A CODING METHOD, PARTICULARLY A NUMERIC CODING METHOD

摘要

This invention relates to a method for encoding an input string A into an output string B, whose items an and bn belong to an alphabet S of M symbols sm, said method being characterised by providing an ordered arrangement of said M symbols sm of said alphabet S, by performing a scanning operation on said items a?n? of said input string A and in that, for each of said items ak, where k ELEMENT {0, 1, , N-1}, it includes arranging in decreasing order in an ordered arrangement vector O (whose items oj include the indexes I of items fI) the M items fI of an occurrence vector F of the symbols sm of the alphabet S in at least a portion W?k? &sube& A of T?k? items, establishing a permutation vector P consisting of M items pt, whose items are such as to fulfil the following relationship p?oj? = j and assigning to item bk of the output string B the symbol b?k? = s?E?(h?pt?=w) where w is the w-th index h?w? of the ordered succession H such as to fulfil the relationship a?k? = s?hw? and the enciphering function E(m) is an invertible function whose dominion and co-dominion are coinciding. The invention further relates to the concerned decoding method and the instruments and the apparatuses needed for performing the method.