A method, in a processing system comprising one or more processing units and one or more storage units, for generating secure alternative representation, wherein the method comprises: providing, by the processing system, a first sequence comprising a plurality of first values; providing, by the processing system, a plurality of storage cells belonging to a plurality of groups, each of the groups having one or more storage cells; performing, by the processing system, for each of the storage cells a symbol-deriving and cell-filling procedure, comprising: deriving, by the processing system, one or more secret pointers, each of the one or more secret pointers pointing to one of the first values; forming, by the processing system, a token by putting together one or more of the first values which are pointed by the one or more secret pointers; mapping, by the processing system, the token into a symbol; and filling, by the processing system, the symbol into the corresponding one of the storage cells; composing, by the processing system, a queue for each of the groups by picking up one or more symbols filled in the one or more storage cells of a corresponding one of the groups; and generating, by the processing system, a secure alternative representation for the first sequence by concatenating the composed queue for each of the groups. providing, by the processing system, a first sequence comprising a plurality of first values; providing, by the processing system, a plurality of storage cells belonging to a plurality of groups, each of the groups having one or more storage cells; performing, by the processing system, for each of the storage cells a symbol-deriving and cell-filling procedure, comprising: deriving, by the processing system, one or more secret pointers, each of the one or more secret pointers pointing to one of the first values; forming, by the processing system, a token by putting together one or more of the first values which are pointed by the one or more secret pointers; mapping, by the processing system, the token into a symbol; and filling, by the processing system, the symbol into the corresponding one of the storage cells; composing, by the processing system, a queue for each of the groups by picking up one or more symbols filled in the one or more storage cells of a corresponding one of the groups; and generating, by the processing system, a secure alternative representation for the first sequence by concatenating the composed queue for each of the groups. deriving, by the processing system, one or more secret pointers, each of the one or more secret pointers pointing to one of the first values; forming, by the processing system, a token by putting together one or more of the first values which are pointed by the one or more secret pointers; mapping, by the processing system, the token into a symbol; and filling, by the processing system, the symbol into the corresponding one of the storage cells; composing, by the processing system, a queue for each of the groups by picking up one or more symbols filled in the one or more storage cells of a corresponding one of the groups; and generating, by the processing system, a secure alternative representation for the first sequence by concatenating the composed queue for each of the groups.