Abstract: The present invention relates to a method for decrypting a secret encrypted by a QC-MDPC mechanism, the decryption method being implemented by the receiver (14) and comprising the reception of a syndrome polynomial derived from the secret, the generation of random integers, the application of respective operations on the first and second sparse polynomials of the private key, the application of a third operation on the syndrome polynomial, the search for modified error polynomials such as the linear combination of modified error polynomials gives the modified syndrome polynomial, and the deduction of the shared secret by application of a respective operation on the first and second modified error polynomials, the five operations depending on the generated random integers and keeping the weight of the polynomial on which the operation is applied.

Abstract: A method and system for testing the cryptographic integrity of data m comprises at least the following elements: a module transmitting a message M, said module comprising a memory for storing the parameters used to execute the steps of the method, such as the key, the public data, a transmission medium, a receiver module also comprising storage means for storing at least the same parameters as in transmission. The system may comprise storage means for storing confidential data such as the secret keys, a processor suitable for executing the steps.

Abstract: A method of transmitting information between a plurality of radioelectric stations and an associated transmission network are disclosed. In one aspect, the method transmits information between radioelectric stations, each station including a transmitter and a receiver, the information including NbMot words of data, NbMot being an integer >1.

Abstract: A method of transmitting information between a plurality of radioelectric stations and an associated transmission network are disclosed. In one aspect, the method transmits information between radioelectric stations, each station including a transmitter and a receiver, the information including NbMot words of data, NbMot being an integer >1.

Abstract: A method and system for testing the cryptographic integrity of data m comprises at least the following elements: a module transmitting a message M, said module comprising a memory for storing the parameters used to execute the steps of the method, such as the key, the public data, a transmission medium, a receiver module also comprising storage means for storing at least the same parameters as in transmission. The system may comprise storage means for storing confidential data such as the secret keys, a processor suitable for executing the steps.

Abstract: The invention relates to a method for broadcasting data in a system using a BES (A1) stateless scheme using a binary tree T with a KEKs No 2 key structure, i.e. such that a key ki,j is associated with each difference of subsets Si,j, and a root key k0, - - - associated with the set of the tree T and a BES (A2) “stateful” scheme using the same binary tree T with a KEKs No 1 key structure, i.e. such that a key ki is associated with each subtree Si wherein the scheme (A1) is used for the current broadcast session and the keys known by the denied users are updated with a “stateful” scheme (A2) from time to time.

Abstract: A method for managing keys making it possible for a user to access one or more given services S in a communication system, in which the user is not able to be continuously connected to this service. A key K(t) is generated, which provides access to the service of day [t] for all the t<tfin by using a one-way function in the following manner (a one-way function being defined as being a function for which it is not currently possible by computing means to obtain the inverse function). A root key K(tfin) is used and the key K(tfin-1) is generated for the day [tfin-1] prior to the day tfin, by using a function f such that K(tfin?1)=f(K(tfin)). The new value of key K(tfin-1) is used in order to generate the key for the previous day K(tfin-2) and this step is reiterated over the limited time period of day [t] to day [t+d] in order to obtain the chain K(t+d?1), K(t+d?2), etc.

Abstract: Method and system are disclosed for managing erratic interruptions in a transmission system where the messages to be transmitted are composed of data packets and are expressed by means of a polynomial of degree t?1. The senders and the receivers share information making it possible to reference the data packets. In the course of the transmission of a message represented by a polynomial P, at least t points Ai are generated and P(Ai) of the polynomial P is evaluated, with t? greater than or equal to t. The evaluations P(Ai) are transmitted of the t? points to the receiver or receivers concerned, with information allowing the receivers to detect the transmission errors.

Abstract: Device for implementing modular multiplication, characterized in that it comprises at least one computation cell comprising a multiplier-adder comprising p pipelined logic-register pairs, receiving several digits to be added together and multiplied, at least two outputs corresponding to the low order and to the high order, an adder receiving the two outputs of the multiplier-adder, the number p being chosen in such a way that the maximum frequency of the multiplier-adder is greater than or equal to the maximum frequency of the adder.

Abstract: A method for managing keys making it possible for a user to access one or more given services S in a communication system, in which the user is not able to be continuously connected to this service. A key K(t) is generated, which provides access to the service of day [t] for all the t<tfin by using a one-way function in the following manner (a one-way function being defined as being a function for which it is not currently possible by computing means to obtain the inverse function). A root key K(tfin) is used and the key K(tfin?1) is generated for the day [tfin?1] prior to the day tfin, by using a function f such that K(tfin?1)=f(K(tfin)). The new value of key K(tfin?1) is used in order to generate the key for the previous day K(tfin?2) and this step is reiterated over the limited time period of day [t] to day [t+d] in order to obtain the chain K(t+d?1), K(t+d?2), etc.

Abstract: Method and system are disclosed for managing erratic interruptions in a transmission system where the messages to be transmitted are composed of data packets and are expressed by means of a polynomial of degree t?1. The senders and the receivers share information making it possible to reference the data packets. In the course of the transmission of a message represented by a polynomial P, at least t points Ai are generated and P(Ai) of the polynomial P is evaluated, with t? greater than or equal to t. The evaluations P(Ai) are transmitted of the t? points to the receiver or receivers concerned, with information allowing the receivers to detect the transmission errors.

Abstract: The invention relates to a method for broadcasting data in a system using a BES (A1) stateless scheme using a binary tree T with a KEKs No 2 key structure, i.e. such that a key ki,j is associated with each difference of subsets Si,j, and a root key ko, - - - associated with the set of the tree T and a BES (A2) “stateful” scheme using the same binary tree T with a KEKs No 1 key structure, i.e. such that a key ki is associated with each subtree Si wherein the scheme (A1) is used for the current broadcast session and the keys known by the denied users are updated with a “stateful” scheme (A2) from time to time.

Abstract: This invention concerns an improved modular reduction device. The modular reduction device includes a multiplier using an alternative of the Montgomery multiplication process using a high numeration base r with r being equal to or greater than 4. It applies more particularly to the calculation components used for asymmetrical cryptography.

Abstract: Device for implementing modular multiplication, characterized in that it comprises at least one computation cell comprising a multiplier-adder comprising p pipelined logic-register pairs, receiving several digits to be added together and multiplied, at least two outputs corresponding to the low order and to the high order, an adder receiving the two outputs of the multiplier-adder, the number p being chosen in such a way that the maximum frequency of the multiplier-adder is greater than or equal to the maximum frequency of the adder.