EP1396135A1

EP1396135A1 - Method and system of conditional access to ip services

Info

Publication number: EP1396135A1
Application number: EP20020730365
Authority: EP
Inventors: Emmanuel Gouleau; No[L Fontaine; David Girault
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2001-04-19
Filing date: 2002-04-18
Publication date: 2004-03-10
Also published as: CA2444435A1; KR20030092083A; US20040128665A1; WO2002087190A1; JP2004535704A; FR2823936B1; CN1518824A; FR2823936A1

Abstract

A method for transmitting information (20) with an access control via a network (3) using IP-type protocol. According to the invention, upon transmission a first datagram (23) is scrambled; a header (24) is defined, said header comprising at least one item of data identifying the means of access control; said header is concatenated with the first scrambled datagram (23) in order to create a data block (26); the data block is encapsulated in a second IP datagram (30); the second IP datagram (30) is transmitted for reception via the network; the data block (26) is extracted from the datagram thus received; the header (24) is extracted (24); the first datagram (23) is de-scrambled if access to said data is authorized; and the de-scrambled data is delivered.

Description

METHOD AND SYSTEM FOR CONDITIONAL ACCESS TO IP SERVICES TECHNICAL FIELD

The present invention relates to the field of scrambling and controlling access to IP services.

The invention relates more particularly to a method and a system for transmitting / receiving information with access control through a network using the IP protocol as well as a device making it possible to implement the method.

This method can be used to control access to audiovisual streaming services over IP and to data broadcasting services broadcast by satellite over the Internet.

STATE OF THE PRIOR ART

Several solutions are currently used to perform scrambling and access control on IP data. Among these solutions, let us quote the IPSEC standard which allows to confidentially transport data in IP datagrams in point to point mode. This standard offers the following services:

- confidentiality authentication.

- integrity.

IPSEC protection does not require modification of the server or of the application software installed at the client. However, the scrambling is generally applied to all traffic between the client and the server and not just to a specific service. Also, insofar as the traffic includes data which do not require protection, the IPSEC standard cannot be used if one wishes to carry out selective scrambling on specific services.

Another drawback of this standard comes from the fact that it requires the existence of a return channel. However, in the context of a point-to-multipoint application, the return channel is not necessary, for example satellite transmission (multicast in English).

In addition, the exchange of keys allowing access to content is carried out through the use of public key algorithms. Therefore, this standard does not make it possible to condition access to the content of the information by means of the possession of rights such as those defined for digital television for example (pay per view, subscription, etc.) and which are registered. in a security processor.

There is also the SSL (Secure Socket Layer) standard which is an encryption technique applied to data at the transport layer. This technique uses protocol identifiers and port numbers to distinguish protected data from unprotected data. For example, a hyperlink on the network will use this technique if the protocol identifier says "HTTPS" instead of "HTTP". Data protected by SSL generally navigates through a connection to port 443 of the TCP server. Also, if the server receives a connection to port 443, it applies SSL scrambling to this connection and transmits the IP data to the client. This procedure allows the client and the server to distinguish protected data from that which is not.

A drawback of this technique comes from its dependence on the TCP transport protocol used and therefore imposes the data format of this protocol on the data to be scrambled. The object of the invention is to remedy the drawbacks of the prior art described above by means of a method making it possible to scramble services I? a generic way and to control access to these services by means of an access control device such as a memory card.

Another object of the invention is to overcome the constraints linked to the transport protocol.

Another aim is to scramble IP data whatever the application using this data, in particular in the following service configurations:

- Point-to-point services;

- Multipath services with the existence of a “client → server” return channel; - Multipoint services without "client → server" return path.

These aims are achieved by means of a process comprising the following steps: On transmission: - Scramble a first IP datagram; - Define a header comprising at least one piece of data identifying the access control means;

- Concatenate this header with the first scrambled datagram to create a data block; - Encapsulate the data block in a second IP datagram;

- Send this second IP datagram across the network; and

On reception: - extract the data block from the received datagram;

- extract the header;

- descramble the first datagram if access to this data is authorized;

- deliver the descrambled data. According to the invention, the data block is encapsulated in a UDP packet.

According to the invention, the data block is encapsulated directly in an IP datagram.

According to the invention, the scrambling step comprises the following phases:

- Define the services to be confused by a label to which corresponds a source IP address or a destination IP address;

- Enter at least one access condition or at least one secret key.

