1. A method for operating an electronic system to secure a multi-round cryptographic calculation procedure wherein each round is performed using a round-operation that uses a secret key and an encryption function f or a replacement thereof, the method comprising operating the electronic system to: determine a sequence of round-operations selected from a set of round-operations including round-operations performing a function p selected from the set of functions f, a masking operation followed by f, and f followed by an unmasking operation, and defined by whether each input of the round-operation has an input-type of masked or unmasked, respectively, and at least one output having an output-type of masked or unmasked depending on the input-types for the inputs, respectively, and the function p; wherein the sequence of round-operations is selected such that for two sequential rounds i and i+1, each output from round i serves as an input to round i+1 and the output-type for each output from round i matches the input-type for the corresponding input to round i+1; and execute the determined sequence of rounds.