| 摘要 |
System for encrypting and decrypting narrow-band analog signals comprising, in transmitting and receiving stations, means (2, 32) of digitising a respectively uncoded and encrypted incoming analog signal, and of dividing the resulting data into frames with a specified number of bits, each frame being divided into a certain number of packets with a specified number of bits, the said transmitting and receiving stations furthermore comprising a psuedo-random code generator (7, 37), means (13, 43) of synchronising the two pseudo-random code generators with one other, and means of permuting the packets of a frame, characterised in that the said system furthermore comprises means (15, 45) for synchronously inverting the spectrum of the transmitted and received signals, and in that the pseudo-random code generators (7, 37) have a cycle of (N+1) random bits, of which N bits are used to control the permuting of the packets and one bit controls the spectrum inversion. <IMAGE> |
