A method of communication between a transmitter and a receiver, and a system comprising a transmitter and a corresponding receiver.

Abstract

The method of communication between a transmitter (Tx) and a receiver (Rx) comprises at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial (PolBr) and an initialization value (InitVal). The method includes a secret negotiation (NEG) phase between the transmitter and the receiver to specifically determine the scrambling polynomial (PolBr) and the initialization value (InitVal) for said at least one transmission. Figure for the abstract: Fig 2

Description

Title of the invention: Method of communication between a transmitter and a receiver and system comprising a transmitter and a corresponding receiver

[0001] Embodiments and implementations relate to communications between a transmitter and a receiver, including "chip-to-chip" communications, i.e., integrated circuits, using data scrambling.

[0002] Scrambling (also called scrambling, and usually "scrambling" in English) is widely used in communications to randomize (i.e. add a random or pseudo-random component) the communicated data before transmission.

[0003] Scrambling is part of line coding which is the last operation on the data before it is sent over the communication channel by the transmitter.

[0004] Scrambling is typically an exclusive-or operation "xor" between the clear data and a set of pseudo-random data, typically obtained with a linear feedback shift register "LFSR" (for "Linear Feedback Shift Register" in English). The data thus scrambled is transmitted on the channel, and the clear data can be recovered by the inverse operation, that is to say the same xor operation with the same set of pseudo-random data.

[0005] The pseudo-random data set generated by an LFSR is typically characterized by the feedback polynomial of the LFSR, also called the scrambling polynomial, and by a register initialization value.

[0006] To recover clear data, the scrambling polynomial and the initialization value must be known by the receiver before transmitting the data, which exposes conventional systems to two problems: "sniffing attacks" and "killer packet attacks".

[0007] Briefly, sniffing attacks correspond to the case where confidentiality is required in the scrambling of data, while a third party can relatively easily have knowledge of the scrambling polynomial and the initialization value, and thus recover the data in clear on the channel.

[0008] Briefly, killer packet attacks involve designing raw data packets such that once aligned with the output of the LFSR, sequences of consecutive 0s or 1s are produced and are likely to cause continuous errors at the receiver and cause the system to malfunction.

[0009] Conventionally, to guard against errors due to killer packet attacks, a new attempt to send the data is made by changing the polynomial and / or initialization, when the recipient detects an error. However, this conventional mechanism has the disadvantage of being time-consuming and does not provide protection against a new design of killer packets adapted to the new polynomial and / or initialization conditions.

[0010] Encryption of communication data is a complex solution that requires complex cryptographic algorithms that consume time and energy.

[0011] Thus there is a need to provide protection on communication channels, for example of the "chip-to-chip" type, in particular against sniffing and killer packet attacks, and advantageously in a way that is economical in terms of resources, implementation time, and energy.

[0012] Modes of implementation and realization of the aspects defined below make it possible to secure the secrecy of the scrambling polynomial and the initialization value, so that the confidentiality obtained by scrambling the data communicated on the channel is resistant against attacks based on obtaining the polynomial and the initialization, that is to say in particular attacks of the sniffing and killer packet type.

[0013] According to one aspect, there is provided a method of communication between a transmitter and a receiver comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial and an initialization value, the method comprising a secret negotiation phase between the transmitter and the receiver to specifically determine the scrambling polynomial and the initialization value for said at least one transmission.

[0014] Thus, unlike conventional techniques where the scrambling polynomial and the initialization value are predetermined for the entire communication, in this aspect a scrambling polynomial and the initialization value are specifically and secretly determined for each subset of (at least one) transmission(s) of said communication.

[0015] According to one embodiment, the secret negotiation phase comprises an exchange of encrypted information between the transmitter and the receiver, the encrypted information making it possible to specifically determine the scrambling polynomial and the initialization value by the transmitter and by the receiver.

[0016] The encryption of the negotiation phase, potentially with complex cryptographic solutions, does not suffer or only negligibly suffers from the problem of time and energy consumption, due to the fact that the quantity of information exchanged in the negotiation phase is very small, in particular negligible compared to the quantity of data communicated.

[0017] According to one embodiment, the scrambling polynomial is determined by a selection from a finite set of scrambling polynomials available to the transmitter and the receiver, the selection being made as a function of conditions contained in said encrypted information.