According to the invention, the data block comprises:

- the header (Access_control_header) conveying the information necessary for the processing by a user terminal of the data transported; and - A sequence (Payload) representing the information to be scrambled. According to the invention, the data block respects the following syntax: CAS_DATA_UNIT () {

Access_control_header () p bytes Payload q bytes

}

According to the invention, the sequence (Payload) respects the following syntax: payload () {data bytes n bytes padding bytes p bytes,

(p can take the value 0)

}

The header also includes a field (EDC) representing an error detection sequence.

According to an embodiment of the invention, in which the data block is inserted in a packet

UDP, which is itself inserted into an IP datagram, in transmission, a source UDP port is allocated dynamically when the UDP link is opened.

In this embodiment, the allocation of the destination UDP port number can be carried out statically (optional configuration data dedicated by a regulatory authority) or else dynamically by a signaling protocol between the scrambler and the descrambler.

According to this embodiment of the invention, the reception of IP / UDP datagrams by the end client comprises the following steps: - receiving the second IP datagram; - receive the UDP packet on the port, previously opened (static or dynamic port);

- recover and descramble the data block;

- extract the header; - send the descrambled IP datagram to a pseudo-driver;

Extract the data from the first Destination datagram; send the extracted packet to the destination application.

According to an alternative in this embodiment, the reception of UDP datagrams by the end client comprises the following steps:

- receive the second IP datagram; - receive the UDP packet on the open port (static or dynamic port);

- recover and descramble the data block;

- extract the header;

- re-transmit the first IP datagram on the loopback address of the IP stack;

- extract the data from the first datagram and send it to the recipient application.

According to the invention, the transmitted IP services are audiovisual streams over IP. According to the invention, the IP services transmitted are data transmitted by satellite via an IP network.

The data are transmitted through an IP network by a transmitter comprising means for associating with the IP datagrams a header comprising at least one datum identifying the access control means and an indication of the scrambling method used. The transmitter according to the invention also comprises:

- means for defining the services to be scrambled by a label to which a source IP address or a destination IP address corresponds; - Means for entering at least one access condition or at least one secret key.

According to the invention, this transmitter comprises an IP data flow server, a gateway comprising an IP scrambler, an ECM generator, an ΞMM generator and a database.

The reception of the data transmitted through the network is carried out by a receiver comprising means for extracting the header from a scrambled datagram and means for activating at least one access condition or at least one secret key.

The scrambling and access control system in an IP type network comprises a transmitter and a receiver as described above.

The IP services scrambling and access control device according to the invention comprises a man-machine interface intended to define the services to be scrambled and to enter the access conditions or secret keys.

According to the invention, the access control means comprise a memory card for transporting the secret key.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge from the description which follows follow, taken by way of nonlimiting example, with reference to the appended figures in which:

- Figure 1 schematically shows a data transmission / reception system with access control according to the invention;

- Figure 2 schematically illustrates the steps of defining the structure of a datagram according to one invention;

- Figure 3 schematically illustrates a preferred embodiment of the scrambling according to

The invention;

FIG. 4 schematically illustrates a first reception mode implemented in the method according to the invention; - Figure 5 schematically illustrates a second reception mode implemented in the method according to the invention;

- Figure 6 schematically shows a system of scrambling data in a point-to-point environment according to the invention.

DETAILED DESCRIPTION OF MODES FOR IMPLEMENTING THE INVENTION

Figure 1 schematically illustrates a system in which several data processing and transmission equipment are interconnected in a local area network 2 (LAN) which is connected, via the internet network 3, to several clients 4. LAN 2 includes an IP data flow server β, a gateway 8 comprising an IP scrambler, an ECM generator 12 (DVB access control message, Entitlement Control Message) EMM 14 (DVB access management message, Entitlement Management Message in English) and a database 16. LAN 2 is connected to a Web server 17. The WEB server 17 indicating the characteristics of the Application server (@IP_server, program_name , scrambling_active) is not necessarily on the same LAN 2.

The IP data delivered by the stream server 6 can be audio visual services requiring the possession of an access right recorded in a memory card held by authorized clients 4. These audio visual services are scrambled by the IP scrambler integrated into the gateway 8 before being transmitted over the internet network 3.

Each client 4 has equipment 18 comprising an access control device such as for example a memory card.

