An assembler for generating a complex signature of an input multimedia data element comprises a first interface for receiving a plurality of signatures respective of a plurality of minimum size multimedia data elements, wherein each of the plurality of the minimum size multimedia data elements is a minimal partition of the input multimedia data element; an assembly unit for combining the plurality of signatures respective of the plurality of minimum size multimedia data elements to generate the complex signature; and a second interface for storing at least the complex signature in a storage unit connected thereto.