Secure data processing method and use in biometry

Abstract

The invention relates to a processing method, including the calculation of one function between a datum to be compared and a reference datum. The function can be written in the form of a sum of: a term that depends on the datum to be compared, a term that depends on the reference datum, and a polynomial, such that all the monomials of the polynomial include at least one coordinate of each datum. The method includes an initialization step including: generating masking data; scrambling reference data by means of a server unit on the basis of said masking data; and calculating, by means of a client unit, the term of the function that depends on the datum to be compared. The method also includes steps for executing the calculation of the function between the datum to be compared and the reference datum, indexed by an index c, during which: the client unit sends the coordinates of the datum to be compared to a secure component, which returns said datum, in a masked form, to said component; the client unit retrieves, from the server unit, the reference datum, indexed by the index c and scrambled by the masking data; and on the basis of the data obtained from the secure component and the server unit, the client unit calculates the sum of the term of the function that depends solely on the reference datum and the polynomial term and adds, to said sum, the term that depends on the datum to be compared, such as to obtain the result of the function.