The gateway 8 is provided with an HMI man-machine interface program enabling it: - to define the services to be scrambled; - enter access conditions or secret keys.

The services to be scrambled are identified by a label to which corresponds a source IP address or a destination IP address depending on whether it is desired to scramble the data originating from a source and / or going to a destination. As illustrated by the tables below (Table I and II), the scrambling of the data results from the connection of the service identifier (Idservice), characterized by the source address (s) and / or destination (d) IP datagrams, and a scrambling key. The renewal periodicity of this key is relatively low in systems not using a memory card (table I), and may be higher in systems implementing a card (table II). In these, it is called the control word.

TABLE I

TABLE II

In systems implementing a memory card, obtaining the control word is subject to the possession of rights previously entered in the card.

The signage related to the implementation of the access control system using the memory card to restore the control words in the IP context covers the following services in order of priority: - data broadcasting services using the UDP / IP stack: IPSat (push, file transfer);

- audiovisual broadcasting services over IP (IP multipoint flow) using the UDP / IP stack (videoconferencing or multipoint audioconferencing, audiovisual broadcasting);

- audiovisual consultation services over IP using the UDP / IP stack (VOD, point-to-point videoconferencing, telephony over IP); - transactional services using the stack

TCP / IP.

FIG. 2 schematically illustrates the steps for creating a datagram according to the invention. The data to be transmitted 20 are first cut into packets 21 which can be of variable lengths. Each package

21 is then associated with an IP header 22 to constitute a first IP datagram 23.

Transmission of packets 21 across the network

IP is based on the following principle: - Scrambling of the first IP 23 datagram

(PDU, Data Unit Protocol in English).

- Definition of a header 24 "access_control_header" called "access control signage" making it possible to supply the descrambler with the elements involved in the scrambling operation. This header 24 includes a discriminator 25 identifying the type of access control system implemented to scramble the IP datagram 23, and control data 27. - Concatenation of this header 24 and the IP datagram 23 to form a block of data 26; - Encapsulate this data block 26 in a UDP datagram.

All of these operations are called IP-CAS (IP-Conditional Access System) in the following description.

The general structure of a header 24 is illustrated in appendix 1 describing the different fields representing blocks of binary data. This header 24 includes: - a field (header_length) representing the total length of the header 24;

- a field (payload_scrambling_control) indicating the mode of application of the scrambling in the event of scrambling of the useful information. The header 24 can also include a field (EDC) representing our error detection sequence. According to the invention, if (payload_scrambling_control ≠ 00), the header 24 (Access_control_header) further includes a field (payload_descrambling_way) specifying the descrambling mode of the content of the payload.

If the field (payload_descrambling_way = xi), xi being a binary value, the header 24 also includes a field (ECM_CA_descriptor_flag) indicating the presence of at least one conditional access descriptor (ECM_CA_descriptor) in the header 24 of the datagram scrambled 23, and a field (ECM_flag) indicating, when its value is equal to 1, the presence of at least one ECM field () in the header of the scrambled datagram 23. If (ECM_CA_descriptor_flag ≠ l), the header 24 includes a field (Nb_ECM_CA_descriptor) indicating the number of blocks (ECM_CA_descrιptor) present in this header 24 of the scrambled datagram 23.

The header 24 also includes a field (access_control_header_start_sequence) or making it possible to identify the start of the header, a field (versιon_number) indicating the current version of the header 24, a field (servιce_ID) indicating the reference of the service used, a field (payload_type) indicating the type of data transmitted, and a field (RUFO) reserved for future use.

The header 24 also includes a field

(scramblιng_algoπthm_type) intended to indicate the type of algorithm used to scramble the datagram, and a cna p error corrector (CRC_32) of the descrambled useful data.

If the datagram 23 is scrambled by an algorithm operating in block mode, the header 24 (Access_control_header) also includes:

- a field (payload_paddιng_sιze) specifying the number of stuffing bytes added at the end of the payload;

- a field (IVOperator_ID_length) indicating, when its value is other than zero, the presence and the length of the vector field for initializing the scrambler;

- a field (IVOperator_ID_value) indicating, when the value of (IVOperator_ID_length) is other than zero, the value of the initializer vector of the scrambler, and - a field (RUF1) reserved for future use. The header 24 also includes a field (ECM_CA_descrιptor_flag) indicating, when its value is equal to 1, the presence of at least one conditional access descriptor (ECM_CA_descπptor) in the header 24 of the scrambled datagram 23, a field ( RUF2) reserved for future use.

