WO2012001273A1

WO2012001273A1 - Method for the secure allocation, to a private network node, of an ipv6 address

Info

Publication number: WO2012001273A1
Application number: PCT/FR2011/051442
Authority: WO
Inventors: Jean-Michel Combes; Daniel Migault
Original assignee: France Telecom
Priority date: 2010-06-29
Filing date: 2011-06-23
Publication date: 2012-01-05
Also published as: FR2961994A1

Abstract

The invention relates to a method for the secure allocation of a network label (PFX) in a private network, the network including at least one router (RT) and at least one network node (N), the method including a step (16) of the router sending a label announcement message (RA) to the network node, said message including: a digital certificate for a public key (K_pub), the owner of which is the router; signed information including at least one network label generated by the router, the information being signed using a private key (K_priv) specific to the router and associated with the certified public key.

Description

Method for securely allocating an IPv6 address to a node of a private network

The invention relates to a technique for securely allocating IPv6 addresses in a private network, and more specifically a technique for securely allocating network prefixes.

IPv6 is a new version of the network protocol of the Internet. One of the features of IPv6 is to offer 128-bit addressing, instead of the 32-bit IP version 4 protocol. IPv6 addresses have a specific structure. Any IPv6 address includes first and second 64-bit portions. The first part, called the network prefix, is used for routing in the network. The second part corresponds to an interface identifier.

IPv6 provides an auto-configuration procedure that allows a node in a network, public or private, to generate its own address, which avoids a manual address entry procedure at the node level, or a procedure configuration via a server type "DHCP" (Dynamic Host Configuration Protocol) adapted to automatically assign an address to a node with a suitable initial setting. Such procedures, for an individual who supervises a subnetwork, for example a private network such as a home network, can be tedious or complicated.

Thus, with the auto-configuration procedure, a router adapted to ensure the routing of packets in a network sends regularly, or on demand, on a network link on which it is located announcements marked "RA" for "Router Advertisement" set by a prefix corresponding to the network prefix associated with the router. Once the router prefix obtained by the node, it can generate its own IPv6 address by concatenating the prefix announced by the router to an interface identifier of its own, and which includes for example a hash of his own address MAC.

Securing this self-configuration mechanism in a public network is provided to prevent a malicious router from performing denial of service attacks on nodes of the link. During such an attack, the malicious router may for example send in a RA announcement message a valid prefix, associated with a legitimate router, specifying that the validity period of this prefix is equal to 0. In d ' other words, this message indicates that the announced network prefix is no longer valid. The node is unable to use its IP address. The malicious router may also send an erroneous prefix, which causes the node to generate an erroneous address. The mechanism for securing self-configuration in a public network and being standardized to "IETF"("Internet Engineering Task Force") is based on the use of a mechanism called "SEND"("SecureNeighbor") Discovery "), described in RFC 3971. The security mechanism is based on the use of X.509 certificates and is based on a" Resource Public Key Infrastructure "(" RPKI ") type infrastructure. The RPKI conforms to the IPv6 address management infrastructure, in this case "IANA"("Internet Assigned Number Authority") which is the organization in charge of space management Internet IP addressing and other shared numbering resources required in IP networks.

With this RPKI, a pair of private / public keys and an X.509v3 certificate are assigned to a router by a Certification Authority recognized by ΙΑΝΑ, in Europe it is "RIPE" (for "European IP Networks"). The certificate certifies the public key associated with the private key. A router prefix which is then distributed in an advertisement message RA is signed by the router by means of its private key. Thus, a node that receives an RA announcement message verifies that the router's IPv6 address is valid. To this end :

it verifies the signature received by means of the public key associated with the router and present in the certificate;

then, it checks that the router has the right to announce the prefix it announces by checking the certificate.

The certificate is used to certify that the certificate holder, in this case the router that advertises a prefix is a router, and that it is authorized to advertise this prefix.

