Communication device that performs encrypted communication and communication system

Patent metadata

Field	Value
Publication number	US-11722294-B2
Application number	US-202117542399-A
Country	US
Kind code	B2
Filing date	Dec 4, 2021
Priority date	Jul 25, 2018
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

A communication device includes: a counter, a pseudo-random number generator, a symbol generator, a modulator, and a controller. The counter counts symbols transmitted to a correspondent device. The pseudo-random number generator generates a pseudo-random number corresponding to a count value of the counter. The symbol generator generates a transmission symbol from a transmission signal and the pseudo-random number. The modulator generates a modulated signal from the transmission symbol. When a disruption of a communication with the correspondent device is detected, the controller selects, from among a plurality of restoring times determined in advance, a restoring time for resuming the communication, and gives the counter a count value assigned in advance to the selected restoring time. The counter resumes a counting operation from the count value given from the controller when the communication device resumes a communication with the correspondent device.

First claim

What is claimed is:

1. A communication system that performs a communication between a first communication device and a second communication device,
the first communication device comprising;
a first clock;
a first counter configured to count symbols transmitted to the second communication device;
a first pseudo-random number generator configured to generate a pseudo-random number that corresponds to a count value of the first counter;
a symbol generator configured to generate a transmission symbol from a transmission signal and the pseudo-random number generated by the first pseudo-random number generator;
a modulator configured to generate a modulated signal from the transmission symbol generated by the symbol generator; and
a first controller configured to detect, when disruption of a communication with the second communication device is detected, a time at which the disruption of the communication is detected by using the first clock, to select a restoring time for resuming the communication based on the time at which the disruption of the communication is detected, the restoring time being selected from among a plurality of restoring times determined in advance, to give the first counter a count value assigned in advance to the selected restoring time,

the second communication device comprising:
a second clock;
a second counter configured to count symbols received from the first communication device;
a second pseudo-random number generator configured to generate a pseudo-random number that corresponds to a count value of the second counter;
a signal regenerator configured to regenerate the transmission signal from the modulated signal received from the first communication device by using the pseudo-random number generated by the second pseudo-random number generator; and
a controller configured to detect, when a disruption of a commutation with the first communication device is detected, a time at which the disruption of the communication is detected by using the second clock, to select a restoring time for resuming the communication based on the time at which the disruption of the communication is detected, the restoring time being selected from among the plurality of restoring times, to give the second counter a count value assigned in advance to the selected restoring time, wherein

when the first communication device resumes a communication with the second communication device, the first counter resumes a counting operation from the count value given from the first controller, and wherein
when the second communication device resumes a communication with the first communication device, the second counter resumes a counting operation from the count value given from the second controller, wherein
the symbol generator generates the transmission symbol by adding a cryptic noise that corresponds to a pseudo-random number generated by the first pseudo-random number generator to the transmission signal, and
the signal regenerator removes the cryptic noise from the modulated signal by using a noise removing signal that corresponds to a pseudo-random number generated by the second pseudo-random number generator.

2. The communication system according to claim 1 , wherein
the second communication device further comprises a remaining noise detector configured to detect a remaining noise that remains in the modulated signal after the cryptic noise is removed by using the noise removing signal, and
the first communication device further comprises a correcting unit configured to correct the transmission symbol based on the remaining noise.

3. The communication system according to claim 1 , wherein
the second communication device further comprises:
a remaining noise detector configured to detect a remaining noise that remains in the modulated signal after the cryptic noise is removed by using the noise removing signal; and
a correcting unit configured to correct the noise removing signal based on the remaining noise.

4. An optical transmission device, comprising:
a receiver configured to receive, from a correspondent device, an optical signal to which a cryptic noise that corresponds to an encryption key is added in the correspondent device;
a counter configured to count symbols received from the correspondent device;
a pseudo-random number generator configured to generate a pseudo-random number corresponding to a count value of the counter;
a noise removing signal generator configured to generate a noise removing signal that corresponds to the cryptic noise based on an encryption key that is the same as the encryption key and the pseudo-random number generated by the pseudo-random number generator;
a noise remover configured to remove the cryptic noise from the optical signal by using the noise removing signal;
a controller configured to select, when a disruption of a communication with the correspondent device is detected, a restoring time for resuming the communication based on a time at which the disruption of the communication is detected, the restoring time being selected from among a plurality of restoring times determined in advance, to give the counter a count value assigned in advance to the selected restoring time; and
a reporting unit configured to report, to the correspondent device, information relating to the optical signal from which the cryptic noise has been removed by the noise remover, wherein
the counter resumes a counting operation from the count value given from the controller when the communication device resumes a communication with the correspondent device.

5. An optical transmission method comprising:
receiving, from a correspondent device, an optical signal to which a cryptic noise that corresponds to an encryption key is added in the correspondent device;
counting symbols received from the correspondent device by using a counter;
generating a pseudo-random number corresponding to a count value of the counter;
generating a noise removing signal that corresponds to the cryptic noise based on an encryption key that is the same as the encryption key and the pseudo-random number;
removing the cryptic noise from the optical signal by using the noise removing signal;
selecting, when a disruption of a communication with the correspondent device is detected, a restoring time for resuming the communication based on a time at which the disruption of the communication is detected, the restoring time being selected from among a plurality of restoring times determined in advance;
giving the counter a count value assigned in advance to the selected restoring time; and
reporting, to the correspondent device, information relating to an optical signal from which the cryptic noise has been removed, wherein
the counter resumes a counting operation from the given count value when the communication device resumes a communication with the correspondent device.

Assignees

• Fujitsu Ltd

Inventors

• Oda Shoichiro
• Yoshida Setsuo

Classifications

• H04L9/0656 Primary

  Pseudorandom key sequence combined element-for-element with data sequence, e.g. one-time-pad [OTP] or Vernam's cipher · CPC title

• G06F7/582

  Pseudo-random number generators · CPC title

• H04B10/2507

  for the reduction or elimination of distortion or dispersion · CPC title

• H04L9/0847

  involving identity based encryption [IBE] schemes · CPC title

• H04L9/0662 Primary

  with particular pseudorandom sequence generator · CPC title