The header 24 also includes a field (ECM_CA_descrιptor_versιon__number) indicating the version of the block (ECM_CA_descriptor). If (EMM_CA__descπptor_flag = 1), the header 24 includes a field (EMM_CA_descrιptor_vers on_number) indicating the version of the block (EMM_CA_descrιptor) and a block αe data (ΞMM-CA desr.ptor).

If (ECM_flag = 1), the header 24 includes a field (NB_ECM) indicating the number of ECM in the header 24 of the scrambled datagram 23.

If (payload_descramblmg_way ≠ 010), the header 24 includes a third field (RUF3) reserved for future use; The access control message includes:

- an ECM_ιex pointer intended to differentiate several ECMs to select a particular ECM for descrambling;

- an ECM_table table containing the ECM data and the phase change instructions.

As an example, the access control message has the following format: ECM () {

ECM_table () 8 bits} where ECM_index represents the ECM associated with the conditional access descriptor, and

ECM_table (), represents the structure of ECM.

The ECM table includes: - an identification field (table_id)

- a field indicating the length of an ECM, (ECM-length)

ECM_table (), has the following structure: ECM_table () (table_id = 0x80 or 0x81 ^' 8 bits

NOTJSED 4 bit

ECM_length -12 bits

NOTJJSED 8 bit

For (i = G; i <M; i ++) {ECM_data_bytes 8 bits

} where, table_id represents an 8-bit field that identifies the type of data contained in the table; - a field (descriptor_tag) indicating the start of an ECM conditional access descriptor;

- a field (ECM_CA descriptor_length) indicating the length of an ECM descriptor; a field (CA_system_ID) representing an identifier of the access control system used;

- a pointer (ECM_index).

As an example, the conditional access descriptor (ECM_CA_descriptor) has the following format:

ECM CA descriptor () { Descrιptor_tag = 0x09 8 bit

ECM_CA_descπptor_length 8 bits

16-bit CA_system_ID

ECM_mdex 8 bit for (ι = 0; KN; ι ++) {pπvate_data_bytes 8 bit

} and the algorithm type identifier includes: - a CI_tag identifier; - a Cl-length field indicating the length of the identifier; a CI_value field indicating the value of the Cl-tag identifier.

The algorithm type identifier scrambles this in the following format: TO {

CI_tag = 0x13 8 bit

CI_length = 0x01 8 bit

8-bit CI value

The service operator includes:

- an identifier SOID_tag of the block allowing to describe the area of the service operator used in the smart card; - a SOID_length field indicating the length of said zone;

- a SOID_value field indicating the value of the SOID_tag identifier.

The service operator is identified by a field with the following syntax: SOIDO { SOID_tag = 0x14 8 bit

SOID_length = 0x03 8 bit

SOID_value 24 bits

} or

SOID_value represents a field identifying a service area used in the smart card.

Two scrambling options are available: - Systematic scrambling of the downstream; - Scrambling activated by the WEB server 17.

FIG. 4 schematically illustrates the scrambling activated by the WEB server 17 - (step (c)) on the initiative of the client (step (a)). In this case, an active daemon on the WEB server 17 sends an activation request to the IP scrambler (step (b)) on reception of an HTTP request (a) from the client on a link with the “scrambling to activate ”(keyword in the URL ht tp: // @ IP: port / scrambled_program / program_name,). The scrambling scenario is as follows:

1) The flow server 6 sends IP datagrams 23 in point-to-point mode or in Multipoint mode. The destination address of datagrams 23 is that of the client (point-to-point) or else a broadcast address (Multipoint).

2) The IP scrambler optionally filters the IP datagrams 23 whose origin address is that of the flow server 6 and maintains a scrambling session by destination address. This filter acts at the Ethernet level in the diagram in Figure 4. 3) The IP scrambler then concatenates the header 24 (access_control_header) to the IP datagram 23 which is scrambled in step 2 then sends this field on a UDP stack to the same destination address as the initial datagram.

4) Datagrams destined for the β stream server are not intercepted by the IP scrambler.

To perform this scrambling procedure, the equipment performing the scrambling must know the scrambling parameters. Several options are then possible:

- "Wired" information in a table on the IP scrambler;

- Interrogation by the IP scrambler of the dedicated WEB 17 server centralizing the necessary information;

- Update of the IP scrambler by the WEB server 17;

- Local update of the scrambler, made by the operator.