This mechanism is intended to certify a router public key in a public network to secure the announcement of a prefix in the public network. On the other hand, it is unsuitable for announcing a prefix in a private network and therefore does not allow nodes of the private network to generate their IPv6 address. Indeed, it is known that in the case of a private network, there is dedicated a range of addresses between a first value and a second value. An administrator of the private network, for example an Internet Service Provider, then masters the addresses between these two values and allocates them for the clients of his network according to a policy that is specific to him.

Thus, two different administrators, for example two Internet Service Providers who manage two respective private networks and who administer a respective router can independently choose the same network prefix for the respective routers of their respective private network. Thus, from this same router prefix in the two private networks, it may be that a node of the first network and a node of the second network generate the same IPv6 address. This is not problematic in terms of collision since the addresses of the nodes of each of the networks are not routed in the global Internet. However, it is clear that the security mechanism as described above can not be implemented. Indeed, a Certification Authority such as IANA or RIPE, can not allocate and sign certificates to different entities, in this case the respective routers of the two networks, because there is a risk of having several identical addresses in administratively disjoint networks.

Thus, it is not possible in a private network to certify router prefixes in the same way as in public addressing, that is to say by means of a certificate allocated by a recognized certification authority. It is therefore not possible to secure addressing in a private network IPv6. Thus it becomes possible for a malicious router to perpetrate denial of service attacks on nodes in a private network.

The invention overcomes the problem mentioned above by proposing a method for securely allocating a network prefix in a private network, the network comprising at least one router and at least one network node, the method comprising a sending step by the router to the network node of a prefix advertisement message, said message comprising:

a digital certificate of a public key (K _pub ) whose owner is the router,

- Signed information comprising at least one network prefix generated by the router, the information being signed by means of a private key (K _priv ) specific to the router and associated with the certified public key.

The method of the invention thus makes it possible to secure self-configuration of nodes in a private network, which was not possible until now. Indeed, a router transmits on a link of this network a network prefix announcement message to be used, as well as information that makes it possible to verify that the router that advertises the prefix is a router, and that it is authorized to announce this prefix. This check is possible because the announcement message includes, in addition to the prefix generated by the router, all the data that make it possible to recalculate the prefix and thus to verify that the received prefix is the one expected. On the other hand, these data are certified: the public key used in the calculation of the prefix is certified by the digital certificate that is transmitted, and the information that includes at least the prefix is signed. Thus, the authenticity of the information and the public key are guaranteed and verifiable. Thus, it is not possible for a malicious router to perpetrate a denial of service attack on private network nodes by sending a prefix advertisement message that includes the valid router prefix and a parameter that specifies the duration of the attack. life of this prefix a null value. Indeed, only the valid router is able to sign the information by means of the secret key associated with the public key certified by the transmitted certificate.

According to one embodiment of the invention, the allocation method comprises:

a step of calculating a hash of a data item comprising the public key,

a step of forming the network prefix by concatenating a predefined value specific to a private network and a plurality of bits extracted from the calculated hash.

Since the first bits of the prefix of an IPv6 address in a private network are predefined, the invention makes it possible to complete a prefix to 64 bits in such a way that a node that receives this prefix in an announcement message can verify that the prefix is well advertised by a router and that the router is authorized to announce this prefix. Indeed, the verification is done on the last 56 bits of the prefix, the first 8 bits being composed of predefined values fixed for a private network.

According to one embodiment of the invention, the allocation method further comprises: a step of generation by the router of the digital certificate of the public key, and of signature of the certificate by the router by means of the private key.

In this embodiment, a certificate specific to the router is generated by the router and signed by the router. It is therefore a self-signed certificate valid inside the private network to secure self-configuration of IPv6 addresses by nodes located within the private network. Specifically, the nodes for which auto-configuration is secure, are located on the same network link as the router and can generate an IPv6 address from the prefix announced by the router.

By using self-signed certificates, it becomes possible to set up a secure and verified IPv6 addressing in a private network without the need to deploy a RPKI type infrastructure. Thus, the invention makes it possible to set up networks with private addressing in a relatively simple manner. This aspect is interesting for corporate networks, or ad-hoc networks.

In an exemplary embodiment of the invention, the allocation method also comprises a step of generation by the router of a pair of keys comprising the private key and the associated public key.

