JPS6411437A - Method for scrambling signal of cipher communication equipment - Google Patents

Abstract

PURPOSE:To speedily cope with data transmission by performing arithmetic operation when no communication is made and generating a specific cipher key set, and selecting and using an optional key at each time when it is necessary. CONSTITUTION:A controller 9 and an arithmetic unit 5 specify the number (m) of groups in a state of conversion from a feedback function as a kind stored in a storage device 8 with the output of a random number generator 6. Then (m) groups are selected from the kind feedback function according to the random number and all-cycle- sequence inspection is performed to judge whether or not a feedback function obtained by converting all of the groups into complements provides all cycle sequences again. When not, a return to the start is made and when such a combination that all cycle sequences are obtained is obtained, it is confirmed whether or not there is a request for a cipher communication; and this operation is repeated until the communication request is generated to generate a combination of (m) feedback functions to be substituted, which are stored in K areas of a storage device 7 by K. When the communication request is generated, one of K usable feedback function sets to be converted is selected at random according to the signal of the generator 6 and set as a key in a cipher circuit.