Secure method of processing data

Abstract

The invention relates to a secure method of processing data in which method is implemented the evaluation of a function that may be written as a linear combination of sub-functions with two binary inputs, in which a client and a server each possess a binary code, comprising n indexed bits, the method comprising the evaluation of the function with the binary codes of the client and of the server as inputs, without one of the client or the server obtaining information about the code of the other, the method being characterized in that it comprises the following steps: —the server randomly generates n indexed values and calculates the linear combination of these values with the same linear combination as that applied to the sub-functions to obtain the function, —the client implements, for each bit of his binary code, a technique of unconscious transfer to obtain from the server an intermediate data item comprising the randomly generated value of same index as the bit of the code of the client, increased by the value of the corresponding sub-function evaluated at the bit of same index of the code of the server and at said bit of his binary code, and —the client performs a linear combination of the intermediate data for all the bits of his binary code, with the same linear combination as that applied to the sub-functions to obtain the function, in such a way as to obtain a final result comprising the linear combination of the randomly generated values, increased by the evaluation of the function at the two binary codes.