Abstract: A compressed-code generating method that is used for compressing information on characters including numerical data, sound and images, and a compressed-code expanding method that is used for restoring and expanding the compressed code generated by using the compressed-code generating method to the original information. Bit strings {y}1 and {y}2 are obtained respectively from a bit string {y} of information to be compressed. A reversible loop that exists in chaos is operated to these obtained bit strings, thereby to execute a reversible compression/expansion of the information using the chaos.

Abstract: Each of plural CPUs enciphers a plaintext code which is a secrecy object according to chaos block encryption and then enciphers it according to chaos stream encryption. Then, it transmits an obtained cipher code through communication line. On the other hand, each of plural CPUs that received the cipher code synchronously restores the received cipher code according to chaos stream encryption and then restores according to chaos block encryption thereby to obtain an original plaintext code.

Abstract: A chaos-generating loop includes a one dimensional mapping circuit (13) with non-linear input-output characteristics for generating chaos, a linear or non-linear AD converter (15) for converting an analog output of the one dimensional mapping circuit (13) to digital form, a sample-and-hold circuit (17) for holding and outputting the digitally converted value from the AD converter (15), in response to an external clock (C), and a linear or non-linear DA converter (19) for converting an output of the sample-and-hold circuit (17) to analog form and outputting this analog signal to the one dimensional mapping circuit (13), and a decoder for outputting a chaos stream in response to the output of the sample-and-hold circuit (17).

Abstract: Arithmetic operation is started by substituting an initial value x(0) for a logistic mapping x(t+1)=4x(t){1x(t)} which is a symmetrical nonlinear mapping. The resultant value is again input into the logistic mapping x(t+1)=4x(t){(1−x(t)}, based on an feedback x(t)=x(t+1). This operation is repeated to obtain time series x(t)−t. Isomorphic transform and quantization corresponding to the time series x(t)−t is obtained based on y(t)=[{2/&pgr;·arc sin {square root over (0)}x(t))}·2n] while a quantizing resolution n=1 is substituted for y(t)=[{2/&pgr;·arc sin {square root over (0)}x(t)}·2n]. A time series y(t)−t is determined from the obtained isomorphic transform and quantization. A spread spectrum signal having, as a period thereof, binary code sequence y(t) arbitrarily sampled from the time series y(t)−t is generated.

Abstract: On a transmitter side, an enciphering means enciphers a plaintext code according to stream enciphering method having a feature in selecting the cycle of a PN signal and then a transmitting means transmits the cryptographic code. On the other hand, on a receiver side, a deciphering means restores the cryptographic code enciphered in the above described procedure to an original plaintext code by carrying out exclusive-OR operations again.

Abstract: Each of plural CPUs enciphers a plaintext code which is a secrecy object according to chaos block encryption and then enciphers it according to chaos stream encryption. Then, it transmits an obtained cipher code through communication line. On the other hand, each of plural CPUs that received the cipher code synchronously restores the received cipher code according to chaos stream encryption and then restores according to chaos block encryption thereby to obtain an original plaintext code.