more servers may receive, from said at least one processing device of said at least one second user, information related to the amount of data received by said at least one

processing device of said at least one second user from said one or more processing devices operating as distributor peers, and they may further receive, from each one of said one or more processing devices operating as distributor peers, information related to the amount of data that it has transmitted to said at least one processing device of said at least one second user, and they may determine, for each one of said one or more processing devices operating as distributor peers, a value indicating the offered service in the transmission of said copy distributed after the first one. Always according to the invention, said one or more servers may process at least one portion of the information received from said at least one processing device of said at least one second user and/or at least one portion of the information received from each one of said one or more processing devices operating as distributor peers and/or information related to said at least one file, preferably comprising information related to the size of said at/least one file, and they may assign a reliability index to each one of said one or more processing devices which have operated as distributor peers.

Still according to the invention, said one or more servers may assign to each one of said one or more processing devices which have operated as distributor peers a remuneration proportional to the corresponding value indicating the offered service.

Always according to the invention, said remuneration may be weighed on the basis of said reliability index corresponding to the respective processing device that has operated as distributor peer.

Furthermore according to the invention, said one or more servers may assign said remuneration after having transmitted to said at least one processing device of said at least one second user said at least one corresponding digital licence. Always according to the invention, at least one processing device of a user may connect to said one or more servers for indicating an availability to operate as distributor peer, said one or more servers transmitting to said at least one processing device a list of one or more files, each one corresponding to at least one portion of said at least one file corresponding to a digital content, said at least one processing device receiving a copy of each one of said one or more files included in the list.

Still according to the invention, at least one processing device

of a user may connect to said one or more servers for inserting in a wish- list one or more digital contents, said at least one processing device receiving, for each one of said one or more digital contents included in the wish-list, at least one part of a copy of said at least one corresponding encrypted file.

Furthermore according to the invention, said one or more servers may be connected to one or more external servers through one or more application interfaces, said one or more servers recognising as certified one or more processing devices of users which are certified for said one or more external servers.

Always according to the invention, said one or more servers may send on request to said one or more external servers at least one catalogue of digital contents, the encrypted files and the digital licences of which are stored by said one or more servers, so that a processing device of a user certified for said one or more external servers is capable to connect to said one or more external servers for looking said at least one catalogue up and to purchase a digital content included therein by making a financial transaction with said one or more external servers.

Still according to the invention, said one or more servers may send to said one or more external servers information related to said assigned remuneration to each one of said one or more processing devices of one or more users certified for said one or more external servers which have operated as distributor peers.

It is still specific subject matter of the present invention a system of distribution of one or more copies of digital contents to one or more users over a telecommunication network, in particular the Internet network, comprising:

- one or more servers storing for each digital content at least one file, said one or more servers being capable to be connected to said telecommunication network,

- a plurality of processing devices of users capable to connect through said telecommunication network to said one or more servers, the system being characterised in that it is capable to operate according to the previously described method of distribution of one or more copies of digital contents.

Always according to the invention, said one or more servers may comprise at least one server of the contents, that stores for each

digital content at least one file of which it transmits the first distributed copy.

Still according to the invention, at least one file is an encrypted file, said one or more servers storing data capable to generate at least one corresponding digital licence, capable to decode said at least one corresponding encrypted file.

Furthermore according to the invention, said one or more servers may comprise at least one server of the licences, that stores said data capable to generate at least one corresponding digital licence, it generates said at least one corresponding digital licence, and it transmits it to the processing device of a purchasing user.

Always according to the invention, said one or more servers may comprise at least one server of the products that receives at least one corresponding original file of a digital content, it encrypt it generating said at least one corresponding encrypted file, it sends said at least one corresponding encrypted file to said at least one server of the contents, and it sends said data capable to generate at least one corresponding digital licence to said at least one server of the licences.

Still according to the invention, said one or more servers may comprise at least one look-up server to which a purchasing user connects for looking up at least one catalogue of digital contents capable to be distributed, and for purchasing said digital content making a financial transaction.

Furthermore according to the invention, said at least one server of the products may send to said at least one look-up server information to insert in said at least one catalogue.

Always according to the invention, the system may further comprise one or more application interfaces which connect said one or more servers to one or more external servers. The present invention will now be described, by way of illustration and not by way of limitation, according to its preferred embodiments, by particularly referring to the Figures of the enclosed drawings, in which:

Figure 1 schematically shows a preferred embodiment of the system according to the invention and the operations performed for publication and first purchase of a digital content;

Figure 2 shows the system of Figure 1 and the operations

performed for a purchase of a digital content following the first one;

Figure 3 schematically shows a second embodiment of the system according to the invention and the operations performed for downloading the encrypted files of a list of digital contents indicated by the system servers;

Figure 4 schematically shows a third embodiment of the system according to the invention and the operations performed for downloading the encrypted files included in a wish-list indicated by the user; and

Figure 5 schematically shows a fourth embodiment of the system according to the invention.

