The invention relates to a method for producing a coated substrate body by chemical vapor deposition at least on one layer made of a carbonitride of a metal of IVa-Vla-groups of the periodic table, wherein a monocyclic hydrocarbon is used in the gas atmosphere during the deposition, in addition to a nitrile. The applicator barrel includes a barrel body having an outer surface. The time-reversed channel response is convolved with an information signal that when transmitted in a coordinated fashion from the group of transmitters, the signals arrive at each receiver in the group of distant receiving communication devices at approximately the same time where the signals coherently combine, thereby increasing signal power at the receivers. The method further comprises generating a key tree having a plurality of levels, wherein the keys for the lowest level of the key tree are the common keys generated for each leader and wherein the keys for each successive layer are generated by combining pairs of keys from lower levels of the key tree.