Abstract: Prior to the sale of a personal communication terminal, a secret key is generated and stored in the personal communication terminal in accordance with an application made from the manufacturer to the carrier. At this time, the communication between the manufacturer and the carrier is performed in the form of secret communication with a signature that conforms to a public key system. After the sale, an identification number encrypted with the same key as the secret key is transmitted to the personal communication terminal in accordance with an application made from the user to the carrier. Using the stored secret key, the personal communication terminal decrypts the received identification number for storage therein.

Abstract: An encryption communication system including: a communication center having at least a key information generating unit for generating key generating information used for encryption communication; and a plurality of user computers, each interconnected by a plurality of paths through the communication center, and each having at least an encryption key generating unit and an encryption processing unit. The communication center generates the key generating information Z based on predetermined modulo arithmetic formula. The user computer sends a password PW to the communication center, receives the key generating information therefrom, and generates an encryption key K used between the user computer and another party's computer based on predetermined modulo arithmetic formula.

Abstract: Disclosed is a voice band splitting scrambler. To simplify the hardware thereof, the apparatus comprises a band splitting unit (11) for splitting an input voice signal into a plurality of band channels, and a scrambled voice signal generating unit (13) for carrying out spectrum-inverting and band-relocating operations on the respective channels to generate a scrambled voice signal. The scrambled voice signal generating unit (13) includes a modulating unit (15) for band-relocating the respective channels by noninverting carriers of inverting carriers set in different bands respectively; and an adding unit (17) for adding the signals of the noninverting channels and the signals of the inverted channels to each other.

Abstract: Disclosed is a secret speech equipment for ensuring the secrecy of an analog voice signal, and used in voice communication systems such as an analog telephone and mobile radio. The equipment comprises a sub-band signal generating unit for treating input digital samples as frequency-multiplexed signals of voice spectra, to split the frequency-multiplexed signals into a plurality of frequency bands, and thus obtain sub-band signals of the frequency bands, a sub-band signal permutating unit for permuting the sequence of the sub-band signals, and a sub-band signal multiplexing unit for multiplexing the permutated sub-band signals.