Electric equipment, and method and program for preventing unauthorized use of same

• US 20040044903A1
• Filed: 08/07/2003
• Published: 03/04/2004
• Est. Priority Date: 08/08/2002
• Status: Active Grant

• Current Assignee: NEC Display Solutions, Ltd. (NEC Corporation)
• Original Assignee: NEC Viewtechnology, Ltd. (NEC Corporation)
• Inventors: Komatsu, Yoshiharu
• Granted Patent: US 7,512,992 B2
• Time in Patent Office: Days
• US Class Current: 713/200
• CPC Class Codes: G06F 21/30 Authentication, i.e. establishing the identity or authorisation of security principals
• CPC Class Codes: G06F 21/62 Protecting access to data via a platform, e.g. using keys or access control rules
• CPC Class Codes: G06F 21/70 Protecting specific internal or peripheral components, in which the protection of a component leads to protection of the entire computer
• CPC Class Codes: G06F 21/88 Detecting or preventing theft or loss
• CPC Class Codes: G06F 2221/2153 Using hardware token as a secondary aspect

Abstract

Electric equipment, and a method and a program for preventing the unauthorized use of same, by which it is possible to prevent the theft of electric equipment installed in an environment where the electric equipment is available for the use of an unspecified number of users and the stealing of information stored in the electric equipment. The electric equipment comprises: an operation limiting section for setting a function limit to make at least part of functions of the electric equipment unavailable; an I/F for connecting an external device to the electric equipment; an external device information obtaining section for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device; a write control section for associating the function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key; an NVRAM for storing the cryptographic key; and a comparator for determining whether or not the device identification information obtained from an external device connected via the interface to the electric equipment matches the cryptographic key stored in the NVRAM. The operation limiting section cancels the function limit when the comparator determines that the obtained information matches the cryptographic key.

Claims

1. Electric equipment comprising:

a function limiting section for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

an interface for connecting an external device to the electric equipment;

a section for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a section for associating the function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key;

a memory for storing the cryptographic key;

a determining section for determining whether or not the device identification information obtained from an external device connected via the interface to the electric equipment matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling section for canceling the function limit set by the function limiting section when the determining section determines that the obtained information matches the cryptographic key.

7. The electric equipment claimed in claim 1, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

13. The electric equipment claimed in claim 1, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

19. The electric equipment claimed in claim 1, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

2. Electric equipment comprising:

a function limiting section for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

an interface for connecting an external device to the electric equipment;

a section for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a section for associating each function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key;

a memory for storing the cryptographic key;

a determining section for determining whether or not the device identification information obtained from an external device connected via the interface to the electric equipment matches the device identification information included in the cryptographic key stored in the memory; and

a limit canceling section for canceling each function limit set by the function limiting section when the determining section determines that the obtained information matches the device identification information associated with the function limit.

8. The electric equipment claimed in claim 2, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

14. The electric equipment claimed in claim 2, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

20. The electric equipment claimed in claim 2, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

3. Electric equipment comprising:

a function limiting section for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a plurality of interfaces for connecting external devices to the electric equipment;

a section for obtaining device identification information from an external device connected via one of the interfaces to the electric equipment to identify the device;

a section for associating the function limit with the specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a memory for storing the cryptographic key;

a determining section for determining whether or not the device identification information obtained from each external device connected via one of the interfaces to the electric equipment matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling section for canceling the function limit set by the function limiting section when the determining section determines that the obtained information matches the cryptographic key.

9. The electric equipment claimed in claim 3, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

15. The electric equipment claimed in claim 3, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

21. The electric equipment claimed in claim 3, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

4. Electric equipment comprising:

a function limiting section for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a plurality of interfaces for connecting external devices to the electric equipment;

a section for obtaining device identification information from an external device connected via one of the interfaces to the electric equipment to identify the device;

a section for generating connection route information indicating which interface is used to connect the external device that has provided the device identification information;

a section for associating the function limit with a combination of prescribed device identification information and relevant connection route information to thereby obtain a cryptographic key;

a memory for storing at least one cryptographic key;

a determining section for determining whether or not a combination of the device identification information obtained from each external device connected via one of the interfaces to the electric equipment and the connection route information for the external device matches the combination of the device identification information and the connection route information of the cryptographic key stored in the memory; and

a limit canceling section for canceling the function limit set by the function limiting section when the determining section determines that the combination of the obtained information and connection route information matches the cryptographic key.

10. The electric equipment claimed in claim 4, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

16. The electric equipment claimed in claim 4, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

22. The electric equipment claimed in claim 4, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

5. Electric equipment comprising:

a function limiting section for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a plurality of interfaces for connecting external devices to the electric equipment;

a section for obtaining device identification information from an external device connected via one of the interfaces to the electric equipment to identify the device;

a section for associating each function limit with the specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a memory for storing at least one cryptographic key;

a determining section for determining whether or not the device identification information obtained from each external device connected via one of the interfaces to the electric equipment matches the device identification information of any one of the cryptographic keys stored in the memory; and

a limit canceling section for canceling each function limit set by the function limiting section when the determining section determines that the obtained information matches the device identification information of the cryptographic key related to the function limit.

