Patent GB-914813-A (GB)
Title: Improvements in or relating to arrangements and apparatus for encoding and decoding information to be transmitted respectively from or on to a teleprinter
IPC: H04L9/18
Filed: 1959-06-22
Abstract: 914,813. Teleprinter code-ciphering and deciphering. HELL, R. June 22, 1959 [June 21, 1958], No. 21317/59. Class 40 (3). An arrangement for ciphering and deciphering information transmitted by a 5-unit teleprinter code and using random 5-unit signals for ciphering the plain text message and deciphering the secret transmission comprises pulse generators which have respective cycles with numbers of steps which are all prime to one another and produce varying sets of pulses which are compared with predetermined pulse combinations, the required identity detection being utilized to form a pulse of the random 5-unit ciphering signal, the pulses produced which are of two different kinds being stored until five have been derived to be combined with the 5-unit plain or ciphered message at the transmitter or receiver respectively. The present modification comprises the provision of two members for the storing of alternate 5-unit cipher signals, the signal elements forming a store being released under control of the start element of a teleprinter combination to be associated multiplicatively with the five elements of the cipher signal, whilst a pulse generator also rendered operative by the start element to control the generation of the ciphering pulses for the other store is put out of operation when the fifth ciphering element has been stored. In the arrangement shown, pulses produced by five cyclic generators 39 ... 43 having numbers of steps which are prime to one another are passed to a detecting arrangement 49 in which predetermined pulse combinations are set up. The signal detections pass pulses for storage in sequential stages of storage members I, II under control of a generator 35 released under control of the start element of the combination from the teleprinter 1 and effectively cut-off when the storage member I or II is complete. When a complete cipher signal has been registered in the store I, outputs over conductor 11 and from the right-hand section of switch element 61 open gate 12 to operate switch device 13 to provide a voltage pulse over conductor 14 to the inputs of a first set of " AND " gates, such as 9, 10, associated with the first store I(6). Positive outputs on, for example, leads 7, 8 open gates 9, 10 and also " OR " gates 15, 16, providing one input to two pulse " AND " gates 19, 20. The start element of the signal from the teleprinter 1 operates switch 21 to provide a pulse over lead 22 to set into operation a multivibrator 23 producing, at intervals of 20m. sees., pulses applied to a counter 24 which opens the gates, e.g. 19, 20 already primed by voltages from gates 15, 16 to pass pulses over the conductor 4 to the mixer 3 producing the ciphered code combination for the outgoing line 5. The seventh pulse via the counter 34 and lead 28 operates switch member 21 to cut-off the multivibrator 23 and via gate 29 to erase the cipher code combination set up in the store I(6). Also the pulse from the gate 29 operates the switch element 13 so that its left-hand side conducts and a pulse over conductor 50, when a 5-unit signal has been registered in the store II, opens gate 60, and changes over switch 61 so that a pulse over lead 62 opens these gates, such as 64, 65, 66 which receive positive pulses from the cipher code stored in the store II(54), and via gates 15, 16 and gates 19, 26, 20 pass the corresponding pulses to the mixer 3 under control of the counter 24 operated in response to the starts element of the next signal from the teleprinter 1. Generation of cipher signals for the stores, I, II. Sets of five pulses derived from five cyclicallyoperating generators 39 ... 43 having steps or stages in numbers which are prime to one another are applied to a circuit 49 arranged to detect predetermined 5-unit code combinations, generally as described in Specification 907,412. The elements 39 ... 43 are stepped by pulses from a generator 35 via a two-input " AND " gate 34 primed by a voltage from a switch device 32 when its right-hand side is rendered operative by the operation of switch element 21 in response to the start element of a signal from the teleprinter 1. When a predetermined code combination is detected by the circuit 49, a pulse is passed via an " OR " gate 50 and through " AND " gate 51 primed by pulses from " AND " gate 34 and differentiator 52 to the input of the store I or II, which, in combination, are operated as a ten-stage cyclic counter by the pulses over conductor 53. A switch member 71 is changed over in response to each pulse from the differentiator 52 so that, depending on the condition of the member 71, a positive or negative pulse is registered in the store I(6) or II(54) when a pulse from detector 49 passes through gates 50, 51. When the store I or II has registered a 5-unit cipher signal a pulse over conductor 11 or 55 respectively and via differentiator 70, 56 passes through " OR " gate 57 to operate switch element 32 so that the gate 34 is closed to the pulses from the generator 35. The apparatus is brought into operation by closure of a key 73 to generate the first cipher signal for the store I(6).