Sagem Securite

Morpho

Isabelle Sengmanivanh

Hervé Pelletier

A method of coding a secret, a numerical value, subdivided into a number N of secret elements [], a composition law () applied to the elementsgiving the value. The following are calculated: (A) a first image (T) of the secret by iterative calculation and application of the law () between the first image Tof rank i&#x2212;1 and of the product according to this law of the element () of next rank and of a random value (R) of a first set, (B) a first numerical value (S) by application of the law () to the N random values (R), (C) a second numerical value (S) by application of the law to the N&#x2212;1 random values (A) of a second set, (D) a second image T' of the secret by application of the inverse law () to the first image (T) and to the second numerical value (S) so as to generate an intermediate image (Tx) and then application of the inverse law to the intermediate image (Tx) and to the second numerical value (S). The random value (A) of corresponding rank is allocated (E) to the first N&#x2212;1 elements (d) and the value of the second image (T&#x2032;) is allocated (E) to the last element (). Application to secret or public key cryptography processes.

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Paris, France

Isabelle Sengmanivanh