Encrypting conversion apparatus, decrypting conversion apparatus, cryptographic communication system, and electronic toll collection apparatus

• US 20030026430A1
• Filed: 09/26/2002
• Published: 02/06/2003
• Est. Priority Date: 05/29/1998
• Status: Abandoned Application

• Current Assignee: Kazuo Takaragi, Makoto Aikawa, Shigeru Hirahata, Yoshimichi Kudo
• Original Assignee: Kazuo Takaragi, Makoto Aikawa, Shigeru Hirahata, Yoshimichi Kudo
• Inventors: Aikawa, Makoto, Kudo, Yoshimichi, Takaragi, Kazuo, Hirahata, Shigeru
• Application Number:
  US10/254,581
• Publication Number:
  US 20030026430A1
• Time in Patent Office: Days
• US Class Current: 380/277
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 9/002 Countermeasures against attacks on cryptographic mechanisms network architectures or network communication protocols for protection against malicious traffic H04L63/1441
• CPC Class Codes: H04L 9/0618 Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation

Abstract

An encrypting conversion apparatus, a decrypting conversion apparatus, a cryptographic communication system and an electronic toll collection apparatus are provided which are capable of changing algorithms of cryptographic conversion to hide the algorithm in use from a third party so that the apparatuses and system are resistant against a cryptographic attack from the third party and can operate at high speed. In the cryptographic communication system.

Claims

1. An encrypting conversion apparatus for inputting at least one cipher key, at least one algorithm parameter, and plain text data and outputting cipher text data, said encrypting apparatus comprising:

a plurality stage of encrypting conversion means for executing each of an exclusive logical sum operation, a cyclic shift operation and an addition operation at least once,

wherein;

said encrypting conversion means includes at least one of each of first to third operation means, said first operation means executes either an exclusive logical sum operation or an addition operation of input data and a portion of data generated from data of the cipher key, said second operation means executes either an exclusive logical sum operation or an addition operation of input data and a portion of data determined by the algorithm parameter, and said third operation means cyclically shifts input data by the number of bits determined by the algorithm parameter; and

conversions which use combinations of a plurality stage of consecutive encrypting conversion means optionally selected from all of said encrypting conversion means and use the same input data and the same algorithm parameter, are all different.

2. A decrypting conversion apparatus for inputting at least one cipher key, at least one algorithm parameter, and cipher text data and outputting plain text data, the apparatus comprising:

a plurality stage of decrypting conversion means for executing each of an exclusive logical sum operation, a cyclic shift operation and an addition operation at least once,

wherein;

said decrypting conversion means includes at least one of each of first to third operation means, said first operation means executes either an exclusive logical sum operation or an addition operation of input data and a portion of data generated from data of the cipher key, said second operation means executes either an exclusive logical sum operation or an addition operation of input data and a portion of data determined by the algorithm parameter, and said third operation means cyclically shifts input data by the number of bits determined by the algorithm parameter; and

conversions which use combinations of a plurality stage of consecutive decrypting conversion means optionally selected from all of said decrypting conversion means and use the same input data and the same algorithm parameter, are all different.

3. A cryptographic communication system with a common key algorithm for communication between a transmitter apparatus and a receiver apparatus having a same cipher key, the transmitter apparatus encrypting a plain text by using the cipher key to acquire and transmit a cipher text, and the receiving apparatus decrypting the received cipher text by using the cipher key to recover the plain text, wherein:

said transmitter apparatus includes encrypting conversion means and first algorithm key storing means;

said receiver apparatus includes decrypting conversion means and second algorithm key storing mean;

a conversion algorithm to be executed by said encrypting conversion means of said transmitter apparatus is determined by a first parameter stored in said first algorithm key storing means of said transmitter apparatus;

a conversion algorithm to be executed by said decrypting conversion means of said receiver apparatus is determined by a second parameter stored in said second algorithm key storing means of said receiver apparatus; and

the cipher text encrypted by said transmitter apparatus by using the cipher key can be correctly decrypted by said receiver apparatus by using the cipher key, only if the cipher key as well as the first and second parameters used by said transmitter and receiver apparatuses is same.