[0018] The conditions of the selection can be chosen jointly for the transmitter and the receiver, for example arbitrary conditions of parity or of intervals of values ​​of a digital data item, or of a portion of the digital data item, contained in said encrypted information.

[0019] According to one embodiment, the initialization value is contained directly or indirectly in said encrypted information.

[0020] For example, the initialization value can be directly communicated in a digital data item or in a portion of the digital data item, contained in said encrypted information; or indirectly communicated, for example derived by a calculation method chosen jointly for the transmitter and the receiver from a digital data item or a portion of the digital data item, contained in said encrypted information.

[0021] According to one embodiment, the secret negotiation phase comprises an exchange of Diffie-Hellmann keys, for example possibly based on elliptic curves, so as to develop a shared secret making it possible to determine the scrambling polynomial and the initialization value.

[0022] For example, the shared secret is part of said encrypted information, exchanged between the transmitter and the receiver by the key exchange mechanism, making it possible to specifically determine the scrambling polynomial and the initialization value by the transmitter and by the receiver.

[0023] According to one embodiment, the secret negotiation phase comprises an encrypted communication of the Rijndael type, also called “advanced encryption standard”, containing the determination of the scrambling polynomial and the initialization value.

[0024] For example, encrypted communication of the Rijndael type is part of said encrypted information making it possible to specifically determine the scrambling polynomial and the initialization value by the transmitter and by the receiver.

[0025] According to another aspect, there is provided a system comprising a transmitter and a receiver configured to implement a communication comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial and an initialization value, and a secret negotiation phase between the transmitter and the receiver to specifically determine the scrambling polynomial and the initialization value for said at least one transmission.

[0026] According to one embodiment, the transmitter and the receiver are configured, in the secret negotiation phase, to exchange encrypted information making it possible to specifically determine the scrambling polynomial and the initialization value by the transmitter and by the receiver.

[0027] According to one embodiment, the transmitter and the receiver are configured to have available a finite set of scrambling polynomials, and to determine the scrambling polynomial by selecting it from said set as a function of conditions contained in said encrypted information.

[0028] According to one embodiment, the transmitter and the receiver are configured to exchange said encrypted information directly or indirectly containing the initialization value.

[0029] According to one embodiment, the transmitter and the receiver are configured, in the secret negotiation phase, to carry out a Diffie-Hellmann key exchange, for example possibly based on elliptic curves, so as to develop a shared secret making it possible to determine the scrambling polynomial and the initialization value.

[0030] According to one embodiment, the transmitter and the receiver are configured, in the secret negotiation phase, to carry out an encrypted communication of the Rijndael type containing the determination of the scrambling polynomial and the initialization value.

[0031] According to another aspect, there is provided a transmitter device configured to implement a communication, with a receiver, comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial and an initialization value, and a secret negotiation phase with the receiver to specifically determine the scrambling polynomial and the initialization value for said at least one transmission.

[0032] According to another aspect, there is provided a receiver device configured to implement a communication, with a transmitter, comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial and an initialization value, and a secret negotiation phase with the transmitter to specifically determine the scrambling polynomial and the initialization value for said at least one transmission.

[0033] The transmitter device and the receiver device as defined independently above, may be capable of belonging to a system as defined above, that is to say furthermore comprise all the elements characterizing respectively the transmitter and the receiver of a system as defined above.

[0034] Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments and implementations, which are in no way limiting, and the appended drawings, in which the figures:

[0035] [Fig.l] ;

[0036] [Fig.2] ; and

[0037] [Fig.3] illustrate embodiments and implementations of the invention.

[0038] [Fig.l] illustrates an example system 100 comprising a transmitter Tx and a receiver Rx configured to implement communication on a CNL communication channel.

[0039] The transmitter Tx and the receiver Rx are for example integrated circuit devices, otherwise called “chips”. The CNL channel is for example a fast link, having a flow rate of several gigabits per second, and for example on two differential lines Dp, Dn.

[0040] An output stage of the transmitter Tx receives “raw” data DatClr or clear (i.e. unscrambled), in parallel with a rate of, for example, several megabits per second, and coming from the intelligence of the transmitter device TX, for example usually a processor or an automaton of the state machine type.

