Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/32—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials
  • H04L9/3236—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials using cryptographic hash functions
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/185—Space-based or airborne stations; Stations for satellite systems
  • H04B7/18502—Airborne stations
  • H04B7/18506—Communications with or from aircraft, i.e. aeronautical mobile service
  • H04B7/18508—Communications with or from aircraft, i.e. aeronautical mobile service with satellite system used as relay, i.e. aeronautical mobile satellite service
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
  • H04L2209/30—Compression, e.g. Merkle-Damgard construction
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
  • H04L2209/80—Wireless

Definitions

• the invention relates to methods for transmitting and receiving data, in particular for secure exchanges between an aircraft and a base on the ground, corresponding devices and an aircraft equipped with such devices.
• the algorithms implementing these processes (generally software executed by microprocessors at the transmitter or receiver level) must be sufficiently robust (and therefore developed and tested with particularly strong constraints) and include detection and treatment of malfunctions, which makes them complex and expensive to develop. It is therefore necessary in practice to choose for the processing of data to exchange software with a high level of certification.
• the invention proposes a data transmission method, characterized by the steps of: - determining a data authentication word;
• processing data to obtain processed data comprising a compression step
• the authentication word is thus relative to the data before processing, in particular before compression, which makes it possible in particular to verify, during the verification of the authentication implemented at the reception, the absence of error in the processing carried out. at the show as at the reception.
• the determination step includes for example the application of a hash function to the data; the mathematical properties of hash functions are thus used, whereby any modification in the data implies a change in the result, that is to say the authentication word (or fingerprint).
• the application of the hash function can furthermore use a cryptographic key, which makes it possible to improve the security of the system.
• the aforementioned processing further includes, for example, an encryption step (possibly applied to the data and the authentication word) and / or a step of converting words from 8 bits into 6-bit words, or from a stream binary (in English "bitstream") in transmittable characters.
• the transmission channel is a data exchange channel between an aircraft and a ground base.
• the invention also proposes a method for receiving data, characterized by the following steps:
• processing of the received data comprising a decompression step
• the authentication verification being applied to the processed data (in particular, uncompressed), it will in particular ensure the accuracy of the processing performed.
• the verification step comprises for example in practice the following steps: - calculation of a fingerprint of at least part of the processed data;
• the step of calculating the imprint may include a step of applying a hash function to said data portion, in a manner corresponding to what was evoked on transmission and with the same advantages.
• the application of the hash function can then also use a cryptographic key.
• the received print is in general the result of an application, on transmission, of the hash function to data to be transmitted.
• the processing may further comprise a decryption step and / or a step of deconversion of 6-bit words into 8-bit words, or characters received in a bit stream.
• the invention also proposes a data transmission device characterized by means for determining a data authentication word, data processing means for obtaining processed data, the processing means comprising compression means, and means for transmitting data processed on a transmission channel.
• the invention proposes a device for receiving data characterized by means for receiving data on a transmission channel, means for processing the data received, the processing means comprising decompression means, and means for receiving data. verification of an authentication of the processed data.
• These devices may have optional characteristics corresponding to the steps and characteristics envisaged above for the transmission and reception processes. These devices can equip for example an aircraft.
• FIG. 1 represents the general context of the invention
• FIG. 2 represents the main steps of a data transmission method according to the invention
• FIG. 3 represents the main steps of a method of receiving the data transmitted by the method of FIG. 2.
• FIG. 1 represents the general context in which the invention is implemented.
• a ground base B communicates with an aircraft A by means of a link that allows the exchange of data in digital form (that is to say according to the English term "data HnK 1 ) and which notably involves a ground link -air C A.
• the connection between the ground base B and the aircraft A may also involve other devices and links.
• the ground base B communicates with a relay R (also located on the ground T) by means of a terrestrial communication network C ⁇ ; the relay R transmits the information to and from the aircraft A via a satellite S.
• relay R is relatively common because the information exchanged between the ground base B and the aircraft A are conventionally routed by the relay R and the satellite S under the responsibility of a supplier of service. As a variant, provision could be made for the information to be exchanged directly between the aircraft A and the ground base B.
• FIG. 2 represents an example of a data transmission method which represents, for example, a message M in digital form.
• the device transmitting the message M can be a communication device of the ground base B or a communication device of the aircraft A. It is considered that example that the message M is represented in binary form by a sequence of bytes (or 8-bit word). Other types of coding than 8-bit coding are naturally conceivable for the message M.
• the transmitting device then proceeds (for example within a microprocessor controlled by software implementing the steps of FIG. 2) to the determination of an authentication word (or imprint) E of the message
• a hash function of the SHA2 type is used.
• the footprint E resulting from the application of the hash function to the message M, has a predetermined length, for example 256 bits.