The invention also relates to a method for generating an IPv6 address by a node in a private network, the network comprising at least one router, the method comprising:

a step of receiving from the router a prefix advertisement message comprising a digital certificate of a public key and of the holder of the router, and information signed by means of a private key specific to the router and associated with the certified public key, the information comprising at least one prefix generated by the router,

a step of calculating a second prefix from the public key of the certificate,

a step of comparing the received prefix and the calculated second prefix,

a step of verifying the signature of the information by means of the public key certified by the certificate.

A node on a network link that receives the Router Prefix Announcement RA message may from this message verify that the received prefix is valid by recalculating the same prefix from the received parameters and the certificate. It can also verify that the router is authorized to issue this prefix, by verifying the signature of the information received.

Advantageously, the step of verifying the signature of the method for generating an IPv6 address is performed only if the prefix received from the router is equal to the second calculated prefix.

Indeed, the signature verification operation being expensive in terms of computing resources for the network node, the latter performs the signature verification only if the received prefix actually corresponds to the prefix calculated from the parameters and the certificate. transmitted.

Advantageously, the method for generating an IPv6 address further comprises a step of concatenating the received prefix with an interface identifier specific to the node. The network node that receives and verifies a prefix according to the method of the invention can forge its own IPv6 address from an interface identifier of its own with the guarantee that its address is authentic.

The invention also relates to a public key X.509v3 digital certificate for the router, comprising an "ExtendedKeyUsage" field adapted to indicate a usage associated with the public key, characterized in that the field comprises a value indicating that the public key is intended to be used to implement the method of securely allocating a network prefix according to the invention.

The invention also relates to a router in a private network comprising at least one network node, the router comprising:

sending means, arranged to send to the network node a prefix advertisement message comprising a digital certificate of a public key whose owner is the router, as well as signed information including at least one generated network prefix by the router, the information being signed by means of a private key specific to the router and associated with the certified public key.

In an exemplary embodiment of the invention, the router further comprises:

computing means, arranged to calculate a hash of a data item comprising the certified public key,

means for forming a prefix, arranged to form a network prefix associated with the router by concatenating a predefined value specific to a private network and a plurality of bits extracted from the calculated hash,

means for generating and signing a certificate, arranged to generate and sign the private key certificate using the private key.

The invention also relates to a node in an IPv6 private network comprising at least one router, the node comprising:

reception means, arranged to receive from the router a prefix advertisement message comprising a digital certificate of a public key and of the owner of the router, and information signed by means of a private key specific to the router and associated with the certified public key, the information comprising at least one prefix generated by the router,

calculating means, arranged to calculate a second prefix from the public key of the certificate,

comparison means, arranged to compare the announced prefix and the second prefix,

- Signature verification means, arranged to verify the signature of the signed information by means of the public key certified by the certificate.

Advantageously, the invention also relates to an IPv6 private network comprising:

at least one router according to the invention, and at least one node according to the invention.

Such a network is for example a private enterprise network, or an ad-hoc network. In the context of the invention the entities of these networks, in this case routers and network nodes according to the invention can set up their private addressing plan easily and securely.

The invention also relates to a computer program intended to be installed in a memory of a router, comprising instructions for implementing the steps of the method for securely allocating a network prefix according to the invention, when the program is executed by a processor.

The invention also relates to a computer program for installation in a memory of a network node, comprising instructions for implementing the steps of the method for generating an IPv6 address according to the invention when the program is executed. by a processor.

Many details and advantages of the invention will be better understood on reading the description of a particular embodiment with reference to the accompanying drawings given in a non-limiting manner and in which:

FIG. 1 represents the steps of the method of securely allocating an IPv6 address to a node in a private network, according to a first embodiment of the invention;

FIG. 2 represents a first exemplary embodiment of a router according to the invention;

FIG. 3 represents an exemplary embodiment of a network node according to the invention.

The steps of an exemplary embodiment of the method for securely allocating an IPv6 address to a node of a private network will now be described in relation to FIG. 1.

