Method and apparatus for generating a shared secret of predetermined length

A method (30) for generating a shared secret, characterized by the following features: - sends in a first superposition stage (31) (33), the first node a first bit sequence, the second node sends (34) largely in synchronism therewith, a second bit sequence and the first node and the second node detect simultaneously an effective third bit sequence, to which is overlaying the first bit sequence and the second bit sequence on the medium in places, - in a second superposition stage (32) sends (35) the first node, the first bit sequence in places inverted, the second node sends (36) largely in synchronism therewith the second bit sequence locally inverted and the first node and the second node detect simultaneously an effective fourth bit sequence to which the inverted first bit sequence and the second inverted bit sequence overlap, - the first node and the second node link (37), the third bit sequence in places with the fourth bit sequence to a fifth bit sequence, - the first node and the second node complement (38) includes a first secret by the first node deletes bits of the first string and the second node corresponding bits of the second bit sequence numbers match in value according to the fifth bit sequence and - the superimposition of phases (31, 32), the link (37) and replenishing (38) of the first secret to be repeated (39) until the first secret reaches a predetermined first length.