Idemia Identity & Security France

Safran Identity & Security

Guillaume Dabosville

Victor Servant

Emmanuel Prouff

Houssem Maghrebi

Philippe Gislard

The present invention relates to a method for encryption or decryption of a data block from a secret key, wherein the method comprises: generating a first round key kdependent on the secret key, selecting each of a first mask (&#x2212;b) and a second mask (&#x2212;b) in a set consisting of a mask of bits all at one and a mask of all zero bits, calculating a first masked key k' from the first round key kand the first mask (&#x2212;b) as follows:&#x2295;(&#x2212;)wherein &#x2295; is an exclusive disjunction, executing a first encryption round applied to two first data dependent on the data block, by means of the first masked round key k&#x2032; so as to produce two second data, after producing the first masked key k&#x2032;, generating a second round key kdependent on the secret key, calculating a second masked key k&#x2032; from the second round key kand the second mask (&#x2212;b) as follows: k&#x2032;=k&#x2295;(&#x2212;b), calculating two third data L, Ras follows:&#x2295;(&#x2212;)&#x2295;(&#x2212;)&#x2295;(&#x2212;)&#x2295;(&#x2212;)and executing a second encryption round following the first encryption round, wherein the second encryption round is applied to the two third data L, Rby means of the second masked round key k&#x2032;.

Encryption/description method protected against side-channel attacks

The present invention relates to a method for symmetrical encryption or decryption of a data block from a secret key (K), the method comprising steps of:

Method for symmetric block encryption or decryption

The invention relates to a cryptographic processing method comprising multiplication of a point P of an elliptic curve on a Galois field by a scalar k, the multiplication comprising steps of: storing, in a first register, a zero point of the Galois field, executing a loop comprising at least one iteration comprising steps of: selecting a window of w bits in the non-signed binary representation of the scalar k, w being a predetermined integer independent of the scalar k and strictly greater than 1, calculating multiple points of P being each associated with a bit of the window and of the form &#xb1;2P, adding or not in the first register of multiple points stored, depending of the value of the bit of the window with which the multiple points are associated, wherein the loop ends once each bit of the non-signed binary representation of the scalar k has been selected, returning a value stored in the first register. If all the bits of the window selected during an iteration of the loop are zero, the iteration comprises at least one dummy execution of the addition function, and/or if all the bits of the window during an iteration of the loop are non-zero, the multiple points to be added in the first register during the step are determined from a non-adjacent form associated with the window.

Cryptographic processing method comprising multiplication of a point of an elliptic curve by a scalar

Provided is a method for optimising memory writing in a device implementing a cryptography module and a client module calling functions implemented by the cryptography module. The device includes a random access memory including a first memory zone that is secured and dedicated to the cryptography module and a second memory zone dedicated to the client module. When the client module calls a series of functions implemented by the cryptography module including a first function and at least one second function, with each second function executed following the first function or from a further second function and providing a runtime result added to a runtime result of the preceding series function, each runtime result is added to a value contained in a buffer memory allocated in the first memory. The buffer memory value is copied to the second memory zone following the execution of the last function of the series.

Growing community of inventors

Issy les Moulineaux, France

Guillaume Dabosville