| 摘要 |
1500680 Data transmission; ciphering SIEMENS AG 18 Sept 1969 [22 Nov 1968] 46157/69 Heading H4P A cipher system for ciphering or deciphering an applied signal by the steps of combining the applied signal with a first intermediate cipher signal obtained from a predetermined position in a sequence produced by a cipher bit generator to obtain a first resultant, stepping the generator to a further position in the sequence by a number of steps determined by the content of the first intermediate cipher signal, and combining the first resultant with the further intermediate cipher signal obtained from the further position. Fig. 1 illustrates a system for ciphering plainlanguage signals in a five-element binary code by adding intermediate cipher signals from a quasirandom cipher bit sequence produced by a cipher bit generator. The generator is set to a predetermined start position An in a sequence SB and an intermediate cipher signal SZ1 having the binary value BV1 of 01101 (=decimal 13) is obtained. This signal has an alphabetical significance of "F". To obtain the further intermediate cipher signal SZ2 the cipher bit generator is stepped by the number of steps corresponding to the value of signal SZ1, i.e. it is stepped on by 13 bits to a position such that the signal SZ2 has a binary value BV2 of 00101 (=decimal 5) and an alphabetical significance of "S". The binary value of the applied plain-language signal KZ is added to the binary value BV1 to the mode 32. For example, if the signal KZ is the letter "A" having a binary value BV3 of 00011 (= decimal 3) the resultant BV4 = 13 + 3 = 16 or 10000 in binary notation. The resultant BV4 is added to BV2 to obtain BV5=16+5=21 or 10101 in binary notation, the latter being used as the ciphered signal VZ with the alphabetical significance "Y". The system for deciphering is similar (Fig. 2, not shown) except that subtraction takes the place of addition. |
