ENCRYPTED COMMUNICATION SYSTEM, TRANSMITTER AND RECEIVER USING SAME

• US 20120314867A1
• Filed: 01/17/2011
• Published: 12/13/2012
• Est. Priority Date: 02/15/2010
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Tomaru, Tatsuya
• Granted Patent: US 8,934,633 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: H04L 9/08 Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords network architectures or network communication protocols for supporting key management in a packet data network H04L63/06
• CPC Class Codes: H04L 9/0858 Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding

Abstract

High-security communications against information leakage as well as high-speed communications are realized using present optical fiber networks. The methods are as follows: (1) A seed key is shared between a transmitter and a receiver in advance. Random numbers are transmitted using carrier light accompanied by fluctuations and bases that are decided by random numbers. The transmitter and receiver compare a shared basis that is determined by the seed key with the random basis, and decompose the random numbers superimposed on each bit into two sequences, based on whether the shared basis coincides with the random basis or not. Error correction is processed for each sequence in the receiver, and then the random numbers are shared between the transmitter and the receiver. (2) The amount of the random numbers shared between the transmitter and the receiver is reduced to secret capacity through privacy amplification, and the resultant random numbers are used as a secret key. (3) Real data are encrypted with the obtained secret key, and they are transmitted and received.

Claims

1. A cryptographic communication system including a transmitter and a receiver connected with each other via a communication network,

wherein the transmitter stores the information of shared bases shared between the transmitter and the receiver and the information of random bases stored at or generated by only the transmitter,

wherein the transmitter includes

a function that generates a random number datum from four kinds of information that are the first random number generated by a random number generator, the second random number generated by another random number generator, the information of the shared basis, and the information of the random basis;

a function that generates a random number signal through superimposing the random number datum on the output from an electromagnetic wave source using the random basis, and that transmits the generated random number signal to the receiver via a first channel in the communication network; and

a function that generates a secret key from the first random numbers and the second random numbers, encrypts real data to be transmitted using the secret key, and transmits the encrypted real data to the receiver via a second channel in the communication network,

wherein the random number data are generated according to the rule that the first random number is adopted as a signal when the random basis coincides with the shared basis, and that the second random number is adopted as a signal when the random basis does not coincide with the shared basis,

wherein the receiver stores the information of the shared bases,

wherein the receiver includes

a function that judges the random basis and the random number value of the random number signal transmitted from the transmitter, compares the random basis with the shared basis, decides the random number signal as the first random number when the random basis coincides with the shared basis, and decides the random number signal as the second random number when the random basis does not coincide with the shared basis,

a function that differentiates between the first and second random numbers based on the judged results and produces the secret key from the differentiated first and second random numbers, and

a function that decodes the real data transmitted via the second channel into the pre-decrypted real data using the secret key.

2. The cryptographic communication system according to claim 1, wherein

the transmitter includes

a memory that stores the information of the shared bases and the random bases, a random number data generating unit, a random number signal transmitting unit, a secret key generating unit, and an encryptor, where

the random number signal transmitting unit has an electromagnetic wave source accompanied by fluctuations and a modulator, and generates the random number signals by modulating the output from the electromagnetic wave source accompanied by the fluctuations according to the random number data, and transmits the random number signals to the receiver,

the secret key generating unit generates the secret key from the first random numbers and the second random numbers, and

the encryptor encrypts the real data to be transmitted using the secret key and outputs the encrypted real data to the second channel in the communication network, and

the receiver includes

a memory that stores the information of the shared bases,

a detector that receives signal waves transmitted via the first channel,

a random number code reproducing unit that decides the random basis and the random number value of the received random number signal, compares the random basis with the shared basis, and decide and separate the first random number and the second random number according to the compared result,

a secret key generating unit that produces the secret key, and

a decryptor that decrypts the encrypted real data into the pre-encrypted real data using the secret key.

3. The cryptographic communication system according to claim 1, wherein

the electromagnetic wave source is a light source and

the first and second channels are optical channels.

4. The cryptographic communication system according to claim 1, wherein

the electromagnetic wave source is a high-frequency generator and

the first and second channels are electrical signal lines and free space with air.

5. The cryptographic communication system according to claim 2, wherein

the secret key generating unit in the transmitter is constructed from a unit for privacy amplification, and

generates the secret key by reducing the number of bits of the first and second random numbers that are the output from the random number generator.