4. A cryptographic communication system according to claim 3, wherein said transmitter apparatus uses a predetermined specific third parameter as the first parameter, and said receiver apparatus uses the third parameter as the second parameter.

5. A cryptographic communication system with a common key algorithm for communication between a transmitter apparatus and a receiver apparatus having a same cipher key, the transmitter apparatus encrypting a plain text by using the cipher key to acquire and transmit a cipher text, and the receiving apparatus decrypting the received cipher text by using the cipher key to recover the plain text, wherein:

said transmitter apparatus includes key length storing means for storing a key length data, first key sharing means for sharing a key data, and encrypting conversion means for encrypting;

said receiver apparatus includes second key sharing means for sharing a key data and decrypting conversion means for decrypting; and

prior to starting cryptographic communication, said transmitter and receiver apparatuses share the cipher key having a length designated by key length data stored in said key length storing means of said transmitter apparatus, by using said first key sharing means of said transmitter apparatus and said second key sharing means of said receiver apparatus.

6. A cryptographic communication system according to claim 5, wherein said transmitter apparatus uses predetermined specific key length data.

7. A cryptographic communication system according to claim 5, wherein:

said encrypting conversion means includes a plurality stage of a first substitution/permutation conversion means for performing substitution/permutation conversion and outputs the cipher text by processing the plain text at each of said first substitution/permutation conversion means by using the cipher key or data converted from the cipher key; and

each of said first substitution/permutation conversion means for data conversion includes bit train converters which include a plurality stage of cyclic shift operation means and a plurality stage of addition operation units.

8. A cryptographic communication system according to claim 7, wherein an output of each of said cyclic shift operation units is determined by input data to be converted and a portion of the third parameter.

9. A cryptographic communication system according to claim 7, wherein an output of each of said addition operation units is determined by input data to be converted and a portion of the third parameter.

10. A cryptographic communication system according to claim 5, wherein:

said decrypting conversion means includes a plurality stage of second substitution/permutation conversion means for performing substitution/permutation conversion and outputs the plain text by processing the cipher text at each of said second substitution/permutation conversion means by using the cipher key or data converted from the cipher key; and

each of said second substitution/permutation conversion means for data conversion includes bit train converters which include a plurality stage of cyclic shift operation means and a plurality stage of addition operation means.

11. An IC card to be used for an electronic toll collection system capable of collecting a toll from the IC card inserted into an on-board apparatus of a car running on a toll road, while the car passes by a road side equipment on the toll road, without stopping the car, said on-board apparatus including encrypting/decrypting conversion means for encrypting and decrypting a data and first algorithm key storing means for storing an algorithm key, and a conversion algorithm to be performed by the encrypting/decrypting conversion means of the on-board apparatus being determined by a first parameter stored in the first algorithm key storing means, wherein:

the IC card comprises said encrypting/decrypting conversion means and second algorithm key storing means for storing an algorithm key;

a conversion algorithm to be performed by said encrypting/decrypting conversion means of the IC card is determined by a second parameter stored in the second algorithm key storing means of the IC card; and

the IC card can cryptographically communicate with the on-board apparatus only if the second parameter is same as the first parameter.

12. An on-board apparatus to be used for an electronic toll collection system capable of collecting a toll from an IC card inserted into the on-board apparatus of a car running on a toll road, while the car passes by a road side equipment on the toll road, without stopping the car, the on-board apparatus including encrypting/decrypting conversion means and first algorithm key storing means, and a conversion algorithm to be executed by the encrypting/decrypting conversion means of the on-board apparatus being determined by a first parameter stored in the first algorithm key storing means, wherein:

the on-board apparatus comprises said encrypting/decrypting conversion means and second algorithm key storing means;

a conversion algorithm to be executed by said encrypting/decrypting conversion means of the on-board apparatus is determined by a second parameter stored in the second algorithm key storing means of the on-board apparatus; and

the on-board apparatus can cryptographically communicate with the road side apparatus only if the second parameter is same as the first parameter.