An N node in a private network (not shown) is adapted to generate an IPv6 compliant address according to an auto-configuration mechanism. The private network also comprises an RT router located on the same network link as the N node. It is known that according to the IPv6 protocol, a 128-bit IP address comprises in a first part of 64 bits a network prefix, and in a second part of 64 bits an interface identifier. It is also known that entities of a private network, such as the node N and the router RT, have a network prefix which starts with a predefined value of 8 bits, including a field called "Prefix" of 7 bits and a field named "L" of 1 bit. The "Prefix" field has the value "FC00:: / 7" and the "L" field is "1", in accordance with RFC 4193. These 8 bits are reserved to prefix any address in a private network. Such addresses are referred to as local addresses and are not intended to be routed in the global Internet.

In an initial step 10, the router RT generates a pair of private / public keys in accordance with an asymmetric cryptographic algorithm, for example "RSA" (named after their authors "Rivest, Shamir and Adleman"). Note this pair of keys (K _pr , K _pub ). In another embodiment, it is assigned such a pair in a secure manner by an entity adapted to generate and deliver key pairs.

In a step 11 of creating data for the generation of a prefix, the router RT concatenates the value of the public key Kpub with a set of parameters chosen by the router for the current generation of network prefix. Examples of parameters are the generation date of the prefix, a random (or "nonce"), the "MAC" address of the router RT (of "Media Access Control"), an interface identifier of the router RT . The parameters concatenated to the public key are intended to prevent the new prefix generated from being identical to the prefix previously generated when the router generates a new prefix generation from the same private / public key pair. The parameters participate in the manufacture of the network prefix. The data created in step 11 is the result of the concatenation of the public key with all the parameters.

In a hash step 12, the router RT proceeds to hash the data obtained in the previous step. It uses for example the function "SHA-1" ("Secure Hash Algorithm") which provides a 160-bit print.

In a bit extracting step 13, the router RT applies a function F to the hash obtained previously in order to obtain 56 bits. The function F can take many forms. For example, it may consist in extracting from the hashed the 56 most significant bits, or the 56 least significant bits, or the first 56 even bits, or the first 56 odd bits. The function F is of course not limited to these examples.

In a step 14 for obtaining a prefix, the router RT concatenates the first 8 bits of the reserved predefined value to designate that an IPv6 address corresponds to an address in a private network, with 56 bits obtained during the previous step. The resulting 64-bit data sets the RT router prefix in the private network. The prefix obtained at the end of this step 14 is denoted PFX. Thus, the PFX prefix obtained is the concatenation of the 7 bits of the "Prefix" field of value "FC00 :: / 7", with the bit "L" of value "1" and with the 56 bits obtained during step 13.

In a step 15 for generating and signing a certificate, the router RT generates a certificate, here in X.509 version 3 format, adapted to certify the public key K _pub of the router RT. The X.509v3 certificate is a data structure with several fields, including:

the identity of the certificate holder (subject field),

the value of the certified public key,

the generated prefix, in order to link it to the certificate holder,

- the identity of the certifying authority that signs the certificate and therefore certifies the authenticity of the public key, and

a digital signature of all the fields. In the exemplary embodiment described here, the certificate holder is the router RT designated by its IP address, and the certification authority that certifies the public key is the router RT. Thus, the certificate generated by the router RT is called self-signed certificate since it is the router RT, holder of the certificate, which certifies the authenticity of the public key by signing all the fields of the certificate by means of the private key K _priv associated with the public key K _pub which appears in the certificate.

In a sending step 16, the router RT sends on the network link a message RA announcing the prefix PFX generated in the previous steps. Specifically, the RA message includes information signed by the router RT by means of the private key K _priv , and the certificate generated and self-signed by the router RT in step 15. The information includes the prefix PFX obtained in step 14, the set of parameters chosen by the router during the step 11 of creating data for the generation of a prefix, and a lifetime indicating how long the IPv6 addresses created from the prefix PFX are valid. Lifetime is a parameter usually sent in an RA announcement message. Note that the public key certified by the certificate and all the parameters that are transmitted in the announcement message can recalculate the prefix PFX.