The valuation of the UDP / IP tunnel fields in transmission is carried out according to the following mechanism:

- The scrambler generates an IP datagram with the following information: • The source IP address is the IP address of

1 scrambler. This address is a public IP address.

• The destination IP address is the destination address of the initial datagram. • The source UDP port is allocated dynamically when the UDP stack is opened. The UDP port of the scrambled stream is not the same as the UDP port of the original stream in order to avoid loopback problems on the client computer. There are two possibilities for assigning the destination UDP port number hereinafter called the UDP IP-CAS port:

- Dynamic allocation by a signaling protocol between the scrambler and the descrambler. This assumes the existence of a return path between the client and the server;

- Configuration value dedicated by a given certification authority with the following rules:

- The known ports are the ports of 0 and 1023;

- The registered ports are those from 1024 to 49151;

- The dynamically allocated ports are those from 49152 to 65535.

Reception procedures: “IP CAS” virtual stack A “descrambler” software 35 is installed on the client computer (Windows, Linux, MacOS,). Two implementations are envisaged, either the use of a Pseudo-driver 40, or the use of loopback in "raw" mode. 1 - Use of a pseudo-driver.

Figure 5 illustrates this mode of implementation. The data is received on the interface of the access provider 42 to the internet network 3 (ISP) and forwarded via the IP stack 44 of the client machine to the descrambler 35 awaiting UDP data on the specific port IP_CAS. This descrambler 35 recovers data from the UDP datagram via the IP stack, extract the <dιscπmmateur - access_control_header> header and descramble the original IP datagram.

The descrambler 35 provides the IP datagram to the end client 4 awaiting data on the original destination port.

In order to transmit this IP datagram to the end customer (local to the machine), the network pseudo-driver 40 must be developed under the IP stack: - This pseudo-driver is awaiting data from the descrambler 35 and provides it to the IP stack.

- The final application is waiting on its particular port and normally retrieves the data in clear after unencapsulating the original IP datagram by the IP / TCP or UDP stack.

This solution can be implemented on an operating system allowing the addition of a ^2nd network driver under the IP stack of the machine. The routing of the FAI 42 and pseudo-driver 40 drivers at the IP layer is done on an IP address specific to each network driver according to the following mechanism:

(1) arrival of the UDP packet on the IP_CAS port,

(2) recovery of the scrambled IP datagram 23, (3) passage of the original descrambled IP datagram to the pseudo-driver,

(4) recovery of data on the Destination port by the client 4.

This mechanism allows the recovery of the original datagram 23 without modification, making the descrambling function completely independent of the client. final. It only uses the IP stack in UDP / TCP mode when receiving data.

2 -Use of RAW loopback mode As illustrated in Figure 6, the data is received on the FAI interface 42 and fed back via the IP stack 44 from the client machine to the descrambler 35 awaiting UDP data on the port specific IP_CAS. The descrambler 35 recovers the data from the UDP datagram via the IP stack 44 extracts the header 24 <discriminator - access_control_header> and descrambles the original IP datagram 23. The descrambler 35 supplies this IP datagram 23 to the end client awaiting data on the original destination port in UDP or in TCP.

The IP datagram 23 is re-transmitted in the FAI / IP stack 42 via the IP stack 44 passing to the destination IP address the loopback IP address of the machine (127.0.0.0). This re-transmission takes place in RAW mode because the re-transmitted data constitute a complete IP frame which must not be modified. The loopback mechanism of the IP 44 stack therefore feeds the data without re-transmitting it. The descrambler 35 is on standby on its particular port and normally recovers the data in the clear after decapsulating the IP datagram by the IP / TCP / UDP stack.

This solution can be implemented on an operating system allowing the use of RAW mode of the IP 44 stack in loopback on the transmitter side and is done according to the following mechanism:

(1) arrival of the UDP packet on the IP_CAS port, (2) recovery of the scrambled IP datagram,

(3) passage of the original IP datagram descrambles (with the destination IP address replaced by 127.0.0.0) to the pseudo-driver in RAW and loopback mode,

(4) recovery of data on the Destination port by the end customer 4.

On the client side, this mechanism uses only the IP stack 44 in UDP / TCP mode when receiving data to pass them to the descrambler 35 as when transmitting data to re-transmit them to the final application.