In the Figures, alike elements are indicated by same reference numbers.

The method and the system of distribution according to the invention are based on an innovative type of P2P decentralised network architecture, similar to the one of pure P2P systems for shared files. In particular, the system according to the invention is capable to manage also the so called digital rights, by separating the moments of content distribution from related licence distribution.

The system of distribution according to the invention is substantially a software architecture composed by Client/Server applications and a client side application capable to connect to a P2P type network.

The publication of a product, i.e. of a digital content, exclusively occurs through some servers of the system according to the invention, that, in this way, is capable to control the validity of the contents and to properly encrypt them according to the specification required by the DRMS technology associated with the file type (text, video, audio, multimedia, software application). In particular, the architecture of the system according to the invention allows to integrate different types of DRMS, allowing protection during distribution of different content types.

Figure 1 schematically shows the system according to the invention and the operations performed for publication and first purchase of a product.

First of all, the producer sends the product file 1 to a server 2 of the products. The product server 2 preferably encrypts the file 1 and sends the encrypted file 1' to a server peer 3 of the contents, that represents the first entry point for the distribution towards the nodes or client peers of the

network on which the system is based. In particular, the content server 3 distributes the product files towards the network client peers through P2P protocol. The product server 2 also sends the data 4 for generating the licences to a server 5 of the licences, which data are necessary for afterwards generating the licences which will allow the buyers to decode the encrypted files V. The product server 2 further sends catalogue information 6 to a web server 7, accessible by the users via Internet, that then inserts the new product, corresponding to the file 1 , into the catalogue of the available products. A user may look the catalogue up via web, through his/her own computer 8 that connects to the web server 7, and in this phase he/she may purchase the product, completing a financial transaction according to one of the conventional techniques (for instance through credit card, debit card, electronic wallet, or prepaid card). In particular, in other embodiments of the system according to the invention the web server 7 may actually comprise two or more servers, each of which provides at least a part of the product catalogues or manages the purchase activities. Furthermore, the web server 7 (or the corresponding catalogue/purchase servers) may be (either directly or through a suitable computer connected to the same) accessible by user devices different from computers 8, such as, for instance, PDA and mobile phones.

The first copy of the encrypted file 1 ' of the product is sent by the content server peer 3 to the buyer's computer 8. At the completion of download of the encrypted file 1', the licence server 5 sends to the buyer's computer 8 the purchased licence 9, that will allow the buyer to decode the encrypted file 1' and to enjoy the corresponding product.

In particular, communications among the computer 8 and the system servers are controlled by a client application residing onto the computer 8 and by server applications residing onto several system servers.

The system of Figure 1 is reliable and flexible. Moreover, the centralised control of the catalogue, of the payments, of reporting, and of the licence delivery ensures a very high safety in distributing the digital contents, equivalent to the Client/Server systems, since all the product files circulating over the network are protected (i.e. they are encrypted files 1') by DRMS technology. In particular, the system operates in Multi-Drm way, supporting several commercial DRMSs for distributing different

product types.

The system according to the invention also provides for a remuneration of the users contributing as peers to the distribution of the digital contents. In fact, considering that in the P2P architecture each user is both client and server of a content residing onto his/her own computer, the system according to the invention is provided with accurate techniques of auditing and reporting, which monitor, for each purchase made by a purchasing user, the percentages of content which a user operating as distributor server offers to the purchasing user. In particular, by cross- checking the distribution data which the computers of the purchasing user, operating as client, and of the distributor users, operating as servers, communicate to the group of the system servers (preferably, but not exclusively, to the licence server 5), the system is capable to detect the presence of possible anomalies and to assign to each user a remuneration proportional to the service that he/she has offered.

In fact, the group of the system servers receives from the purchasing user's computer the information related to the amounts of data received from the distributor users' computers, and from each computer of the distributor users the information related to the amount of data which it has transmitted to the purchasing user's computer. Afterwards, by examining and comparing the information with each other and with the information related to the size of the encrypted file 1' received by the purchasing user's computer, the group of the system servers is capable to recognise a possible falsification of the information which the single computers of the users have provided, by assigning a corresponding reliability index to each user. On the basis of such reliability index and of the information related to the amount of data transmitted to the purchasing user's computer, the system remunerates each distributor user.

