Abstract: A method is provided for encrypting a code of a computer program using an encryption key selected from among at least two encryption keys. Such a method includes: obtaining a descriptive grammar of the language of the code to be encrypted; encoding the code by using the descriptive grammar delivering a character string within which at least one start instruction of the code is encoded as a representation in the character string; encryption of the character string by using the encryption key belonging to the set of encryption keys, delivering an encrypted string. A method of decryption includes the inverse steps and also makes use of the descriptive grammar of the code.

Abstract: An antitheft protection device that includes an electronic antitheft element. The device also includes an element for deactivating the electronic antitheft element; an energy supply at least indirectly powering said element for deactivating the electronic antitheft element; and an element to receive a command to deactivate the electronic antitheft element.

Abstract: A method is provided for encrypting a code of a computer program using an encryption key selected from among at least two encryption keys. Such a method includes: obtaining a descriptive grammar of the language of the code to be encrypted; encoding the code by using the descriptive grammar delivering a character string within which at least one start instruction of the code is encoded as a representation in the character string; encryption of the character string by using the encryption key belonging to the set of encryption keys, delivering an encrypted string. A method of decryption includes the inverse steps and also makes use of the descriptive grammar of the code.

Abstract: An antitheft protection device that includes an electronic antitheft element. The device also includes an element for deactivating the electronic antitheft element; an energy supply at least indirectly powering said element for deactivating the electronic antitheft element; and an element to receive a command to deactivate the electronic antitheft element.

Abstract: The invention concerns a method for deactivating a payment module attachable to a communications terminal, comprising: a phase for deactivating comprising at least one step for erasing the main memory of said payment module with the exception of a non-volatile memory zone in which an encryption key k is stored, said encryption key k being available only when said main memory is empty; a phase for verifying comprising: a step for verifying that said main memory is empty, delivering a positive or negative result of verification; if said result of verification is positive: a step for computing a response to a challenge preliminarily received by said payment module from an entity distinct from said payment module, said computation being implemented by means of said encryption key k; a step for transmitting said response to said entity.

Abstract: The invention concerns a method for deactivating a payment module attachable to a communications terminal, comprising: a phase for deactivating comprising at least one step for erasing the main memory of said payment module with the exception of a non-volatile memory zone in which an encryption key k is stored, said encryption key k being available only when said main memory is empty; a phase for verifying comprising: a step for verifying that said main memory is empty, delivering a positive or negative result of verification; if said result of verification is positive: a step for computing a response to a challenge preliminarily received by said payment module from an entity distinct from said payment module, said computation being implemented by means of said encryption key k; a step for transmitting said response to said entity.

Abstract: A method and apparatus for obtaining an encryption key for an item of data transmitted from a client to a server. The method includes: determining a number R of registers available within the client for carrying out a plurality of calculations of encryption keys; determining a maximum number N of iterations necessary for obtaining at least one encryption key at the server; obtaining a structure of data representative of a key calculation state effected within the R available registers; calculating the at least one encryption key as a function: —of the number of available registers R, by performing at most N calls to a pseudo-random function F and —of the data structure; so that the at least one encryption key can be obtained from a combination of at most T=CR+NN?1 encryption keys based on a secret previously shared between the server and client.

Abstract: A cryptographic method is provided of a type with public key over a non-supersingular elliptic curve E, determined by the simplified Weirstrass equation y2=x3+a·x2+b over a finite field GF(3n), with n being an integer greater than or equal to 1. The method includes associating an element t of said finite field with a point P? of the elliptic field. The step of associating includes: obtaining a pre-determined quadratic non-residue ? on GF(3n); obtaining a pre-determined point P=(zP, yP) belonging to a conic C defined by the following equation: a·?·z2?y2+b =0; obtaining a point Q=(zQ, yQ), distinct from the point P belonging to the conic C and a straight line D defined by the following equation: y=t·z+yP?t·zP; obtaining the element ? of GF(3n) verifying the following linear equation over GF(3): ??·?=(?2·zQ)/a; and associating, with the element t of the finite field, the point P? of the elliptic curve, for which the coordinates are defined by the pair (?·zQ/?, yQ).

Abstract: A method and apparatus for obtaining an encryption key for an item of data transmitted from a client to a server. The method includes: determining a number R of registers available within the client for carrying out a plurality of calculations of encryption keys; determining a maximum number N of iterations necessary for obtaining at least one encryption key at the server; obtaining a structure of data representative of a key calculation state effected within the R available registers; calculating the at least one encryption key as a function: —of the number of available registers R, by performing at most N calls to a pseudo-random function F and —of the data structure; so that the at least one encryption key can be obtained from a combination of at most T=CR+NN?1 encryption keys based on a secret previously shared between the server and client.

Abstract: A method and apparatus are provided for reducing the energy consumption of an electronic terminal. The method implements a step of modifying the timeout-before-standby duration for said terminal after an action performed by and/or on said terminal at a current instant, depending on the membership of the current instant in a given temporal category, from among at least two predefined temporal categories.