FIG. 7 schematically represents a system for scrambling data in a point-to-point environment according to the invention. This system includes a terminal of a user 4, a service provider β, an ECM generator 12, a database 16, a server for presenting the offer 64, an editor for access conditions 66, a RTSP 72 audiovisual control gateway, an internet service provider 74.

The following steps describe a user's access to a VOD service using a memory card. The principle can be extended to other types of Point-to-Point services. Access begins with a subscriber authentication phase. This phase takes place just after the subscriber has connected to the Internet service provider 74.

During this session, the terminal of the user 4 goes up, its IP address, dynamically assigned by the access provider 74 at the time of the connection to the network, and the AU (unique address) of his card.

Phase 1: Presentation of the offer.

The user makes an HTTP request on a server presenting the offer 64. The user's terminal

4 receives a page presenting the offer of services in terms of acquisition of rights and in terms of presentation of content.

The presentation of the page is optional and can be managed directly by the operator. The page appears while at the request of the subscriber, when reloading rights for example.

Phase 2: Program selection

Phase 2 presupposes that the user has selected a particular service (eg choice of a film in a VoD service).

Two actions are taking place in parallel:

- The first to the browser. : phase 2; - The second to the scrambling system: phase 2 '.

In this second phase, the presentation server returns to the terminal in the HTTP response the complete URL of the film (ex: http: // served. Film-name.ram);

Phase 3: launch of the film player execution program

The user's browser activates this program (in the present example, RealPlayer) by passing the file "nom_du_film. Ram" as a parameter. The player connects to the URL http: // seryl / nom-du- film.ram. A RTSP command session (start, stop, play, rewind, forward, etc.) is then opened between the terminal 4 and the command gateway 12 redirecting the RSTP request to the most suitable flow server, the control gateway 12 and the flow server 6 are possibly combined. Phase 4: Connection to the flow server

The RTSP server then opens a TCP session with the server concerned by the delivery of the film (here served ..).

Phase 5: launch of the broadcast

The stream server 6 then transmits the film in UDP / IP datagrams to the scrambling gateway with the source address, the server address and the destination address, the address of the final client.

Phase 6: Scrambling the program

The 0 ′ gateway gateway whose Point-to-Point filters are activated automatically as soon as Point-to-Point services are detected in base 16, can then scramble generically (on @ origin) or personalized (on @ recipient) ) or depending on the URL the descending data. Phase 7: Closing a Point-to-Point session A Point-to-Point session can be closed by the scrambling gateway on time-out (no reception of packets from a given source or destination address for X seconds ). The maximum point-to-point time-out value is specified when configuring the general parameters of the equipment. APPENDIX αccess_coπtrol_heαder () j αccess_coπtroLheαder_s αrt_sequence 32 bits heσder_length 16 bits version_πumber S bits service_ID 16 bits pαyloαd_type a bits pαyloαd_5crαmbling_coπtrol 2 oirs

RUF 0 0 ûirs if (pαyloαd_scrαmbliπg_control! = 00) | scrαmbliπg_αlgorithm_tγpβ 3 bit pαyloαd_pαdding_size 8 bit pαyloαd-dsscrGmbling_wαy 3 bit cleαr_pαyloαd_CRC32 32 bit

IVoperαtor_ID_length δ bits

IVoperαtor_ID_vαlue IVoperαtorJDJeπgth * S bits

RUF 1 2 bits if (pcγlo d_desc α.τbϋr.ç_ ^, vcy == 001) |

ECM_CA_descriptor_flαg 1 bit

EM _CA_descriptor_e! Cg 1 bit

1

EC Iαg I bit

RUF 2 5 bits if (ΞCW_CA_descrîptor_f lαg = = 1) ^ Nb_ECW_CA_descriptor δ bits EC _CA_descripfor_version_πumber δ DITS for (; = 0; i <n; i ++) |

ECM_CA_descriptor ()

if (ECM_CΛ_descriptor_f! σç == 1) | δ bits

E M_CA_descriptor_γersion_πumber EMM_CA_descriptor ()

if (EC JIαg == 1) i NB ECM δ bits

TOΓ i = 0; i; i ++) | (ECM)

if (pαyloαd_descrαmbling_wαy == 010) j

RUF 3 16 bit

ED bit EDC

Claims

1. Information transmission method (20) with access control through a network (3) using an IP type protocol, characterized in that it comprises the following steps: On transmission:

- scrambling a first datagram (23);

- Define a header (24) comprising at least one piece of data identifying the access control means;

- concatenate this header (24) with the first scrambled datagram (23) to create a data block (26);

- encapsulating the data block (26) in a second IP datagram (30);

- send this second IP datagram (30) across the network; at the reception :

- extract the data block from the received datagram; - extract the header (24);

- descramble the first datagram (23) if access to this data is authorized;

- deliver the descrambled data.

