| 摘要 |
A ciphering system comprising a ciphering device having an input (1) for a sequence of bits to be ciphered, and output (2) for the ciphered bit sequence, and a mixing unit (3) connected between the input (1) and the output (2). The mixing unit receives both the bit sequence to be ciphered and a sequence of code bits for ciphering the bit sequence and, by a mixing operation, generates the ciphered bit sequence. The output of the mixing unit (3) is connected to a code unit (4) for generating code bits. The code unit (4) comprises a memory (5) containing code bits and addressed with bits from the ciphered bit sequence for generating code bits. The ciphering device further has means (7) for selecting whether a bit in the bit sequence to be ciphered should be mixed with a code bit or not, and means (6) for selecting which bits in the ciphered bit sequence should be used for addressing the memory. These means are controlled by a programmable control unit (8). The deciphering device of the ciphering system is conceived in the same manner as the ciphering device, with the exception that the input of the code unit receives input signals from the input of the deciphering device. Since the ciphering and the deciphering device are designed in the same manner and their different units receive the same information, these devices will be automatically synchronized after an interruption. Further, the ciphering system is very rapid and the delay of the transmitted information is negligible. |
