or the like second subscriber 300 may thereby be battery powered in particular and accordingly also have a transmitter and receiver unit fig2 schematically shows a functional sequence of a method according to the present invention in a preferred specific embodiment first subscriber 200 has a first bit string 201 second subscriber 300 has a second bit string 301 these two bit strings 201 and 301 may thereby have been generated from physical properties of channel 110 of communications network 100 the generation of such bit strings from physical properties of the channel was briefly described at the outset and is generally known it is therefore not explained further in the following the two bit strings 201 and 301 may thereby be preferably used as the shared secret key for a secure communication between first subscriber 200 and second subscriber 300 in communications network 100 to this end however it is necessary to reconcile the two bit strings and in some instances to also correct one of the two bit strings it is noted in this regard that bit string 301 differs exemplarily from bit string 201 in the fourth bit from the left in a step s 1 first subscriber 200 now selects a block 211 having a number of exemplarily eight bits beginning with the first bit from the left of bit string.