Abstract: The invention relates to a method for authenticating a product from an analyte of the clarity of translucent blocks contained in a two-dimensional code, a method for authenticating a two-dimensional code and devices for carrying out said methods. The two-dimensional code affixed to a product is authenticated by analysing the level of clarity of translucent areas contained in the two-dimensional code and comparing the result of said analysis with a reference in a pre-established database. The two-dimensional code is authenticated by selectively marking certain dark areas of the two-dimensional code according to the character chain encoded during an encoding step and comparing the position of the marked dark areas with the position defined by the character chain during a decoding step. The invention also relates to a novel application of said two-dimensional code.

Abstract: The invention concerns a multiple private key and secondary key cryptography method, including segmentation into blocks having a specific number of characters, and, for each block, a first step of encrypting each block with a first part of the multiple private key, determining an intermediate key specific to the block from the multiple private key and the secondary key, processing each block with at least one algorithm dependent on the intermediate key, said processing providing a processed block, and a second step of encrypting the processed block, and, for the set of blocks, forming a cryptogram including the processed blocks and characters representing the secondary key.

Abstract: A method for making secure message transmission includes a step of transmitting the message and its signature by the transmitter (1) as well as an identification information of the transmitter (CRYPTIDENT) and a supplementary information derived from the message (IDEM), and the receiver (2) likewise determines an information derived from the content of the received message and compares it to the transmitted corresponding information (IDEM) to validate the message in case of conformity.

Abstract: The invention concerns a method for producing an encrypted information from character strings and numeric values of specific size and representing items to be protected for identifying forgery of administrative documents or documents delivered by public authorities comprising the following steps which consist in: condensing said strings into several numbers of n figures smaller in size than the number representing the size of the strings to constitute a first set of m intermediate results of n figures; transforming said m intermediate results, with an algorithm randomly drawn among several, into a second result of n figures expressed in base 10 produced by a matrix converting characters of an alphanumeric base into digital characters of a decimal base stored by a computing system; converting said second result expressed in base 10 into another so-called encrypted result with the same number of n figures, expressed in a mathematical base randomly selected by the computing system among a specific selection of a