A speech coding apparatus includes driving excitation coding units, a comparator and a selecting unit. More specifically, this invention relates to several novel lubricating oil additives and compositions which contain a tungsten compound and an antioxidant, namely aminic antioxidants such as a secondary diarylamine or an alkylated phenothiazine. The processing unit may be configured to compute a result of a function, the function having as input the private value, to blind the result of the function to generate the encrypted blinded result, and to compute the result by unblinding the blinded result.