Oberthur Technologies

U.S. Philips Corporation

De La Rue Cartes Et Systemes Sas

Robert Naciri

Arnaud Boscher

Christophe Giraud

Jean P Bournas

Data processing method and related devices for determining the result of a first type of operation involving an operand in an electronic entity comprising a non-volatile storage unit, includes the following steps: converting a data, derived from at least one key portion designed to be used with the operand in the first type of operation, into a key data adapted to be used with the operand in a second type of operation; storing the key data in the non-volatile storage unit; reading in the non-volatile storage unit the key data; performing the second type of operation with the read key data and the operand.

Data processing method and related device

A data processing method, whereby an element is subjected to a first operation with a given operand. The method includes a step of updating by a second operation a first variable (B; a; S', S&#x2032;) or a second variable (A; a; S, S), depending on whether a corresponding bit of the operand=0 or 1; and a step of testing a relationship between a first value (B; a; S&#x2032;) derived from the first variable and a second value (A; a; S) derived from the second variable. A related device is also disclosed.

Method for processing data involving modular exponentiation and related device

The procedure involves key numbers 'd' and 'e' and a modulus N, so hat 'N' is the product of two factors 'p' and 'q' which are prime numbers N=p.q, and e.d=1.sub.MOD.phi.(N), where .phi.(N) is the Euler indicator function. The procedure provides enciphered message parts and for deciphering them comprises: a modulus-determining step for determining a deciphering modulus chosen from 'p' and 'q', a modular reduction step for making a first modular reduction of the number 'd' with a modulus equal to said deciphering modulus '(p-1),(q-1)' with the aim of producing a reduced number, a reduction step for making a second modular reduction of each enciphered message part with a modulus equal to said deciphering modulus with the aim of producing a reduced enciphered message part, an exponentiation step for computing a modular exponentiation of each reduced enciphered message part with a modulus equal to said deciphering modulus and with an exponent equal to said reduced number with the aim of restoring said message.

Communication system for messages enciphered according to an RSA-type

This device is designed for carrying out a division of a dividend A formed by 'm' words with a base 'b' by a divisor D. It comprises an active memory (2), a multiplication member which forms part of a calculation unit (8) provided with a first input (x.sub.i) for 'x' words of a multiplicand and with a second input (A.sub.i) for 'y' words of a multiplier. Accumulating means are provided for adding to locations of the memory (2) a multiple of a quantity db.sub.k.multidot. b.sup.j worked out by the said multiplication member, as well as testing means for providing an indication of the zero value of a separator S in the said location, and for activating the cumulation means until the testing means provide the said indication, as well as decrementation means for decrementing the value J at each indication. The remainder of the division is present in the last locations, and the quotient in the first ones.

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Chatenay Malabry, France

Robert Naciri