It is inter alia disclosed to apply a function on a string in accordance with a rule of a set of rules, the string comprising first and second representatives, wherein the function ensures that the string comprises at least one of a predetermined representative at an end of the string after the function has been applied; and to determine a representation of the string, wherein said representation comprises at least one encoded representative, each of said at least one encoded representative being associated with at least one representative of the string, wherein said representation does not comprise an encoded representative being associated with at least one of the at least one predetermined representative at the end of the string.