This remuneration technique may be advantageously used in a system implementation of the type of on-line store, in order to motivate the users to redistribute the purchased products. In any case the distribution techniques subject of the present invention are effectively independent from it. In other contexts, for instance within a company, content distribution modes could be implemented without the benefit of the remuneration technique.

A first embodiment of the system according to the invention causes each user, who has already wholly downloaded onto his/her own

computer the encrypted file 1' of a digital content following a purchase thereof, automatically becomes distributor for such content. With reference to Figure 2, wherein the system servers 2, 3, 5, and 7 are represented by a group 10 of servers, it may be observed that a purchasing user looks the catalogue up via web, through his/her own computer 8 that connects to the group 10 of servers (namely to the web server 7 of Figure 1), and he/she purchases a product. The computers 11 of users who have previously purchased the same product now operate as distributor peers, sending portions 12 of the encrypted file 1' to the purchasing user's computer 8. At the completion of download of the whole encrypted file Y by this one, the group 10 of servers (namely the licence server 5 of Figure 1) sends the purchased licence 9 to the purchasing user's computer 8, that will allow him/her to decode the encrypted file 1'.

The users whose computers have contributed as distributor peers to the delivery of the encrypted file V to the purchasing user's computer 8 are remunerated proportionally to the offered service, i.e. proportionally to the sum of sizes of the corresponding portions 12 of encrypted file transmitted and/or at the time of connection to the P2P network. With this distribution scheme, the files of the most required/sold products will have a larger capillarity of distribution and hence more sources (computers operating as peers) from which they are downloadable with a related increase of performances during the following phases of download. A second embodiment of the system according to the invention provides that the client applications of the computers of users who give their consent receive from the system servers indications for downloading a set of files, or parts thereof, either encrypted or not. Thanks to this technique, the system is capable to distribute the products on the basis of principles of geographical location (for example, a song in Italian language will be mostly downloaded in Italy and, hence, it is advantageous to distribute it onto the computers of users from Italy) or on the basis of historical statistical analysis, and possibly also before the insertion of the product into the available catalogue, so that before the effective purchases and/or requests of use begin, copies of the files, either encrypted or not, are already distributed in a capillary way within the network. Moreover, this distribution technique allows to increase the retrievability of less distributed

products, thus balancing the performances of download.

Safety, in the cases where it is necessary (i.e. when the files are distributed as encrypted and it is necessary to purchase the related licence for decoding them) remains in any case guaranteed by the fact that the users, who give their consent to reception of encrypted files to redistribute, even if they have not purchased them, cannot use the products until the effective purchase of the related licence.

Figure 3 schematically shows the architecture of such second embodiment of the system according to the invention. In particular, the group 10 of the servers (preferably a component of the web server 7) sends a respective list 14 of the encrypted files to download (possibly only partially, i.e. downloading only one or more parts thereof) to each of the computers 13 of the users who give their consent to operate as distributor peers of not purchased products. The computer 13 search and download the parts of encrypted files 1' listed in the respective list, increasing their retrievability. In particular, such encrypted files V may be downloaded from the content server peer 3 of Figure 1 , or from computers 11 of users who have previously purchased the same product (as shown in Figure 2), or from computers 13 of other users who have given their consent to operate as distributor peers of not purchased products which have already downloaded the encrypted files 1'.

Afterwards all the computers 13 will contribute to the successive distributions as normal distributor nodes. The system of Figure 3 also allows the users who have not purchased products to be remunerated for the redistribution service.

When the user of the computer 13 decides to enjoy the content of a product for which it operates as distributor peer, he/she purchases a licence 9 thereof from the group 10 of servers (by preferably purchasing it from the web server 7 and receiving it from the licence server 5), that allows him/her to decode the encrypted file V already stored into his/her computer 13.

A third embodiment of the system according to the invention allows a user to download the encrypted files of products for which he/she would intend to purchase a licence, but before the effective purchase.

With reference to Figure 4, it may be observed that in this case the user inserts in a proper wish-list, communicated by his/her own

computer 15 to the group 10 of servers (preferably the web server 7), a product that he/she has chosen from the catalogue looked up via web (by accessing the web server 7 of Figure 1) and that he/she wishes to purchase in the future. At this point, all the computers which may operate as distributor peers, i.e. the computers 11 of Figure 2 and preferably also the computers 13 of Figure 3, contribute to the distribution of the encrypted file V corresponding to the product inserted into the wish-list of the computer 15, which downloads it into its memory.

When the user of the computer 15 decides to enjoy the content of a product of his/her own wish-list, he/she purchases a licence 9 thereof from the group 10 of servers (namely by purchasing it from the web server

7 and receiving it from the licence server 5), that allows him/her to decode the encrypted file 1' already stored into his/her computer 15.