[0041] An online encoder LnCdr is configured to transform the raw data DatClr into the encoding used in the communication protocol of the CNL channel, and is further configured to introduce scrambling into the values ​​of the raw data DatClr, thereby communicating scrambled and encoded data DatBr.

[0042] The LnCdr line coding is essentially the last operation before the DatBr data is serialized by a Srlzr "serializer", and sent on the CNL channel typically via a differential amplifier (usually "driver" in English).

[0043] The differential driver is for example clocked by a signal at a frequency adapted to the CNL channel (several gigabits / sec) typically generated from a reference clock RefClk in a phase-locked loop PLL.

[0044] Scrambling is typically an exclusive-or operation "xor" between the clear data DatClr and a set of pseudo-random data, typically obtained with a linear feedback shift register "LFSR" (for "Linear Feedback Shift Register" in English).

[0045] The pseudo-random data set generated by an LFSR is characterized by the feedback polynomial of the LFSR register, also called the scrambling polynomial, and by an initialization value of the LFSR register.

[0046] The thus scrambled data DatBr are transmitted on the CNL channel, and the clear data can be recovered by the xor operation with the same set of pseudo-random data by the receiver Rx.

[0047] The receiver Rx comprises in this respect a differential receiver receiving the data transferred on the CNL channel in series, from which a clock signal and a data signal are extracted by a CDR recovery circuit (usually “clock and data recovery" in English). The encrypted and encoded data series is reorganized for parallel communication DatBr, by a "deserializer" circuit DeSrlzr.

[0048] An online decoder LnDeCdr is configured to read the data DatBr following the encoding of the CNL channel and to recover the raw data, in clear, DatClr.

[0049] The recovery of the clear data DatClr by the online decoder LnDeCdr involves the inverse operation of the scrambling operation, i.e. the same xor operation with the same set of pseudo-random data LFSR.

[0050] Scrambling the data transferred on the CNL channel makes it possible to randomize the content of the DatBr transmission in order to benefit in particular from: - a greater number of transitions in the stream of transferred data, to help with clock and data recovery in CDR reception; - a balancing of the quantity of 0 and 1, to reduce the drift of the reference level on the CNL channel (usually “baseline wander” in English); - a reduction in repeated patterns to limit electromagnetic interference; - confidentiality of the transferred content.

[0051] To guard against a breach of confidentiality based on techniques for obtaining the scrambling polynomial and the initialization value, the communication between the transmitter Tx and the receiver Rx includes a procedure for securing and keeping secret the characteristics of the scrambling (i.e. the scrambling polynomial and the initialization value).

[0052] Thus in this respect, the communication comprises a secret negotiation phase NEG (figures 2 and 3) between the transmitter Tx and the receiver Rx to determine the scrambling polynomial PolBr (figures 2 and 3) and the initialization value InitVal (figures 2 and 3) used to scramble and recover the data. The secret negotiation phase can be done specifically for each transmission on the CNL channel, or each time N successive transmissions are made on the CNL channel.

[0053] A transmission may correspond for example to a communication session, comprising for example in particular a procedure for establishing the connection on the CNL channel, the actual transfer of the data, and a procedure for verifying and ending the transmission; typically according to the communication protocol used on the channel.

[0054] The secret negotiation phase can be done for example before the transfer phase of each transmission, or before the first transfer phase of the first of the N successive transmissions, or for example during the connection establishment procedures of each session.

[0055] The secret negotiation phase NEG can be controlled and executed by a software implementation in the transmitter Tx and receiver Rx devices, in order to provide instructions to the LnCdr online encoder belonging to the hardware implementation (“physical layer” in English) of the transmitter Tx and the receiver Rx.

[0056] We now refer to figures 2 and 3 which illustrate communication methods 200, 300 in particular according to two examples of implementation of the secret negotiation phase NEG.

[0057] In the two examples 200, 300, it is considered in particular that the secret negotiation phase NEG comprises an exchange of encrypted information between the transmitter Tx and the receiver Rx, the encrypted information making it possible to specifically determine the scrambling polynomial PolBr and the initialization value InitVal by the transmitter and by the receiver.

[0058] [Fig.2] illustrates a first example 200 of the communication method between the transmitter Tx and the receiver Rx of the system 100 described above in relation to [Fig.l].

