Abstract: A method is provided for generating a correspondence table suitable for use in a cryptographic processing method and comprising storing a plurality of input data and of output data in the table, each input datum being associated with at least one output datum in the table. For each input datum, at least one of the output data is obtained by applying a coding function to a first subsidiary datum and to an encrypted intermediate datum depending on the input datum. Also provided are a corresponding encryption method, a storage unit suitable for storing the correspondence table generated by the above generation method, a device for physically implementing such a correspondence table, a decryption device including such a storage unit, and a computer program product suitable for implementing the above generation method.

Abstract: A method and apparatus are provided to perform a cryptographic task on at least one numerical datum in an electronic hardware component. The method includes a step of at least partial use of an encryption function. This encryption function includes a basic encryption function obtained by the addition between an intermediate function arising from composition of a coding function with a first function, and a second function. This method can be applied to the encryption of a datum or to the decryption of a datum. Also, a method is provided for generating a public key and a device able to implement one of these methods.

Abstract: A method and system for a user to obtain a derived value Kr of m bits, in which, given two pseudo-random functions g0 and g1 from m bits to m bits, said user obtains, on the basis of an input parameter consisting of a word r of n bits, a derived value Kr=grn? . . . gr2?gr1 (S), where, for i=1, . . . , n, gri=g0 if ri=0, and gri=g1 if ri=1, and where S is a master value of m bits which is not disclosed to said user. This method comprises the following steps: a search is conducted, from among a set of words of m bits Uj, where j=1, . . . , p, recorded in a table TU and equal to Uj=gvl(j)(j)? . . . gv2(j)?gv1(j) (S), where, for i=1, . . . , l(j), the indices vi(j) are predetermined bits, for a word U? equal to U?=grl(?)? . . . gr2?gr1 (S); said derived value Kr is thereafter obtained by calculating Kr=grn? . . . grl(?)+1 (U?). Application to the encryption/decryption of pay-per-use digital contents, and to authentication.

Abstract: The invention relates to a secure communication between an electronic label (A) and a reader (B), in particular for the authentication of the label by the reader, in which: the reader (31) transmits at least one datum (Ch) to the label, the label calculates a combination comprising at least the datum from the reader (Ch)) and a secret (Si) specific to the label, and the label communicates (32) the result (C(Si, Ch)) of the combination to the reader (B) for verification purposes. The aforementioned combination (C(Si, Ch)) is preferably calculated using a current secret value (Si) delivered by a pseudo-random number generator (33). The reader (B) is also provided with a homologous pseudo-random generator.

Abstract: The invention relates to a method of generating a pseudorandom string of terms belonging to a finite body K of cardinal q?2 intended to be used in a cryptography procedure, said method comprising the iterative calculation of a system (?) of m polynomials with n variables belonging to the finite body K. According to the invention, the coefficients of these m polynomials are regenerated at each iteration. The invention also relates to pseudorandom string generator intended to implement this method.

Abstract: The invention proposes a method and a device for decrypting an encrypted message represented by a sequence C or applying an electronic signature to a sequence C, said sequence C consisting of data belonging to a finite field K=GF(q), where q>1, in which there are processed successive blocks each comprising (n·d) successive data items from the sequence C, where n and d are predetermined integers greater than 1, the processing of such a block including the following steps: applying a predetermined affine invertible transformation t?1 to said block; interpreting the resulting block as being formed of n successive elements (y1, y2, . . . , yn) of an extension E=GF(qd) of the field K; calculating an n-tuplet (x1, x2, . . .

Abstract: A method is provided for generating a correspondence table suitable for use in a cryptographic processing method and comprising storing a plurality of input data and of output data in the table, each input datum being associated with at least one output datum in the table. For each input datum, at least one of the output data is obtained by applying a coding function to a first subsidiary datum and to an encrypted intermediate datum depending on the input datum. Also provided are a corresponding encryption method, a storage unit suitable for storing the correspondence table generated by the above generation method, a device for physically implementing such a correspondence table, a decryption device including such a storage unit, and a computer program product suitable for implementing the above generation method.