All the computers which have contributed as distributor peers of the encrypted file V are remunerated for the offered service, preferably after that the user of the computer 15 has effectively purchased the licence 9.

The system of Figure 4 allows the users to store onto their own computers 15 a digital "media library" ready to use. In the moment at which a user would wish to use a product already present within his/her own wish-list, he/she will only have to purchase the licence 9 thereof, with a substantial reduction to zero of the time lasting from the product purchase and its enjoyment, since the download has already occurred.

Moreover, such system increases the retrievability of products, since also the computer 15 may contribute to the distribution of encrypted files corresponding to products within its own wish-list before the effective purchase of the related licence.

Furthermore, the system of Figure 3 allows the group 10 of servers (preferably the web server 7 of Figure 1) to process an accurate user profiling of the and to make definite and specific promotions even for single users.

Other embodiments of the system according to the invention provide a distribution of the non encrypted files 1 (alternatively to or, more preferably, in combination with the distribution of encrypted files 1', for instance files 1 related to products given as prizes to the system customers). In this case, the system according to the invention ensures that such files, with which a respective identifying code (hash) is

associated, are not false files (fakes), since the applications installed onto the users' computers 8 (or onto other devices such as PDAs and mobile phones) search over the network the files 1 to download corresponding exclusively to the respective identifying code. The system according to the invention is easily integratable with already existing systems of distribution of digital contents. In fact, the system according to the invention is provided with a set of functionalities capable to allow an easy migration of pre-existing commercial web sites based on a Client/Server architecture towards a P2P architecture with possible mechanism of remuneration of the users contributing to the distribution.

To this end, a fourth embodiment of the system is provided with suitable application interfaces operating onto the group 10 of system servers. As shown in Figure 5, all the management of economic transactions always occurs through the servers 20 of the pre-existing external web site, connected to the group 10 of system servers through one or more application interfaces 16.

First of all, the group 10 of system servers according to the invention offers to the external servers 20 the catalogue 17 of the available products through the system according to the invention, (which catalogue is received by the external servers 20 on their request).

A user of the external web site connects through his/her own computer 8' to the external servers 20, he/she looks the catalogue up and purchases a product. In particular, the users certified for the external servers 20 (i.e. authorised to browse in the external web site) are recognised as certified also by the group 10 of servers, a relationship existing between the group 10 (operating as the so called trusting domain) and the external servers 20 (the web site of which operates as the so called trusted domain) that enable the users of the latter to be authenticated by the former.

At this point, all the computers which may operate as distributor peers (i.e. computers 11 of Figure 2, preferably also the computers 13 of Figure 3, and possibly also the computers 15 of Figure 4) and which are authenticated in the external web site, contribute to the distribution of the encrypted file 1', corresponding to the purchased product, to the computer 8'.

Afterwards, the group 10 of servers (namely the licence server 5 of Figure 1) sends the licence 9 to the computer 8', that allows it to decode the encrypted file V and enjoy the content of the purchased product. Finally, the group 10 of the servers processes the remunerations to assign to the users whose computers 11 and/or 13 and/or 15 have contributed to the distribution, and it communicates the related information 18 to the external servers 20.

The separation between distribution of contents, controlled by the group 10 of servers, and management of the electronic wallets of the users, controlled by the external servers 20, ensures the maximum compatibility and the minimum cost of integration of the system according to the invention with external conventional Client/Server distribution systems. The advantages offered by the method and the system of distribution according to the invention are numerous.

First of all, since it is based on a P2P architecture, the invention optimises the typical performances of such networks, maintaining the features of safety of the distribution of contents. Moreover, the elimination of central servers and of the related infrastructure reduces the costs of system maintenance up to 80% with respect to the costs of the conventional Client/Server distribution systems.

Still, the processing and band resources needed by the network automatically adapt to the new requests, since the same users provide to maintain and improve the performances of their own computers, operating as nodes of the distribution network, which thus naturally follow the available technological advancements of the state of the art, with a cost that is null for the person who manages the network (through the group 10 of servers). Furthermore, the method and the system according to the invention ensure a high retrievability of the digital contents, thanks to: the large number of replicas due to the usually high density of nodes and to the strong interchange among them; the tolerance to the network failures, because if a node falls it is automatically replaced with other nodes; the presence of multiple source at zero cost, since each new computer downloading an encrypted file is automatically a new source node for the successive requests.

The preferred embodiments have been above described and some modifications of this invention have been suggested, but it should be understood that those skilled in the art can make other variations and changes, without so departing from the related scope of protection, as defined by the following claims.