1. A binary multiplication unit havving a multiplication time substantially higher than the time separating the entering of two successive multiplicand words into the unit, said binary multiplication unit comprising: (a) a multiplicand storage means for successively storing multiplicand words and a multiplier storage means for permanently storing a predetermined multiplier word; (b) means for partitioning each multiplicand word into a plurality of multiplicand subwords following one another in increasing binary weight, each multiplicand subword comprising at least one binary element; (c) means for deriving from each multiplicand subword and the following multiplicand subword a shifted multiplicand subword obtained by omitting the bit of lowest binary weight of the multiplicand subword and adding thereto, as bit of highest binary weight, the bit of lowest binary weight of the following multiplicand subword; (d) means for multiplying said shifted multiplicand subwords by the first bit of said multiplier word and thus obtaining first subproducts; (e) means for respectively multiplying said multiplicand subwords by the successive bits of the multiplier word starting from the second bit of said multiplier word and thus obtaining second, third and following subproducts associated with said multiplicand subwords; (f) means for adding together said first and said second subproducts and thus obtaining subproduct sums following one another in increasing binary weight; (g) means for deriving from each subproduct sum and the following subproduct sum a shifted subproduct sum obtained by omitting the bit of lowest binary weight of the subproduct sum and adding thereto, as bit of highest binary weight, the bit of lowest binary weight of the following subproduct sum; (h) means for respectively adding said third and following subproducts associated with each multiplicand subword respectively to third and following shifted subproduct sums deriving from the subproduct sum associated with the preceeding subproducts of the multiplicand subword and the subproduct sum associated with the preceeding subproducts of the following multiplicand subword; and (i) means for deriving said third and following shifted subproduct sums, each subproduct sum being obtained by omitting the bit of lowest binary weight of the subproduct sum associated to a given miltiplicand subword and adding thereto, as bit of highest binary weight, the bit of lowest binary weight of the subproduct sum associated with the following multiplicand subword.