Method and device for the coded transmission of messages

A system for encoding messages through the transposition of selected message elements, comprising at least one element exchanger means provided at the transmitting and at the receiving end for exchanging pairs of elements and at least one control addition means (FIGS. 11, 13);

• said element exchanger means having an input for receiving message elements and an output for delivering exchanged elements for transmission and containing signal retarder means having a constant delay tine T for delaying elements selectively applied thereto, and first and second electronic changeover switch means respectively positioned at the input and output of the retarder means;
• said first changeover switch means having first and second operating positions for respectively connecting the input of the element exchanger means directly to the output of the element exchanger means and for connecting the input of the retarder means to the input of the exchanger means;
• said second changeover switch means having first and second operating positions for respectively directly connecting the output and input of the retarder means and for connecting the output of the retarder means to the output of the element exchanger means;
• said first and second electronic changeover switches being normally maintained in their first positions;
• means for generating a quasi-statistical pulse train;
• said control addition means containing an electronic interrupter means for selectively cancelling individual pulses of said statistical pulse train (cipher signal) said interrupter means having a control input for cancelling a pulse at its output upon receipt of a control inhibit pulse;
• said interrupter means being actuated through pulse retarder means having a delay time T for delaying pulses at an output of said interrupter means and replacing the delayed pulses to the control input of said interrupter means so that no pulses which have a mutual spacing T appear at the output of the interrupter;
• the output pulses of the interrupter being coupled to said first and second electronic changeover switch means of the element exchanger means to move the said first and second electronic changeover switch means to their second positions.

Means for the permutation of message elements in accordance with a predetermined program comprising:

• an element exchanger having an input for receiving the message elements to be permutated and an output for delivering permutated elements;
• first and second retarder means each having a delay time T.sub.1 for delaying elements applied thereto;
• first and second sets of changeover switches respectively associated with said first and second retarder means and having a first normal position for connecting the inputs of said first and second retarder means to said exchanger means input and for connecting the outputs of said first and second retarder means to said exchanger means output, and a second operative position for connecting the output of each retarder means to its input;
• an auxiliary message element path;
• a third set of switch means having a first normal position for connecting said auxiliary path between said exchanger means input and output and having a second operative position for connecting the output of the auxiliary path to its input;
• means for operating said first, second and third sets of switch means so that only one of said sets of switch means is in the operative position during the interval of any message element.

A device for encoding or decoding messages by transposing selected pairs of message elements comprising:

• delay means having an input and an output;
• a direct signal path for passing signals between its input and the output of the device with no delay;
• a feedback signal path for passing signals between the output and the input of said delay means;
• first switch means for receiving said message in serial fashion and for selectively coupling said message either to said delay means input when in a first condition or to said direct signal path input when in a second condition to cause the message to appear at said device output with no delay;
• second switch means for selectively coupling the delay means output to said device output when in a first position or to said feedback signal path when in a second condition;
• control means for operating both said first and second switch means;
• said control means comprises means for generating a random pulse pattern;
• means for sampling successive pulses in said random pulse pattern to inhibit selected ones of the pulses, so that a pulse interval is always followed by a no pulse interval, and applying the resulting pulses as control signals to said first and second switch means.

A device for altering a message by transposing selected ones of the message elements said device comprising;

• an input for receiving the message to a utilization device after undergoing element transposition;
• first and second and third signal paths;
• at least two of said signal paths having means for imparting a delay to message elements applied thereto, while the remaining signal path imposes no delay to message elements applied thereto;
• first, second and third feedback paths;
• first, second and third switch means respectively associated with one of said signal and feedback paths whereby each switch means, either couples a feedback path across its signal path when in a first switch condition or couples the signal path between said input and said output when in a second switch condition;
• control means for operating said first, second and third switch means so that no more than one of said switch means is in said first condition at any given time.