The prefix announcement RA message is sent by the router RT on the network link on which it is located at regular intervals. In another exemplary embodiment (not shown), the announcement message RA is sent following a solicitation of the node N.

In a reception step 17, the node N receives the announcement message RA.

In a step 18 of calculating a second prefix PFX ', the node N calculates a second prefix from the received announcement message. For this purpose, in a substep 18-1 for creating data to generate the second prefix, the node N extracts from the certificate received in the RA message the public key K _pub certified. It also extracts from the information received in the announcement message RA all the parameters which, concatenated with the public key K _pub in step 11, made it possible to obtain the data used to generate the prefix. Then, in a sub-step 18-2 for calculating a hash, the node N applies a hash function to the data obtained in the preceding sub-step 18-1. The hash function is the same function used by the router RT during step 12 of hashing, SHA-1 in the example described here. In a sub-step 18-3 of bit extraction, the node N extracts 56 bits of the hash calculated in the substep 18-2. The bits are extracted in the same way as by the router RT in step 13: by applying the same function F to the hash calculated in the substep 18-2. Then, in a sub-step 18-4 for obtaining the second prefix, the node N concatenates the 8 bits of the reserved predefined value to designate that an IPv6 address corresponds to an address in a private network with 56 bits obtained during of sub-step 18-3. At the end of substep 18-4, Node N has constructed a second 64-bit prefix PFX '. In a comparison step 19, the node N compares the PFX prefix received from the router RT in the announcement message RA during the step 17 to the second prefix PFX 'calculated by the node N during the step 18.

If the prefixes compared to step 19 are equal, then in a next signature verification step, node N verifies the signature of the information received in the announcement message RA. This verification is carried out using the public key K _pub extracted from the certificate. Signature verification is performed only if the prefixes are identical. Indeed, this check is expensive in terms of computing resources and is useless if the prefixes are not identical. In this case, it means that the PFX prefix received from the router RT has not been calculated from the certified public key extracted from the received certificate and from the set of received parameters.

If the signature check performed in step 20 is positive, then it means that the RT router that sent the RA announcement message is legitimate to advertise the PFX prefix since it has the secret key that was used to sign the information received.

In a subsequent step 21 of forming an IPv6 address, the node N generates its own IPv6 address in the private network by concatenating the PFX prefix received from the router RT with its own interface identifier IID. It obtains this interface identifier for example from a hash of its MAC address.

Steps 11 to 15 are performed by the router RT whenever the prefix thereof is to be renewed. Such a procedure is rare and is initiated by a network administrator. In an alternative embodiment of prefix renewal, step 10 is also executed.

In an alternative embodiment of the method of securely allocating an IPv6 address in a private network, no parameter is concatenated to the public key K _pub during the step 11 of creating data for the generation of data. a prefix. Thus, only the public key of the router is used for the generation of the prefix. This variant is conceivable when the router uses a new pair of private / public keys during a generation of a new prefix. Indeed, in this case, the new prefix generated is necessarily different from the previous prefix, since the public key used as a parameter of the hash function is different.

The invention is not limited to the hash function SHA-1 for the calculation of the hash by the router RT during the step 12, and by the node N during the substep 18-2. Other hash functions can be used, such as MD-5 ("Message Digest") that generates a 128-bit print, or SHA-256 that generates a 256-bit print. It is necessary, however, that the router RT and the node N use the same hash function. In the exemplary embodiment described here, an X.509 certificate is used. Some fields of an X.509 certificate have been presented above. RFC 2459 provides a detailed description of X.509 certificates and RFC 3779 has extensions used for IP addresses and appeared in version 3 of X.509. An X.509 certificate is a data structure that includes a plurality of fields. In particular, the certificate includes:

- a version number; v3 is the version adapted for the invention,

- a serial number,

- the identity of the Certificate Authority issuing the certificate, in this case the RT router, designated by its IP address,

- the name of the signature algorithm used by the Certification Authority to sign the certificate,

- a period of validity of the certificate,

- the name of the certificate holder (corresponding to the "subject" field), in this case the RT router designated by its IP address;

- information about the public key:

- algorithm to use with the public key,

- the public key itself,

- optional information, appearing according to the version of the standard and relating to the holder and / or the signatory and / or extensions, and

- the signature of the certificate by the Certification Authority, here, the router RT.