[0059] The communication method 200 thus comprises at least one transmission of scrambled data DatBr with a pseudo-random sequence generated by a scrambling polynomial PolBr and an initialization value InitVal; as well as a secret negotiation phase NEG between the transmitter Tx and the receiver Rx to specifically determine the scrambling polynomial PolBr and the initialization value InitVal for each transmission or each group of transmissions.

[0060] The secret negotiation phase NEG of the first example 200 comprises an ECDH Diffie-Hellmann key exchange, possibly based on elliptic curves, so as to develop a shared secret SCRT. The shared secret SCRT is a numerical value.

[0061] The shared secret SCRT, obtained identically by the transmitter Rx and by the receiver Tx, is used to determine the scrambling polynomial PolBr and the initialization value InitVal, specifically for this transmission.

[0062] Indeed, summarily and in a conventional manner and known per se, the Diffie-Hellmann key exchange makes it possible, from a transfer of a public key from the transmitter TxPK to the receiver Rx and a transfer of a public key from the receiver RxPK to the transmitter Tx, to construct the same shared secret SCRT by the transmitter Rx and by the receiver Tx, without ever communicating on the channel all the parameters necessary for the construction of the secret (in particular a combination of the public key of the transmitter TxPK received by the receiver Rx, with a private key of the receiver Rx; and a combination of the public key RxPK of the receiver Rx received by the transmitter Tx, with a private key of the transmitter Tx).

[0063] From the shared secret SCRT, thus developed identically by the transmitter Tx and the receiver Rx during the secret negotiation phase NEG, the scrambling polynomial PolBr and the initialization value InitVal specifically established for this are determined. transmission.

[0064] For example, the scrambling polynomial PolBr is selected from a finite set of scrambling polynomials available to the transmitter Tx and the receiver Rx. The selection is for example conditioned by numerical criteria arbitrarily established on the shared secret SCRT.

[0065] The interference polynomials belonging to said finite set available to the transmitter Tx and the receiver Rx are for example “hard coded”, that is to say in a hardware and static implementation of a circuit.

[0066] That being said, many polynomials can be provided in the “hard coding”, and the shared secret SCRT makes it possible to choose one by applying conditions previously designed in this regard, such as for example and arbitrarily: - For a set of 2 scrambling polynomials, one or the other can be selected according to the parity of the numerical value of the shared secret, i.e. according to the value 0 or 1 of the last least significant bit of the shared secret. - For a set of 3 (or other) scrambling polynomials, one of the polynomials can be selected according to the respective interval of values ​​in which the first half-byte of the shared secret is located (eg scrambling polynomial no. 1 is selected if the half-byte has a value between 0x0 and 0x4; no. 2 if between 0x5 and 0x9; no. 3 if between OxA and OxF). - For a set of 2N (two to the power of N) scrambling polynomials, one can select one of them according to the value of N bits drawn at an arbitrary position in the shared secret.

[0067] The same selection method can be used if the scrambling polynomial is implemented by software, again chosen from a finite set of polynomials, pre-established and common to the transmitter Tx and the receiver Rx.

[0068] On the other hand, the initialization value InitVal can be contained directly or indirectly in the shared secret SCRT.

[0069] Indeed, one can choose an initialization value InitVal on N bits by directly selecting N bits in the shared secret, for example the last N low-order bits or the first N high-order bits of the shared secret.

[0070] The initialization value InitVal can also be obtained indirectly on N bits by techniques of deriving the data read in a selection of N bits of the shared secret SCRT.

[0071] It will be noted that in this case 200, the shared secret SCRT can be considered as the encrypted information exchanged between the transmitter Tx and the receiver Rx, by the public key exchange mechanism TxPK, RxPK, the encrypted information SCRT making it possible to specifically determine the scrambling polynomial PolBr and the initialization value InitVal by the transmitter Tx and by the receiver Rx.

[0072] Finally, when the scrambling polynomial PolBr and the initialization value InitVal are determined by the transmitter Tx, the transmitter Tx can send a ready state signal TxRdy to the receiver Rx; and respectively under the same conditions, the receiver Rx can send a ready state signal RxRdy to the transmitter Tx.

