Abstract: 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.

Abstract: 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; a0; S?p, S?q) or a second variable (A; a1; Sp, Sq), depending on whether a corresponding bit of the operand=0 or 1; and a step of testing a relationship between a first value (B; a0; S?) derived from the first variable and a second value (A; a1; S) derived from the second variable. A related device is also disclosed.

Abstract: 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; a0; S?p, S?q) or a second variable (A; a1; Sp, Sq), depending on whether a corresponding bit of the operand=0 or 1; and a step of testing a relationship between a first value (B; a0; S?) derived from the first variable and a second value (A; a1; S) derived from the second variable. A related device is also disclosed.

Abstract: A method for cryptographic processing of a message by a secret key includes the following steps: determination of a third data item (a0) and a fifth data item (a1?eCtrl), including calculation, as a function at least of a first data item (m) obtained from the message and a second data item (d) obtained from the secret key, of the third data item (a0) and a fourth data item (a1) linked by a verification relationship, and including obtaining the fifth data item (a1?eCtrl) by combination of the fourth data item (a1) and a data item (eCtrl) representing the second data item (d); verification of the verification relationship between the third data item and a combination of the fifth data item and the second data item.

Abstract: 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.

Abstract: 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.

Abstract: 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.