Patent GB-1506143-A (GB)
Title: Method for producing cipher sequences consisting of binary symbol elements for enciphering binarily-coded data
IPC: H04L9/22
Filed: 1962-03-23
Abstract: 1506143 Data transmission R HELL 23 March 1962 [23 March 1961] 11324/62 Heading H4P A method of encoding symbols delivered by a teleprinter machine 1, each symbol containing seven positive and negative current pulses i.e. five data pulses and start and stop pulses, consists in producing a cipher pulse for each symbol pulse in a time which is negligible in comparison with the duration of a symbol pulse (20 m.secs.) and mixing the current symbol pulses according the Vernam Sign Rules and the resultant being transmitted as secret pulses. In Fig. I a time-setting device 3 delivers needleshaped pulses of + <SP>ve</SP> polarity, in synchronism with the pulses produced by the teleprinter 1, to a conductor 4, the first of these pulses setting a switch 5 to the working position thereby causing a pulse generator 7 to become operative through conductor 6. The generator 7 produces needle-shaped pulses of high frequency (e.g. 50 kc./sec.) through conductor 8 to the input of five electronic ring counters 9... 13 and to a counter 41, each pulse advancing each counter one step. The counters 9... 13 each have a different number of steps to make a complete rotation, the numbers being chosen so that no two of them have a common divisor. Each of the counters 9... 13 is assigned a programme by scanning its individual perforated row in a master programming strip 14. Each row assigns a positive or negative value, according to the presence or absence of holes, to the separate numerator steps of the corresponding counter, so that the output conductors 15... 19 receive a voltage which is alternating between positive and negative, according to the programmes. Conductors 15... 19 are connected to the first control inputs of coincidence storers 20... 24, the second control inputs being connected to the conductor 4. Each storer 20... 24 is a combination of an Andgate and a monostable switch and passes to the stable position when voltage is applied simultaneously to both its control inputs. Thus the positive pulses in conductor 4 switch only those storers having positive voltage applied to the first control inputs 15 ... 19. When a pulse occurs and before switch 5 has changed over and generator 7 has been connected, the counters 9...13 are located in specified initial positions and scan a specified configuration of the strip 14 so that positive or negative voltages are present at the outputs 15... 19 depending upon the presence or absence of holes. It is assumed that outputs 15, 16 and 19 have positive voltages and outputs 17, 18 negative voltages and hence the first pulse in conductor 4 switches storers 20, 21, 24 to the storage position while storers 22, 23 remain in the rest position. The output conductors 25... 29 of the storers 20... 24 are connected to a multiple super-imposition stage 30 and to a ring counter control stage 31. The stage 30 serves to transmit the voltages derived from the specified configuration of the strip 14 scanned at each pulse on the conductor 4 after mixing the outputs 25... 29 in successive pairs according to Vernam's Mixing Rules. E.g. the voltages at 25, 26 are mixed to produce a positive or negative pulse and this result is mixed with the voltage at 27... and so on. Finally, this result is mixed with a sixth input derived from a bi-stable switch 33, which, controlled by pulses from conductor 4 supplies alternately positive and negative pulses to the stage 30. The resultant from stage 30 produces voltage or no voltage on conductor 34 and represents a cipher pulse which is mixed in stage 35 with a pulse on a conductor 2 from the teleprinter 1, the secret pulse being delivered to the station to station line 36. The control stage 31 comprises a converter 37 having thirty-two outputs 42, 43, 44 &c. connected to thirty-two And-gates 38, 39, 40 &c. and also comprises the counter 41 having thirty-two outputs 45... 47 connected to the Andgates. At the moment under consideration, since storers 20, 21, 24 are prepared and storers 22, 23 are at their rest position, a voltage configuration 11001 = 25 exists at conductors 25... 29 and these produce a voltage at the 25th output conductor 43 of the converter 37 and the 25th And-gate 39 is prepared. The counter 41 advances one step from its null position upon each pulse from the generator 7 and at the 25th pulse it feeds a voltage to the 25th output conductor 46 whereby the 25th And-gate 39 opens and a voltage is supplied to conductor 48 so that switch 5 is changed back to its rest position. Conductor 6 is thus cut out and pulse generator 7 stops. Ring counters 9...13 have also been advanced by 25 steps to scan a different configuration of the strip 14 and they remain in that position in readiness for the second pulse on the conductor 4 from the device 3. Before each pulse on the conductor 4 a resetting pulse is produced on a conductor 49 to return any of these storers 20... 24 which are in their storage position back to their rest position and to return the counter 41 to its null position. Upon the second pulse to conductor 4 those storers which are receiving voltage applied to their first control inputs 15... 19 are again switched to the storage position and the cycle repeats as before. Modifications are described with reference to Figs. 2-4 (not shown).