The invention relates to a method for data transmission, comprising the following steps: first data from a stochastic process (114) is inputted into at least a first and a second subscriber (102, 104; 402, 404; 502, 504, 506, 508, 510, 512, 516) of a communication network (100, 106; 400, 406; 500, 514, 518); and a symmetrical key (S1, S2) is produced on the basis of the first data in both the first and the second subscriber, and stored in the same, for an encoded data transmission between said subscribers.