• the mathematical properties of the hash functions are such that any modification of the message M would result in a modification of the fingerprint obtained by applying the hash function.
• the comparison of the E-pattern of the message M obtained on transmission, on the print calculated at the reception thus makes it possible to verify that the message M has not been altered, and consequently to verify its integrity.
• the use of the cryptographic key K present on both the sending and the receiving side, will allow, as described below, the receiver to verify that the imprint E has been obtained by a system holding the cryptographic key K , which makes it possible to check the origin of the message M, and thus to protect itself from an attack on the communication link.
• the footprint E attached to the message M as indicated in the following, therefore allows the authentication thereof.
• the transmission device then proceeds to encrypt the set formed by the message M and the print E during a step E22, which forms an encrypted message D.
• an encryption algorithm of the AES type is used. .
• the footprint E is therefore integrated in the entire message to be transmitted before the encryption step E22.
• this footprint could however be integrated for transmission at a later stage.
• the encrypted message D is then compressed into a compressed message F by means of a compression algorithm, for example of the ZLIB type (step E24).
• the transmitting device finally proceeds to the conversion of the compressed message F into a message G to be transmitted coded on 6 bits during a step E26.
• This conversion step makes it possible to transmit, with transmission devices working on 6-bit words, the compressed message F initially coded on 8 bits.
• FIG. 3 represents the main steps of the method of reception of the transmitted message, which thus aims at restoring the initial message M from the raw data received (referenced G 'in the following) and which therefore comprises steps substantially complementary to those of the receiving process and in reverse order.
• a message (or set of data) G 'in the form of 6-bit words is first received.
• the received message G ' is identical to the message sent G.
• the receiving device i.e., in general, a microprocessor of the receiving device acting under the control of software
• step E34 of decompression of the message F 'in order to obtain an encrypted message D' equal to the encrypted message D in the event of normal operation.
• the decompression algorithm used is the inverse of the compression algorithm of step E24 mentioned above.
• the receiving device then proceeds to decrypt the encrypted message D 'during a step E36, which makes it possible to reconstruct a message M' and a print E ', identical respectively to the message M transmitted and to the print E determined in FIG. step E20 under normal operating circumstances.
• each of the following causes causes an output of normal operation and could therefore introduce a difference between the message M and the print E at the time of transmission, and the message M 'and the print E'. obtained in step E36: an error in the processing of these elements by the transmitting device, in particular during the algorithms implemented in the steps E22 to E26 described above;
• the authentication of the received message M ' is checked by means of the received fingerprint (or authentication word received) E '.
• the receiving device proceeds during a step E38 to the calculation of the fingerprint E "of the received message M 'by applying it to the latter.
• the message M 1 is equal to the message M; the footprint calculated at the reception E "is therefore equal to the footprint calculated at the emission E and consequently at the received footprint E ', which has, by hypothesis, been processed and transmitted without error.
• step E40 it is verified for authentication in step E40 that the received fingerprint E 1 is equal to the fingerprint calculated at the reception E ": it is considered in case of equality (step E42) that the message received and processed M 1 is in accordance with the message M emitted by the transmitting device.
• the message received is not taken into account, and it is possible to request its retransmission by the transmitting device, and it is also noted that, thanks to the use of the known cryptographic key, only the devices authorized to be exchanged messages, it is impossible for an attacker to provide the receiving device with a fingerprint E 'which would be the result of the application of the hash function to a modified message and which would be the only one likely to authenticate the message m modified by the receiving device.
• Authentication thus makes it possible to ensure the origin and the integrity of the message, and thereby to verify the accuracy of the processing carried out after the authentication on transmission and before the authentication on reception.
• These treatments will therefore not require a maximum level of safety; in practice, the algorithms that implement these processes may have a certification level lower than that required for the entire process, the certification being then provided by the authentication algorithm.
• the example which has just been described represents only one possible embodiment of the invention.
• the example described uses a mechanism authentication using a symmetric key K, but one could alternatively consider using other authentication mechanisms, for example private key systems and public key.
• other types of function than the hash function can be used to provide the authentication mechanism.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Computer Security & Cryptography (AREA)
• Physics & Mathematics (AREA)
• Astronomy & Astrophysics (AREA)
• Aviation & Aerospace Engineering (AREA)
• General Physics & Mathematics (AREA)
• Mobile Radio Communication Systems (AREA)
• Storage Device Security (AREA)
• Facsimile Transmission Control (AREA)
• Small-Scale Networks (AREA)

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• 2006
  • 2006-03-29 FR FR0651086A patent/FR2899408B1/fr not_active Expired - Fee Related
• 2007
  • 2007-03-27 CN CNA2007800106216A patent/CN101573911A/zh active Pending
  • 2007-03-27 EP EP07731206A patent/EP1999886A1/fr not_active Withdrawn
  • 2007-03-27 CA CA002643989A patent/CA2643989A1/en not_active Abandoned
  • 2007-03-27 BR BRPI0707036-5A patent/BRPI0707036A2/pt not_active IP Right Cessation
  • 2007-03-27 US US12/294,311 patent/US8572390B2/en active Active
  • 2007-03-27 WO PCT/FR2007/000524 patent/WO2007110509A1/fr active Application Filing
  • 2007-03-27 RU RU2008142767/08A patent/RU2481716C2/ru not_active IP Right Cessation
  • 2007-03-27 JP JP2009502144A patent/JP2009531904A/ja active Pending

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