Abstract: The device comprises an EEPROM memory. A data written in this memory is considered to be valid if two "neutral" locations are situated contiguously with the data to be validated.The "neutral" locations are produced by a prior erasure which is necessary for the EEPROM memory in order to write a data.

Abstract: This method of processing data protected by a coding is particularly suitable to be used in microcircuit cards utilizing the method of processing data of the DES type. In the DES method, a step SP of transformation of compression S is included, which is followed by an irregular permutation P. According to the method, the transformation of compression S is effected in such a manner that the data to be stored are subjected beforehand to a permutation P, while a masking system is calculated specifically to permit the execution of the said step SP by recuperating only the desired bits, the latter then being automatically present at the predetermined storage locations.

Abstract: This method of processing data protected by encryption is particularly suitable for smart cards utilizing the DES system. The method enables the execution of the irregular permutation of the key on the basis of a correspondence table, which operation is most costly as regards processing time and code length in the cited system. The method involves the decomposition of the initial permutation into a plurality of elementary permutations so that the majority thereof is performed on at least two bits, the bits of the various octets of the key being marked, a masking system being applied in order to extract the appropriate bits for their permutation in the positions predetermined by the correspondence table.

Abstract: A method of rotating a word constituted by binary elements b.sub.0 to b.sub.p-1 arranged from a position P(i) to a position P(i+p-1) in a global format containing p+n binary elements arranged according to the positions P(1) to P(p+n), which global format is contained in one or more registers (K0-K7) as elementary formats is performed by a microprocessor (8) for carrying out instructions with respect to the elementary formats of clockwise rotation, counterclockwise rotation and an instruction of transfer of a binary element to a carry register (c), which instructions are stored in a read-only memory.