13. A road side apparatus to be used for an electronic toll collection system capable of collecting a toll from an IC card inserted into an on-board apparatus of a car running on a toll road, while the car passes by the road side equipment on the toll road, without stopping the car, the on-board apparatus including encrypting/decrypting conversion means and first algorithm key storing means, and a conversion algorithm to be executed by the encrypting/decrypting conversion means of the on-board apparatus being determined by a first parameter stored in the first algorithm key storing means, wherein:

the road side apparatus comprises said encrypting/decrypting conversion means and second algorithm key storing means;

a conversion algorithm to be executed by said encrypting/decrypting conversion means of the road side apparatus is determined by a second parameter stored in the second algorithm key storing means of the road side apparatus; and

the road side apparatus can cryptographically communicate with the on-board apparatus only if the second parameter is same as the first parameter.

14. An encrypting conversion apparatus for inputting at least one cipher key and plain text data and outputting cipher text data, the encrypting conversion apparatus comprising:

a plurality stage of encrypting conversion means for performing a substitution conversion for substituting data for different data and a permutation conversion for rearranging bits of data,

wherein said encrypting conversion means executes either an exclusive logical sum operation or an addition operation of input data and first data generated from the cipher key, thereafter executes the substitution and permutation conversions, thereafter executes either an exclusive logical sum operation or an addition operation of the input data and second data generated from the cipher key, and thereafter executes the substitution conversion.

15. A decrypting conversion apparatus for inputting at least one cipher key and cipher text data and outputting plain text data, the decrypting conversion apparatus comprising:

a plurality stage of decrypting conversion means for performing a substitution conversion for substituting data for different data and a permutation conversion for rearranging bits of data,

wherein said decrypting conversion means executes either an exclusive logical sum operation or an addition operation of input data and first data generated from the cipher key, thereafter executes the substitution and permutation conversions, thereafter executes either an exclusive logical sum operation or an addition operation of the input data and second data generated from the cipher key, and thereafter executes the substitution conversion.

16. An encrypting method for inputting at least one cipher key, at least one algorithm parameter, and plain text data and outputting cipher text data, said encrypting method comprising the steps of:

performing a plurality stage of encryptions each by executing each of an exclusive logical sum operation, a cyclic shift operation and an addition operation at least once,

said encrypting step including at least one of each of first to third operation sub-steps, said first operation sub-step, executing either an exclusive logical sum operation or an addition operation of input data and a portion of data generated from data of the cipher key, said second operation sub-step executing either an exclusive logical sum operation or an addition operation of input data and a portion of data determined by the algorithm parameter, and said third operation sub-step cyclically shifting input data by the number of bits determined by the algorithm parameter; and

combining a plurality stage of consecutive encrypting steps optionally selected from all of said encrypting steps with use of the same input data and the same algorithm parameter such that the encryption results are all different.

17. A decrypting method for inputting at least one cipher key, at least one algorithm parameter, and cipher text data and outputting plain text data, said method comprising the steps of:

performing a plurality stage of decryptions each by executing each of an exclusive logical sum operation, a cyclic shift operation and an addition operation at least once,

said decrypting step including at least one of each of first to third operation sub-steps, said first operation sub-step executing either an exclusive logical sum operation or an addition operation of input data and a portion of data generated from data of the cipher key, said second operation sub-step executing either an exclusive logical sum operation or an addition operation of input data and a portion of data determined by the algorithm parameter, and said third operation sub-step cyclically shifting input data by the number of bits determined by the algorithm parameter; and

combining a plurality stage of consecutive decrypting steps optionally selected from all of said decrypting steps with use of the same input data and the same algorithm parameter such that the decryption results are all different.