[0073] When both ready status signals are received from both sides, then the scrambled data transmission(s) DatBr can be made on the CNL channel.

[0074] [Fig. 3] illustrates a second example 300 of the method of communication between the transmitter Tx and the receiver Rx of the system 100 described above in relation to [Fig. 1].

[0075] The communication method 300 also comprises said at least one transmission of scrambled data DatBr; as well as a secret negotiation phase NEG.

[0076] The secret negotiation phase NEG of the second example 300 comprises an AES encrypted communication, containing the determination of the scrambling polynomial PolBr and the initialization value InitVal.

[0077] The encryption of the AES communication is advantageously of the Rijndael type (a term commonly used from a contraction of the names of its two designers Joan Daemen and Vincent Rijmen), that is to say of the “advanced encryption standard” type.

[0078] Initially, the scrambling polynomial PolBr is previously selected by the transmitter Tx, again for example from a finite set of scrambling polynomials available to the transmitter Tx and the receiver Rx, potentially “hard-coded” within the transmitter device Tx and the receiver device Rx.

[0079] Thus, the scrambling polynomial PolBr is for example chosen by means of a random selection in said finite set.

[0080] The same method can be used if the scrambling polynomial is implemented by software, again chosen from a finite set of polynomials, common to the transmitter Tx and the receiver Rx.

[0081] Similarly, the initialization value InitVal is obtained beforehand by means of a random generation.

[0082] A random (or pseudo-random) data generator may be provided in the transmitter circuit, whether or not dedicated to these selection mechanisms.

[0083] When the determination of the scrambling polynomial PolBr and the initialization value InitVal are thus obtained by the transmitter Tx, this information is encrypted Encrypt by the Rijndael algorithm and communicated Encryptd_P+I to the receiver Rx.

[0084] The receiver Rx is configured to decrypt Decrypt the encrypted information Encryptd_P+I thus received, so as to recover said determinations of the scrambling polynomial PolBr and of the initialization value InitVal previously carried out randomly by the transmitter Tx.

[0085] The receiver Rx is provided in this regard with a decryption key corresponding to the AES encryption carried out by the transmitter Tx.

[0086] Thus, the encryption and decryption keys will be predetermined between the transmitter Tx and the receiver Rx, for example: - Being determined during design and recorded in the Tx transmitter and Rx receiver. This applies in particular when the Tx transmitter and Rx receiver chips are in the same product (such as for example a Tx processor and an Rx display in the same product). - Being determined with the Diffie-Hellmann method described previously, said keys can be derived from the shared secret. This applies in particular when the transmitter Tx and the receiver Rx “do not know each other” (such as for example a computer and a display, the two parties do not share a design phase and do not hold a common key).

[0087] On the other hand, the initialization value InitVal can be contained directly or indirectly in the encrypted information.

[0088] Indeed, one can directly transmit the initialization value InitVal in the encrypted information Encryptd_P+I, and one can also indirectly deduce the initialization value InitVal by techniques for deriving the content of the encrypted information Encryptd_P+I (although there is little interest in combining a derivation technique in addition to the advanced encryption standard, given the security of the latter).

[0089] It will be noted that in this case 300, the encrypted information Encryptd_P+I exchanged between the transmitter Tx and the receiver Rx, allows the receiver Rx to specifically determine the scrambling polynomial PolBr and the initialization value InitVal, previously determined by the transmitter Tx.

[0090] Finally, when the scrambling polynomial PolBr and the initialization value InitVal are determined by the receiver Rx, the receiver Rx can send a ready state signal RxRdy to the transmitter Tx; considering that sending the encrypted information Encryptd_P+I implicitly communicates a ready state of the transmitter Tx.

[0091] When the transmitter Tx and the receiver Rx are in the ready state, then the scrambled data transmission(s) DatBr can be made on the CNL channel.

[0092] In summary, examples of the realization and implementation of a secret negotiation technique NEG of the scrambling polynomial PolBr and the initialization value InivtVal between a transmitting device Tx and a receiving device Rx, without transmitting these values ​​in clear on the CNL channel.

[0093] Accordingly, the use of scrambling in encoding data according to these exemplary embodiments and implementations is not vulnerable to sniffing and killer packet attacks.