Abstract: A device and a method of cryptographically hashing a message M, including the following steps: forming a sequence (M1, . . . , Mi, . . . , Mc) of data m-tuples M1=(a1,1, . . . , a1,m), . . . Mi=(ai,1, . . . , ai,m), . . . , Mc=ac,1, . . . , ac,m), where m is a strictly positive integer, from said message M; iteratively calculating successive output p-tuples V1, . . . , Vi, . . . , Vc, where p is a strictly positive integer, corresponding to said sequence (M1, . . . , Mi, . . . , Mc) of data m-tuples as a function of at least one set of multivariate polynomials defined over a finite field; and determining a hashing value of said message M as a function of the last output p-tuple Vc.

Abstract: A method and apparatus are provided to perform a cryptographic task on at least one numerical datum in an electronic hardware component. The method includes a step of at least partial use of an encryption function. This encryption function includes a basic encryption function obtained by the addition between an intermediate function arising from composition of a coding function with a first function, and a second function. This method can be applied to the encryption of a datum or to the decryption of a datum. Also, a method is provided for generating a public key and a device able to implement one of these methods.

Abstract: A method and system for a user to obtain a derived value Kr of m bits, in which, given two pseudo-random functions g0 and g1 from m bits to m bits, said user obtains, on the basis of an input parameter consisting of a word r of n bits, a derived value Kr=grn? . . . gr2?gr1 (S), where, for i=1, . . . , n, gri=g0 if ri=0, and gri=g1 if ri=1, and where S is a master value of m bits which is not disclosed to said user. This method comprises the following steps: a search is conducted, from among a set of words of m bits Uj, where j=1, . . . , p, recorded in a table TU and equal to Uj=gvl(j)(j)? . . . gv2(j)?gv1(j) (S), where, for i=1, . . . , l(j), the indices vi(j) are predetermined bits, for a word U? equal to U?=grl(?)? . . . gr2?gr1 (S); said derived value Kr is thereafter obtained by calculating Kr=grn? . . . gr1(?)+1 (U?). Application to the encryption/decryption of pay-per-use digital contents, and to authentication.

Abstract: The invention relates to a secure communication between an electronic label (A) and a reader (B), in particular for the authentication of the label by the reader, in which: the reader (31) transmits at least one datum (Ch) to the label, the label calculates a combination comprising at least the datum from the reader (Ch)) and a secret (Si) specific to the label, and the label communicates (32) the result (C(Si, Ch)) of the combination to the reader (B) for verification purposes. The aforementioned combination (C(Si, Ch)) is preferably calculated using a current secret value (Si) delivered by a pseudo-random number generator (33). The reader (B) is also provided with a homologous pseudo-random generator.

Abstract: The invention proposes a method and a device for decrypting an encrypted message represented by a sequence C or applying an electronic signature to a sequence C, said sequence C consisting of data belonging to a finite field K=GF(q), where q>1, in which there are processed successive blocks each comprising (n·d) successive data items from the sequence C, where n and d are predetermined integers greater than 1, the processing of such a block including the following steps: applying a predetermined affine invertible transformation t?1 to said block; interpreting the resulting block as being formed of n successive elements (y1,y2, . . . ,yn) of an extension E=GF(qd) of the field K; calculating an n-tuplet (x1,x2, . . .

Abstract: The invention relates to a method of generating a pseudorandom string of terms belonging to a finite body K of cardinal q?2 intended to be used in a cryptography procedure, said method comprising the iterative calculation of a system (?) of m polynomials with n variables belonging to the finite body K. According to the invention, the coefficients of these m polynomials are regenerated at each iteration. The invention also relates to pseudorandom string generator intended to implement this method.

Abstract: A device and a method of cryptographically hashing a message M, including the following steps: forming a sequence (M1, . . . , Mi, . . . , Mc) of data m-tuples M1=(a1,1, . . . , a1,m), . . . Mi=(ai,1, . . . , ai,m), . . . , Mc=ac,1, . . . , ac,m), where m is a strictly positive integer, from said message M; iteratively calculating successive output p-tuples V1, . . . , vi, . . . , Vc, where p is a strictly positive integer, corresponding to said sequence (M1, . . . , Mi, . . . , Mc) of data m-tuples as a function of at least one set of multivariate polynomials defined over a finite field; and determining a hashing value of said message M as a function of the last output p-tuple Vc.

Abstract: A method for universal calculation on the points of an elliptic curve defined by a quartic equation uses identical programmed calculating devices for operating an addition of points, a doubling of points and an addition of a neutral point. The calculating device is a central unit associated with a memory. The invention also concerns a cryptographic method using such a universal method. The invention further concerns a component for implementing the universal calculation method and/or the cryptographic method. For example, the invention is applicable to smart cards.