2. Method according to claim 1, characterized in that the data block (26) is encapsulated in a UDP packet.

3. Method according to claim 1, characterized in that the data block (26) is encapsulated directly in an IP datagram.

4. Method according to one of claims 1 to 3, characterized in that the scrambling step comprises the following phases:

- enter at least one access condition or at least one secret key.

5. Method according to claim 1, characterized in that the data block (26) comprises: ^~

- the header (24) (Access_control_header) conveying the information necessary for the processing by a terminal (4) of the data transported;

- A sequence (Payload) representing the useful data (20) to be scrambled.

6. Method according to one of the preceding claims, characterized in that the data block

(26) respects the following syntax: CAS_data_unit () {

Access_control_header () p bytes

Payload q bytes}.

7. Method according to claim 5, characterized in that the sequence (payload) respects the following syntax: payload () {data bytes n bytes padding bytes p bytes, [p can take the value 0)

8. Method according to claim 5, characterized in that the header (24) comprises:

- a first field (header_length) representing the total length of this header (24);

- a second field (payload_scrambling_control) indicating the mode of application of the scrambling of the information (20).

9. Method according to claim 8, characterized in that the header (24) further comprises a field (EDC) representing an error detection sequence.

10. Method according to claim 8, characterized in that, if (payload_scrambling_control ≠ 00) the header (24) further comprises a field (payload_descrambling_way) indicating the mode of deactivation of the information jamming (20).

11. Method according to claim 10, characterized in that, if (payload_descrambling_way ooi: the header (24) further comprises a field

(ECM_CA_descriptor_flag) indicating the presence of at least one conditional access descriptor

(ECM_CA_descriptor) in the header (24), and a field

(ECM_flag) indicating, when its value is equal to 1, the presence of at least one ECM field () representing an access control message in the header (24).

12. Method according to claim 11, characterized in that if (ECM_CA_descriptor_flag = l), the header (24) further comprises a field (Nb_ECM_CA_descriptor) indicating the number of blocks (ECM_CA_descriptor) present in this header (24).

13. Method according to claim 8, characterized in that the header (24) further comprises a field (access_control_header_start_sequence) making it possible to identify the start of the header (24), a field (version_number) indicating the current version of the header (24), a field (service_ID) indicating the reference of the service used, a binary field (payload_type) indicating the type of data transmitted, and a field (RUFO) reserved for future use.

14. Method according to claim 10, characterized in that the header (24) further comprises a field (scrambling_algorithm_type) intended to indicate the type of algorithm used to scramble the datagram (23), and an error correcting field (CRC_32) descrambled payload.

15. Method according to claim 14, characterized in that, if the datagram (23) is scrambled by an algorithm operating in block mode, the header

(24) also includes:

- a field (payload_padding_size) specifying the number of stuffing bytes added at the end of the information (20); a field (IVOperator_ID_length) indicating, when its value is other than zero, the presence and the length of a vector field for initializing the scrambler; a field (IVOperator_ID_value) indicating, when the value of (IVOperator_ID_length) is other than zero, the value of the scrambler initialization vector, and a field (RUF1) reserved for future use.

16. Method according to claim 11, characterized in that, the header (24) further comprises a field (EMM_CA_descriptor_flag) indicating, when its value is equal to 1, the presence of at least one conditional access descriptor ΞCM_CA_descriptor ) in the header of the crou Iié datagram (23), a field (RUF2) reserved for future use.

17. The method of claim 12, characterized in that the header (24) further comprises a field

(ECM_CA_descriptor_version_number) indicating the next version of the block (ECM_CA_descriptor).

18. Method according to claim 16, characterized in that, if (EMM_CA_descriptor_flag = 1), the header

(24) further includes a field (EMM CA_descriptor_version_number) indicating the next version of the block (EMM_CA_descriptor).