Abstract: A cryptographic method is provided of a type with public key over a non-supersingular elliptic curve E, determined by the simplified Weirstrass equation y2=x3+a.x2+b over a finite field GF(3n), with n being an integer greater than or equal to 1. The method includes associating an element t of said finite field with a point P? of the elliptic field. The step of associating includes: obtaining a pre-determined quadratic non-residue ? on GF(3n); obtaining a pre-determined point P=(zP, yP) belonging to a conic C defined by the following equation: a.?.z2?y2+b=0; obtaining a point Q=(zQ, yQ), distinct from the point P belonging to the conic C and a straight line D defined by the following equation: y=t.z+yP?t.zP; obtaining the element ? of GF(3n) verifying the following linear equation over GF(3): ?3??.?=(?2.zQ)/a; and associating, with the element t of the finite field, the point P? of the elliptic curve, for which the coordinates are defined by the pair (?.zQ/?, yQ).

Abstract: A method and apparatus are provided for validating a transaction on a transactional terminal, the transaction being associated with a user. The method includes a step of decoding a validation code preliminarily generated and displayed by the transactional terminal, entered by the user in a validation message, and transmitted by a mobile device of the user to an entity of a telecommunications network to which the mobile device and said transactional terminal are connected.

Abstract: The invention relates, mainly to a cryptographic process using an elliptic curve represented by means of an equation containing first and second parameters (a, b), a bilinear matching, and calculations in a finite group of integers constructed around at least one first reduction rule reducing each integer to its remainder in a whole division by a first prime number (p) that constitutes a third parameter, the elements of the finite group being in bijection with points selected on the elliptic curve, and the number of which is linked to a fourth parameter (q), where this process uses public and private keys, each of which is represented by a given point of the elliptic curve or by a multiplication factor between two points of this curve. According to the invention, the first reduction rule is the only reduction rule implemented, and the elliptic curve is obtained through a step-by-step construction process, directly allocating to the finite group q*q q-order points in the elliptic curve.

Abstract: A method and apparatus are provided for validating a transaction on a transactional terminal, the transaction being associated with a user. The method includes a step of decoding a validation code preliminarily generated and displayed by the transactional terminal, entered by the user in a validation message, and transmitted by a mobile device of the user to an entity of a telecommunications network to which the mobile device and said transactional terminal are connected.

Abstract: A method and apparatus are provided for reducing the energy consumption of an electronic terminal. The method implements a step of modifying the timeout-before-standby duration for said terminal after an action performed by and/or on said terminal at a current instant, depending on the membership of the current instant in a given temporal category, from among at least two predefined temporal categories.

Abstract: The invention relates to a method of masking a plain datum b having n bits. The inventive method is characterised in that a masked datum m is produced using the following masking function: (I), wherein p is a prime number, bi is the bit at position i of plain datum b, and qi is the prime number at position i in a set of prime numbers (q1, . . . , qn). The invention also relates to a method of masking a biometric print, consisting in: determining a set of s real minutiae which are characteristic of the print; mixing and arranging the real minutiae with t false minutiae; and forming a mixed biometric datum b having n=s+t bits, such that, for any i: bi=1 if position i corresponds to a real minutia, and bi=0 if position i corresponds to a false minutia. The invention can be used to secure a security document such as a bank cheque.

Abstract: The invention relates to a method for secure data transmission in connections between two functional modules of an electronic unit. A first module of a message of k bits in a word code of n bits is injection coded with a constant Hamming weight of w. The word of code is transmitted to a second module. An error signal is generated when the Hamming weight of the word of code of n bits, received by the second module, is different from w. In the absence of error, the code word is decoded, where k, w and n are whole numbers. The invention further relates to a corresponding electronic circuit.

Abstract: The invention relates to a method for the secure deposition of data, according to which a depositor encrypts the data with a transfer key and encrypts the transfer key with a key of a third party, then deposits the encrypted data and the encrypted transfer key on a storage support. The invention also relates to a method for recovering data, during which an addressee of the data recovers the content of the storage support, authenticates him/herself to the third party, and transmits the encrypted transfer key thereto. After having authenticated the addressee, the third party returns the decrypted transfer key. The addressee can then recover the data. The invention further relates to devices for implementing the foregoing methods.

Abstract: The invention relates, mainly to a cryptographic process using an elliptic curve represented by means of an equation containing first and second parameters (a, b), a bilinear matching, and calculations in a finite group of integers constructed around at least one first reduction rule reducing each integer to its remainder in a whole division by a first prime number (p) that constitutes a third parameter, the elements of the finite group being in bijection with points selected on the elliptic curve, and the number of which is linked to a fourth parameter (q), where this process uses public and private keys, each of which is represented by a given point of the elliptic curve or by a multiplication factor between two points of this curve. According to the invention, the first reduction rule is the only reduction rule implemented, and the elliptic curve is obtained through a step-by-step construction process, directly allocating to the finite group q*q q-order points in the elliptic curve.

Abstract: The invention relates to a method of masking a plain datum b having n bits. The inventive method is characterised in that a masked datum m is produced using the following masking function: (I), wherein p is a prime number, bi is the bit at position i of plain datum b, and qi is the prime number at position i in a set of prime numbers (q1, . . . , qn) The invention also relates to a method of masking a biometric print, consisting in: determining a set of s real minutiae which are characteristic of the print; mixing and arranging the real minutiae with t false minutiae; and forming a mixed biometric datum b having n=s+1 bits, such that, for any i: bi=1 if position i corresponds to a real minutia, and bi=0 if position i corresponds to a false minutia. The invention can be used to secure a security document such as a bank cheque.