The invention proposes a method comprising the evaluation of a function F obtained by applying to n sub-functions fi a first operation, the evaluation comprising: the application of a series of calculation steps in which a first unit assumes a role of a client and a second unit assumes a role of a server, and the repetition of the series of calculation steps in which the roles of client and of server are exchanged between the units, each series of steps comprising: a) randomly generating, by the server, first data, and a second datum, b) for each sub-function fi, generating by the server a set of elements formed by: a result of fi evaluated in the data of the client and of the server, masked by a first datum, by applying the first operation between the result and the first datum, and masked by the second datum, by applying between the masked result and the second datum of a second operation different from the first and distributed relatively to the latter, c) recovering by oblivious transfer, by the client, an intermediate datum corresponding to one of the elements generated by the server, d) generating, by the server, a first result portion, by: masking each first datum with the second datum, applying to all the first masked data of the first operation, and e) generating by the client, a second result portion, by applying all the intermediate data of the first operation.