6. The cryptographic communication system according to claim 2, wherein

the secret key generating unit within the receiver is constructed from a unit for privacy amplification and

produces the secret key by reducing the number of bits of the first and second random numbers.

7. The cryptographic communication system according to claim 1, further comprising an error correcting coding unit, wherein,

the first random numbers and the second random numbers are error-correcting-coded, and the information symbols part and the parity check symbols part are separated from each other,

the random number code that is the information symbols part is transmitted to the receiver via the first channel, and the parity check symbols part is transmitted to the receiver via the second channel.

8. The cryptographic communication system according to claim 1, wherein

the first random numbers and the second random numbers are error-correcting-coded and both of the information symbols part and the parity check symbols part are transmitted to the receiver via the first channel.

9. The cryptographic communication system according to claim 1, wherein

the random basis and the shared basis are compared with each other in pairs bit-by-bit and whether those bases coincide with each other or not determines whether to transmit the first random number or the second random number.

10. The cryptographic communication system according to claim 1, wherein

the random basis and the shared basis are compared with each other in pairs bit-by-bit, and the first random number is transmitted when the random basis coincides with the shared basis and the second random number is transmitted when the random basis does not coincide with the shared basis, and furthermore,

for the case that the shared basis does not coincide with the random basis, the same shared basis is repeatedly compared with next random basis until the shared basis coincides with the random basis.

11. The cryptographic communication system according to claim 1, wherein

the output signal from the transmitter is accompanied by phase fluctuations or intensity fluctuations, and

the output itself from the electromagnetic wave source includes the fluctuations or the fluctuations are added into the electromagnetic wave source or at a modulator.

12. The cryptographic communication system according to claim 1, wherein

the transmitter and the receiver share first and second secret keys in advance,

the transmitter has a first error correcting code encoder and a second error correcting code encoder,

the receiver has a first error correcting code decoder and a second error correcting code decoder,

in the transmitter, the first random number is encrypted using a first seed key and then is error-correcting-coded at the first error correcting code encoder, and the second random number is encrypted using a second seed key and then error-correcting-coded at the second error correcting code encoder, and

in the receiver, the signal decoded at the first error correcting code decoder is decrypted into the first random number by using the first seed key, and the signal decoded at the second error correcting code decoder is decrypted into the second random number by using the second seed key.

13. The cryptographic communication system according to claim 1, wherein

the first and second random numbers are binary, the random basis consists of two bases, and the signals are transmitted using net quaternary states.

14. The cryptographic communication system according to claim 1, wherein

the first and second random numbers are n-value and the random basis consists of m-bases, and the signals are transmitted using net n×

m-value states.

15. The cryptographic communication system according to claim 1, wherein

the random basis and the shared basis is compared with each other bit-by-bit in the transmitter, and when the random basis coincides with the shared basis, the first random number is adopted as a signal, and when the random basis does not coincide with the shared basis, the second random number is adopted as a signal, and furthermore, when the random basis does not coincide with the shared basis, the shared basis of the bit is compared with the random basis of the next bit, and when the random basis coincides with the shared basis, the first random number is adopted as a signal, and when the random basis does not coincide with the shared basis, the second random number is adopted as a signal, and each bit of the shared bases is repeatedly compared with the random bases until the shared basis coincides with the random basis, and

the random basis and the shared basis are similarly compared bit-by-bit in the receiver, and when the random basis coincides with the shared basis, the signal of the bit is adopted as the first random number, and when the random basis does not coincide with the shared basis, the signal of the bit is adopted as the second random number, and furthermore, when the random basis does not coincide with the shared basis, the shared basis of the bit is compared with the random basis of the next bit, and when the random basis coincides with the shared basis, the signal of the bit is adopted as the first random number, and when the random basis does not coincide with the shared basis, the signal of the bit is adopted as the second random number, and each bit of the shared bases is repeatedly compared with the random basis until the shared basis coincides with the random basis.