Among the optional information that appeared in version 3 of the X.509 certificates, a first field, called "KeyUsage" characterizes the use that can be made of the public key. For example it is specified that the certified public key (and therefore the associated private key) is intended to be used for signature, encryption, certificate signing. A second field, called "ExtendedKeyUsage" is adapted to indicate one or more uses of the public key certified additionally, or to replace the use specified in the previous field. Such a field can be specified according to the needs of an organization. Thus, this field is adapted to specify, in the context of the invention, that the certified public key can be used to generate a network prefix. In addition, an extension defined in RFC 3779 introduces a field that binds an IP address, such as a prefix, to a certificate holder. This field designated "addressesOrRange" is used in the invention to link the generated prefix to the router RT. An RT router according to an exemplary embodiment of the invention will now be described in relation to FIG. 2.

An RT router according to the invention provides a basic function of a router: the routing of packets. As a router, it allows nodes that are on the same network link as it to access other nodes of the same link or another link of the same network. It also allows these nodes to access one or more other networks. For packet routing to be possible, the RT router advertises a network prefix on the network link on which it is located, so that nodes located on this link generate a network address of their own which associates them, for routing, with the router RT. The router announces the prefix regularly or on solicitation of a node.

The RT network includes:

a microprocessor 201, or "CPU" (of the "Central Processing Unit") which is a processing unit;

a RAM 202 which makes it possible to perform calculations such as, for example, calculating a hash, a signature, generating a certificate, and signing it. The memory also makes it possible to load software instructions corresponding to the steps of the method for securely allocating a network prefix in a private network described above, and to have them executed by the processor 201;

a storage memory 203, for example a memory of the "ROM" type (from the English

"Read Only Memory"), adapted to store for example a self-signed certificate generated by the router and whose owner is the router RT, a private key / public key pair. Alternatively, the memory may contain a secure area adapted to securely store the secret key of the router;

network interfaces 204, adapted to allow entities such as nodes of the private network, or another router of the private network, or routers of another network to communicate with the router RT. On the other hand, they allow the router RT to access one or more networks, for example the Internet, and thus provide access to the network to the nodes of the private network that rely on it to route their packets;

means 205 for generating a private / public key pair specific to the router RT.

These means comprise for example an RSA function and means for choosing prime numbers. Once generated, the pair of keys can be stored in the storage memory 203. The means 205 implement step 10 of the secure allocation method described above;

means 206 for generating a certificate, for example an X.509v3 certificate adapted to certify the public key of the private key / public key pair generated by the means 205. These generation means 206 are arranged to complete fields of an X.509v3 certificate. For example, these means fill the fields holder and signer of the certificate with the IP address of the router. It is indeed for the router RT that the certificate is generated and it is the router RT which signs the certificate as Certification Authority. The generation means 206 also specify in an X.509v3 extension called "addressesOrRange" the network prefix generated by the router; this extension is intended to bind the network prefix to the certificate holder. These means 206 also specify in an "ExtendedKeyUsage" field a value indicating that the secure allocation method of a network prefix according to the invention is implemented. This field is intended to specify a use of the certified public key. ;

signature means 207, arranged to sign the certificate generated by the means 206 by means of the private key of the private key / public key pair. The means 206 of generation and the signature means 207 implement step 15 of the allocation method previously described;

calculation means 208, arranged to calculate a hash of a data item comprising the public key associated with the private key specific to the router. These calculation means 208 comprise a hash function, for example SHA-1. The calculation means 208 implement the concatenation step 12 and the hash step 12 of the previously described allocation method;

means 209 for forming a network prefix, arranged to concatenate a predefined value specific to a private network and a plurality of bits extracted from the hash calculated by the calculation means 208. The means 209 for forming a network prefix set implementing bit extraction step 13 and step 14 of the allocation method previously described;

means 210 for sending an announcement message, arranged to send to the network node or nodes located on the same network link as the router a prefix announcement message comprising the digital certificate associated with the public key, and signed information including at least the prefix formed by the router, the information being signed by means of the private key. The sending means 210 cooperate with the network interfaces 204 to send the announcement message on the network link. The sending means 210 implement the step 16 of sending the allocation method described above.

