1. A computer-implemented digital steganography method comprising: providing a processor with a plurality of target data elements each comprising a sequence of digital bits; providing the processor with a plurality of source data elements each comprising a sequence of digital bits; and using the processor to generate, according to a predefined extraction method, a mapping of each of the target data elements with a corresponding source data element, wherein the mapping comprises, for each target data element, a corresponding indice indicating the position of a next occurrence of that target data element within the plurality of source data elements relative to a reference location within the plurality of source data elements.