16. The cryptographic communication system according to claim 1, wherein

the transmitter includes a first random number generator, a first error correcting code encoder, a second random number generator, a second error correcting code encoder, a third random number generator, a first light source, a first modulator, a unit for first privacy amplification, a unit for second privacy amplification, an encryptor, and an optical transmitter unit having a second light source and a second modulator,

the receiver includes a first detector, a first error correcting code decoder, a second error correcting code decoder, a unit for first privacy amplification, a unit for second privacy amplification, a second detector, and a decryptor,

the transmitter and the receiver share a seed key formed of random numbers in advance, and the seed key provides the transmitter and the receiver with the shared bases,

in the transmitter,

the output from the first random number generator is error-correcting-coded as the first random number signals at the first error correcting code encoder, and the first random number signals are separated into information part and its redundant part, the former being defined as the first random number code and the latter being defined as the first check symbols, and

the output from the second random number generator is error-correcting-coded as the second random number signals at the second error correcting code encoder, and the second random number signals are separated into information part and its redundant part, the former being defined as the second random number code and the latter being defined as the second check symbols,

the output from the third random number generator is used as the random bases for transmitting the first and second random number codes, where the first random number code is adopted as a signal when the random basis coincides with the shared basis, and the second random number code is adopted as a signal when the random basis does not coincide with the shared basis,

the signal is superimposed on the output light from the first light source at the first modulator using the random basis and the superimposed light is defined as first signal light, the output light from the first light source is accompanied by fluctuations or is added fluctuations at the first light source or the first modulator, and the first signal light is output to the first optical channel,

the unit for first privacy amplification reduces the number of bits of the random number signals that are the output from the first random number generator and the unit for second privacy amplification reduces the number of bits of the random number signals that are the output from the second random number generator,

the encryptor encrypts real data using the output from the units for first and second privacy amplification as a secret key,

the encrypted real data and the first and second check symbols are multiplexed, and the multiplexed real data are superimposed on carrier light and the carrier light is output to the second optical channel from the optical transmitter unit as second signal light, and

in the receiver,

the second signal light is received with the second detector, and the encrypted real data and the first and second check symbols are separated from the received signals,

the first signal light is received with the first detector,

the random basis and the signal value are judged, the received random basis is compared with the shared basis, the signal is treated as the first random number code when the received random basis coincides with the shared basis, the signal is treated as the second random number code when the received random basis does not coincide with the shared basis, the first random code is parity-checked using the first check symbols, a basis-judgment error is checked according to the parity check, the error-judged basis is corrected if there is, and according to the correction the judgment on whether the signal is the first random number code or the second random number code is corrected, where each judged value of the code is also corrected,

the first random number code whose basis-judgment-error is corrected is decoded at the first error correcting code decoder using the first check symbols, and the number of bits of the decoded first random number code is reduced at the unit for first privacy amplification,

the second random number code whose basis-judgment-error is corrected is decoded at the second error correcting code decoder using the second check symbols, and the number of bits of the decoded second random number code is reduced at the unit for second privacy amplification,

the outputs from the units for first and second privacy amplification are used as a secret key, and

the encrypted real data are decrypted into the pre-encrypted real data at the decryptor using the secret key.

17. A transmitter of a cryptographic communication system connected to a receiver via a communication network, comprising:

a random number generator and an electromagnetic wave source, wherein

the transmitter stores the information of shared bases shared between the transmitter and the receiver as well as random bases that are stored or generated only at the transmitter,

the random number generator has a function that generates at least first random numbers and second random numbers, and

the transmitter includes;

a function that generates random number data by adopting the first random number as a signal when the random basis coincides with the shared basis and by adopting the second random number as a signal when the random basis does not coincide with the shared basis,

a function that generates random number signals by superimposing the random number data on the output from the electromagnetic wave source using the random bases and transmits the generated random number signals to the receiver via a first channel in the communication network;

a function that generates a secret key from the first random numbers and the second random numbers, encrypts real data to be transmitted using the secret key, and transmits the encrypted real data to the receiver via a second channel in the communication network.

18. The transmitter according to claim 17, wherein

the electromagnetic wave source is a light source, and

the first and second channels are optical channels.

19. The transmitter according to claim 17, wherein

the first and second random numbers are n-value and the random bases consist of m-bases, and the signals are transmitted using net n×

m-value states.

20. A receiver of a cryptographic communication system connected to a transmitter via a communication network having first and second channels, wherein the receiver:

stores the information of the shared bases shared between the receiver and the transmitter, and

includes

a function that judges a random basis and a random number value of the random number signal that is transmitted via the first channel from the transmitter and received, compares the random basis with the shared basis, decides a random number value as a first random number when the random basis coincides with the shared basis, and decides the random number value as a second random number when the random basis does not coincide with the shared basis,

a function that produces the same secret key as a secret key generated in the transmitter from the judged first and second random numbers, and

a function that decrypts real data transmitted from the transmitter via the second channel into pre-encrypted real data using the secret key.