The network interfaces 204, the means 205 for generating a pair of keys, the means

206 of generating an X.509v3 certificate, the means 207 for signing, the means 208 for calculating the hash, the means 209 for forming a network prefix and the means 210 for sending an announcement message are preferably software modules comprising software instructions for executing the steps of the method of securely allocating a previously described network prefix, implemented by the processor of a router.

The invention therefore also relates to:

a computer program comprising instructions for implementing the method of securely allocating a network prefix as described above when this program is executed by a processor;

- a recording medium readable by a router on which is recorded the computer program described above.

The software modules can be stored in, or transmitted by, a data carrier.

This may be a hardware storage medium, for example a CD-ROM, a magnetic diskette or a hard disk, or a transmission medium such as a signal or a telecommunications network. A network node N according to an exemplary embodiment of the invention will now be described in relation to FIG. Such a node may be any computer machine such as a user terminal, or a server, used in a private network. Such a node is able to communicate with other entities, such as the router RT or another node of the private network. It is also able to communicate with entities of another network, via the Internet. The packets that it sends or receives are routed by the RT router. Node N comprises:

a microprocessor 301, or "CPU" (of the "Central Processing Unit") which is a processing unit;

a RAM 302 which makes it possible to perform calculations such as, for example, calculating hashes, checking signatures, making comparisons, concatenations. The memory also makes it possible to load software instructions corresponding to the steps of the method for generating an IPv6 address in a private network described above, and to have them executed by the processor 301;

a storage memory 303, for example a ROM memory, adapted to store, for example, the network prefix, the certificate received from a router, the public key;

network interfaces 304, adapted to allow other entities of the private network, for example the router RT (not shown) to communicate with the node N and the node N to communicate with these other entities. They also allow access to the entities of another network via the Internet, through the router RT which is responsible for routing packets to and from the N node;

receiving means 305, arranged to receive from a router located on the same network link a prefix announcement RA message comprising a digital certificate, adapted to certify a public key associated with a private key specific to this router , and signed information, the information including at least one prefix generated by the router. The receiving means 305 cooperate with the network interfaces 304. The receiving means 305 implement step 17 of the method for generating an IPv6 address, described above;

means 306 for calculating, arranged to calculate a second prefix PFX 'from the public key certified by the certificate and received by the receiving means 305. The calculation means 306 implement step 18 of calculating a second prefix of the method for generating a second prefix described above. More specifically, the calculation means 306 implement substeps 18-1 for concatenation, 18-2 for calculating a hash, 18-3 for extracting and 18-4 for obtaining a prefix;

means 307 for comparison, arranged to compare the announced prefix received in the announcement message by the reception means 305 and the second prefix calculated by the calculation means 306. The comparison means 307 implement step 19 of comparing the method for forging an IPv6 address, described above;

- Signature verification means 308, arranged to verify the signature of the signed information received in the announcement message by the receiving means 305. The verification means 308 use the public key certified by the certificate. The signature verification means 308 implements the process verification step for forging an IPv6 address, described above;

the node N also comprises concatenation means 309, arranged to concatenate a prefix generated by the router and received by the reception means 305 with an interface identifier specific to the node. The concatenation means 309 comprise means for calculating the interface identifier, obtained for example by applying a hash function to the MAC address of the node N. The concatenation means 309 implement the training step 21 an IPv6 address of the method for forging an IPv6 address, described above.

The network interfaces 304, the reception means 305, the calculation means 306, the comparison means 307, the signature verification means 308 and the concatenation means 309 for forming an IPv6 address are preferably software modules comprising instructions. software for performing the steps of the method for forging an IPv6 address previously described, implemented by the processor of a network node.