19. The method of claim 11, characterized in that, if (ECM_flag = 1), the header (24) comprises in addition to a field (NB_ECM) indicating the number of ECM in the header (24) of the scrambled datagram.

20. Method according to claim 10, characterized in that, if (payload_descrambling_way = 010), the header

(24) has a field (RUF3) reserved for future use.

21. Method according to claim 11, characterized in that the access control message comprises:

- a pointer (ECM_index) intended to differentiate several ECMs to select a particular ECM for descrambling;

- a table (ECM_table) containing the ECM data and the phase change instructions.

22. Method according to claim 21, characterized in that the table (ECM_table) comprises:

- an identification field (table_id); - a field indicating the length of an ECM, (ECM_length).

23. Method according to claim 17, characterized in that the conditional access descriptor (ECM_CA_descriptor) comprises:

- a field (descriptor_tag) indicating the start of an ECM conditional access descriptor;

- a field (ECM_CA_descriptor_length) indicating the length; - a field (CA_system_ID) representing an identifier of the access control system used;

- a pointer (ECM_ιndex).

24. Method according to claim 14, characterized in that the identifier of the type of encryption algorithm comprises:

- an identifier (CI_tag); - a field (Cl-length) indicating the length of the identifier (CI_tag);

- a field (CI_value) indicating the value of the identifier (Cl-tag).

25. Method according to one of the preceding claims, characterized in that the service operator is identified by a field comprising:

- an identifier (SOID_tag) of the block used to describe the area of the service operator used in the smart card;

- a field (SOID_length) indicating the length of said zone;

- a field (SOID_value) indicating the value of the identifier (S0ID_tag).

26. The method of claim 2, characterized in that a source UDP port is allocated dynamically when the UDP link is opened.

27. The method of claim 2, characterized in that the allocation of the UDP port number of destination is achieved dynamically by a signaling protocol between the scrambler and the descrambler.

28. Method according to claim 2, characterized in that the destination UDP port number is a value dedicated by a certification authority.

29. Method according to claims 27 and 28, characterized in that the reception of datagrams

IF / UDP by the end customer includes the following steps:

- receive the second IP datagram (30),

- receive the UDP packet on the static or dynamic UDP port previously opened,

- recover and descramble the data block (26),

- extract the header (24),

- send the first IP datagram (23) descrambles to a pseudo-driver, - extract the data from the first datagram (23);

- send the extracted packet to the destination application.

30. Method according to claim 28, characterized in that the reception of UDP datagrams by the end client comprises the following steps:

- receive the second IP datagram (30);

- receive the UDP packet on the static or dynamic port opened previously; - recovering and descrambling the data block (26); - extract the header (24);

- re-transmit the first IP datagram (26) on the loopback address of the stack;

- extract the data from the first datagram (23), to send them to the recipient application.

31. Method according to one of claims 1 to 30, characterized in that the IP services transmitted are audiovisual streams over IP.

32. Method according to one of claims 1 to 30, characterized in that the transmitted IP services are data transmitted by satellite via the IP network.

33. Transmitter of scrambled data through an IP type network capable of implementing the method according to one of claims 1 to 32.

34. Transmitter according to claim 33, characterized in that it comprises means for associating with the IP datagrams (23) a header (24) comprising at least one datum identifying the access control means and an indication of the method d 'scrambling used.

35. Transmitter according to claim 34, characterized in that it further comprises means for defining the services to be scrambled by a label to which corresponds a source IP address or a destination IP address; - Means for entering at least one access condition or at least one secret key.

36. Transmitter according to claim 35, characterized in that it comprises a server (6) of IP data flow, a gateway (8) comprising an IP scrambler, an ECM generator (12), an EMM generator (14) and a database (16).

37. Receiver capable of receiving scrambled data according to claims 1 to 32 ..

38. Receiver according to claim 37, characterized in that it comprises means for extracting the header (24) from a scrambled data block (26) and means for activating at least one access condition or at least a secret key.

39. Scrambling and access control system in an IP type network, characterized in that it comprises a transmitter according to claim 33 and a receiver according to claim 37.

40. Device for scrambling and controlling access to IP services comprising a transmitter according to claim 36, characterized in that it also comprises a man-machine interface intended to define the services to be scrambled and to enter at least an access condition or a secret key.

41. Device according to claim 40, characterized in that the access control means comprise a memory card for transporting the secret key.