A method of obfuscated performance of a predetermined function, wherein for the predetermined function there is a corresponding plurality of first functions so that, for a set of inputs for the function, a corresponding set of outputs may be generated by (a) representing the set of inputs as a corresponding set of values, wherein each value comprises at least part of each input of a corresponding plurality of the inputs, (b) generating a set of one or more results from the set of values, where each result is generated by applying a corresponding first function to a corresponding set of one or more values in the set of values, and (c) forming each output as either a part of a corresponding one of the results or as a combination of at least part of each result of a corresponding plurality of the results; wherein the method comprises: obtaining, for each value in the set of values, one or more corresponding transformed versions of said value, wherein a transformed version of said value is the result of applying a bijection, that corresponds to said transformed version, to said value; and generating a set of transformed results corresponding to the set of results, wherein each transformed result corresponds to a respective result and is generated by applying a second function, that corresponds to the first function that corresponds to the respective result, to a transformed version of the one or more values of the respective set of one or more values for the corresponding first function.