Method and apparatus for synchronizing a receiver end-key generator with a transmitter end-key generator

A method of synchronizing a receiver end-Key Generator with a transmitter end-Key Generator, comprising the steps of:

• a. coupling each of the Key Generators with an associated counter such that the counter state of each counter is characteristic of a position of a Key sequence produced by the associated Key Generator;
• b. forming each counter state from the preceding counter state in accordance with a predetermined formation principle;
• c. transmitting the counter state of the counter of the transmitter end-Key Generator to the receiver end;
• d. comparing the thus transmitted counter state with the counter state of the counter of the receiver end-Key Generator;
• e. upon determination of a difference between both counter states, forwardly advancing the receiver end-Key Generator until the difference between the counter states is reduced to null;
• f. said forwardly advancing step (e) comprising:
• i. forwardly advancing in steps the receiver end-Key Generator when the determined difference between the counter states is smaller than a threshold value;
• and
• ii. forwardly advancing the receiver end-Key Generator in jumps encompassing a multiplicity of individual advancing steps when the difference between the counter states exceeds said threshold value;
• g. and producing at the receiver end by means of the formation principle for forming the counter states the next successive counter states which are to be expected owing to the received counter states of the transmitter end-counter, comparing such counter states produced at the receiver end with the correspondingly received counter states, and upon determining a difference of the receiver end produced counter state and the correspondingly received counter state determining the correct counter state based upon the majority of the coinciding places of the counter states.