[0094] Furthermore, the invention is not limited to these embodiments and implementations, but embraces all variants thereof, and could be provided in all applications where scrambling is used, in particular chip-to-chip communications, but also in memory controllers saving scrambled data in the memories, and without strictly restricting the transmitter and receiver functions, a transmitter of one communication being able to be the receiver of another and vice versa.

Claims

Claims

1. A method of communication between a transmitter (Tx) and a receiver (Rx) comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial (PolBr) and an initialization value (InitVal), the method comprising a secret negotiation phase (NEG) between the transmitter and the receiver to specifically determine the scrambling polynomial (PolBr) and the initialization value (InitVal) for said at least one transmission.

2. Method according to claim 1, in which the secret negotiation phase (NEG) comprises an exchange of encrypted information between the transmitter and the receiver, the encrypted information making it possible to specifically determine the scrambling polynomial (PolBr) and the initialization value (InitVal) by the transmitter and by the receiver.

3. Method according to claim 2, in which the scrambling polynomial (PolBr) is determined by a selection from a finite set of scrambling polynomials available to the transmitter (Tx) and the receiver (Rx), the selection being made as a function of conditions contained in said encrypted information.

4. Method according to one of claims 2 or 3, in which the initialization value (InitVal) is contained directly or indirectly in said encrypted information.

5. Method according to one of claims 1 to 4, in which the secret negotiation phase (NEG) comprises a Diffie-Hellmann key exchange (ECDH) so as to develop a shared secret (SCRT) making it possible to determine the scrambling polynomial (PolBr) and the initialization value (InitVal).

6. Method according to one of claims 1 to 4, in which the secret negotiation phase (NEG) comprises an encrypted communication of the Rijndael type (AES) containing the determination of the scrambling polynomial (PolBr) and the initialization value (InitVal).

7. System comprising a transmitter (Tx) and a receiver (Rx) configured to implement a communication comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial (PolBr) and an initialization value (InitVal), and a secret negotiation phase (NEG) between the transmitter and the receiver to specifically determine the scrambling polynomial (PolBr) and the initialization value (InitVal) for said at least one transmission.

8. System according to claim 7, in which the transmitter (Tx) and the receiver (Rx) are configured, in the secret negotiation phase (NEG), to exchange encrypted information allowing the scrambling polynomial (PolBr) and the initialization value (InitVal) to be specifically determined by the transmitter and by the receiver.

9. System according to claim 8, in which the transmitter (Tx) and the receiver (Rx) are configured to have available a finite set of scrambling polynomials, and to determine the scrambling polynomial (PolBr) by selecting it from said set according to conditions contained in said encrypted information.

10. System according to one of claims 8 or 9, in which the transmitter (Tx) and the receiver (Rx) are configured to exchange said encrypted information containing directly or indirectly the initialization value (InitVal).

11. System according to one of claims 7 to 10, in which the transmitter (Tx) and the receiver (Rx) are configured, in the secret negotiation phase (NEG), to carry out a Diffie-Hellmann key exchange (ECDH) so as to develop a shared secret (SCRT) making it possible to determine the scrambling polynomial (PolBr) and the initialization value (InitVal).

12. System on chip according to one of claims 7 to 10, in which the transmitter (Tx) and the receiver (Rx) are configured, in the secret negotiation phase (NEG), to carry out an encrypted communication of the Rijndael type (AES) containing the determination of the scrambling polynomial (PolBr) and the initialization value (InitVal).

13. Transmitter device (Tx) configured to implement a communication, with a receiver (Rx), comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial (PolBr) and an initialization value (InitVal), and a secret negotiation phase (NEG) with the receiver (Rx) to specifically determine the scrambling polynomial (PolBr) and the initialization value (InitVal) for said at least one transmission.

14. Receiver device (Rx) configured to implement a communication, with a transmitter (Tx), comprising at least one transmission of scrambled data with a pseudo-random sequence generated by a scrambling polynomial (PolBr) and an initialization value (InitVal), and a secret negotiation phase (NEG) with the transmitter (Tx) to de- specifically terminate the scrambling polynomial (PolBr) and the initialization value (InitVal) for said at least one transmission.

15. Device according to one of claims 13 or 14, capable of belonging to a system according to one of claims 8 to 12.

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