The invention therefore also relates to:

a computer program comprising instructions for implementing the method for generating an IPv6 address as described above when this program is executed by a processor;

The software modules can be stored in, or transmitted by, a data carrier. This may be a hardware storage medium, for example a CD-ROM, a magnetic diskette or a hard disk, or a transmission medium such as a signal or a telecommunications network.

The invention also relates to a private network comprising at least one router according to the invention and at least one network node according to the invention. The network node is located on the same network link as the router.

Claims

A method for securely allocating a network prefix (PFX) in a private network, the network comprising at least one router (RT) and at least one network node (N), the method comprising a step (16) of sending by the router to the network node a prefix advertisement (RA) message, said message comprising:

a digital certificate of a public key (K _pub ) whose owner is the router,

The method of claim 1, comprising:

a step (12) of calculating a hash of a data item comprising the public key,

a step (14) for forming the network prefix by concatenating a predefined value specific to a private network and a plurality of bits extracted from the calculated hash.

The method of claim 2, further comprising:

- A step (15) of generation by the router of the digital certificate of the public key, and signature of the certificate by the router by means of the private key.

4. Method according to claim 3, comprising a step (10) for generation by the router of a pair of keys comprising the private key and the associated public key.

A method for generating an IPv6 address by a node in a private network, the network comprising at least one router, the method comprising:

a step (17) of reception from the router of a prefix advertisement (RA) message comprising a digital certificate of a public key and of the holder of the router, and information signed by means of a private key specific to the router and associated with the certified public key, the information comprising at least one prefix generated by the router,

a step (18) for calculating a second prefix (PFX ') from the public key of the certificate,

a step (19) for comparing the received prefix and the calculated second prefix,

a step (20) of verifying the signature of the information by means of the public key certified by the certificate.

The method of claim 5, wherein the step of verifying the signature is performed only if the prefix received from the router is equal to the second calculated prefix.

The method of claim 5, further comprising a step (21) of concatenating the received prefix with an interface identifier specific to the node.

8. X.509v3 public key digital certificate for the router, comprising an "ExtendedKeyUsage" field adapted to indicate a usage associated with the public key, characterized in that the field includes a value indicating that the public key is intended to be used to implement the method of claim 1.

9. Router (RT) in a private network comprising at least one network node, the router comprising:

means (210) for sending, arranged to send to the network node a prefix advertisement message comprising a digital certificate of a public key whose owner is the router, as well as signed information including at least one network prefix generated by the router, the information being signed using a private key specific to the router and associated with the certified public key.

The router of claim 9 further comprising:

calculation means (208), arranged to calculate a hash of a data item comprising the certified public key,

means (209) for forming a prefix, arranged to form a network prefix associated with the router by concatenating a predefined value specific to a private network and a plurality of bits extracted from the calculated hash,

means (206, 207) for generating and signing a certificate, arranged to generate and sign the private key certificate using the private key.

11. Node (N) in an IPv6 private network comprising at least one router, the node comprising:

receiving means (305) arranged to receive from the router a prefix advertisement message comprising a digital certificate of a public key and of the owner of the router, and information signed by means of a private key of its own to the router and associated with the certified public key, the information comprising at least one prefix generated by the router,

computing means (306) arranged to calculate a second prefix from the public key of the certificate, means (307) for comparison, arranged to compare the announced prefix and the second prefix,

- Signature verification means (308) arranged to verify the signature of the signed information by means of the public key certified by the certificate.

12. IPv6 Private Network including:

at least one router according to claim 9, and

at least one node according to claim 11.

13. A computer program for installation in a memory of a router, comprising instructions for implementing the steps of the method of secure allocation of a network prefix according to one of claims 1 to 4, when the program is executed by a processor.

Data carrier on which the computer program according to claim 13 is stored.

A computer program for installation in a memory of a network node, comprising instructions for implementing the steps of the method for generating an IPv6 address according to one of claims 5 to 7 when the program is executed. by a processor.

Data carrier on which the computer program according to claim 15 is stored.