GB973536A - Ciphering systems - Google Patents

Abstract

973,536. Telegraphy. GRETAG A.G. Sept. 24, 1962 [Oct. 2, 1961], No. 36294/62. Heading H4P. A cipher pulse generator 20, Fig. 1, comprises a chain of binary elements 32 in which consecutive elements interact so that at each step on the average at least half of the elements alter, outputs from the chain being taken to a mixing circuit 24 delivering a cipher pulse programme for mixing at 14 with the clear message, e.g. from a teleprinter 10. An identical cipher pattern generator 22 is provided at the receiver and mixer 18 re-constitute the clear message for teleprinter 12. In the form of Fig. 2, the binary elements 100-108 are simultaneously switched by input pulses on line 110. Each element is connected through a delay 124 to the input S of succeeding elements. The inputs are applied through And-not gates 126-132 and inputs to these are through And gates 134-138. The arrangement is such that at each pulse on the input 110 the setting pattern of the elements 100-108 changes substantially according to an arbitrary code. In another arrangement, Fig. 3, the elements 212-218 are switched by the change-over of preceding elements Or gates 234 being provided in the inputs to elements 214-218. The elements change in consecutively after each input pulse on the lead 230. This reduces the rate of operation. In another form, Fig. 4, a chain of elements 310-318 are connected as a binary scale counter, the outputs have " 1 " and " 0 " outputs which are gated with the outputs of a flip-flop 350 set and reset at each input pulse on the lead 354. At alternate steps of the counter the outputs on leads 320-328 represent the binary scale value in the counter or its inverse. Specification 951,174 is referred to.