11. The electric equipment claimed in claim 5, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

17. The electric equipment claimed in claim 5, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

23. The electric equipment claimed in claim 5, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

6. Electric equipment comprising:

a function limiting section for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a plurality of interfaces for connecting external devices to the electric equipment;

a section for obtaining device identification information from an external device connected via one of the interfaces to the electric equipment to identify the device;

a section for generating connection route information indicating which interface is used to connect the external device that has provided the device identification information;

a section for associating each function limit with a combination of prescribed device identification information and relevant connection route information to thereby obtain a cryptographic key;

a memory for storing at least one cryptographic key;

a determining section for determining whether or not a combination of the device identification information obtained from each external device connected via one of the interfaces to the electric equipment and the connection route information for the external device matches any one of the cryptographic keys stored in the memory; and

a limit canceling section for canceling each function limit set by the function limiting section when the determining section determines that the combination of the obtained information and connection route information matches the cryptographic key related to the function limit.

12. The electric equipment claimed in claim 6, further comprising a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information.

18. The electric equipment claimed in claim 6, further comprising a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

24. The electric equipment claimed in claim 6, further comprising:

a section for having the external device store information that uniquely identifies the external device as the device identification information when the external device is capable of storing information; and

a section for resetting the function limit when a prescribed period of time has passed after the determining section made a determination.

25. A method for preventing the unauthorized use of electric equipment including an interface to connect an external device thereto, comprising:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a step for associating the function limit with the device identification information obtained at the first device identification information obtaining step to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the cryptographic key.

31. The method for preventing the unauthorized use of electric equipment claimed in claim 25, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

37. The method for preventing the unauthorized use of electric equipment claimed in claim 25, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

43. The method for preventing the unauthorized use of electric equipment claimed in claim 25, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

26. A method for preventing the unauthorized use of electric equipment including an interface to connect an external device thereto, comprising:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a step for associating each function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information obtained at the second device identification information obtaining step matches the device identification information included in the cryptographic key stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key related to the function limit.

32. The method for preventing the unauthorized use of electric equipment claimed in claim 26, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

38. The method for preventing the unauthorized use of electric equipment claimed in claim 26, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

44. The method for preventing the unauthorized use of electric equipment claimed in claim 26, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

27. A method for preventing the unauthorized use of electric equipment including a plurality of interfaces to connect external devices thereto, comprising:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a step for associating the function limit with the specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information or a combination of plural pieces of device identification information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the cryptographic key.

33. The method for preventing the unauthorized use of electric equipment claimed in claim 27, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

39. The method for preventing the unauthorized use of electric equipment claimed in claim 27, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

45. The method for preventing the unauthorized use of electric equipment claimed in claim 27, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

28. A method for preventing the unauthorized use of electric equipment including a plurality of interfaces to connect external devices thereto, comprising:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a first connection route information generating step for generating first connection route information indicating which interface is used to connect the external device to the electric equipment at the first device identification information obtaining step;

a step for associating the function limit with a combination of prescribed device identification information and relevant connection route information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a second connection route information generating step for generating second connection route information indicating which interface is used to connect the external device to the electric equipment at the second device identification information obtaining step;

a determining step for determining whether or not a combination of the device identification information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the combination of the information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key.

34. The method for preventing the unauthorized use of electric equipment claimed in claim 28, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

40. The method for preventing the unauthorized use of electric equipment claimed in claim 28, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

46. The method for preventing the unauthorized use of electric equipment claimed in claim 28, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

29. A method for preventing the unauthorized use of electric equipment including a plurality of interfaces to connect external devices thereto, comprising:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a step for associating each function limit with the specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information or a combination of plural pieces of device identification information obtained at the second device identification information obtaining step matches the device identification information of any one of the cryptographic keys stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key related to the function limit.

35. The method for preventing the unauthorized use of electric equipment claimed in claim 29, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

41. The method for preventing the unauthorized use of electric equipment claimed in claim 29, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

47. The method for preventing the unauthorized use of electric equipment claimed in claim 29, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

30. A method for preventing the unauthorized use of electric equipment including a plurality of interfaces to connect external devices thereto, comprising:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a first connection route information generating step for generating first connection route information indicating which interface is used to connect the external device to the electric equipment at the first device identification information obtaining step;

a step for associating the function limit with a combination of prescribed device identification information and the first connection route information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a second connection route information generating step for generating second connection route information indicating which interface is used to connect the external device to the electric equipment at the second device identification information obtaining step;

a determining step for determining whether or not a combination of the device identification information obtained at the second device identification information obtaining step and the second connection route information matches any one of the cryptographic keys stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the combination of the information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key related to the function limit.

36. The method for preventing the unauthorized use of electric equipment claimed in claim 30, further comprising a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

42. The method for preventing the unauthorized use of electric equipment claimed in claim 30, further comprising a step for resetting the function limit when a prescribed period of time has passed after the determining step.

48. The method for preventing the unauthorized use of electric equipment claimed in claim 30, further comprising:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

49. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including an interface to connect an external device thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a step for associating the function limit with the device identification information obtained at the first device identification information obtaining step to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the cryptographic key.

55. The program for preventing the unauthorized use of electric equipment claimed in claim 49, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

61. The program for preventing the unauthorized use of electric equipment claimed in claim 49, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

67. The program for preventing the unauthorized use of electric equipment claimed in claim 49, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

50. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including an interface to connect an external device thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a step for associating each function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information obtained at the second device identification information obtaining step matches the device identification information included in any one of the cryptographic keys stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key related to the function limit.

56. The program for preventing the unauthorized use of electric equipment claimed in claim 50, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

62. The program for preventing the unauthorized use of electric equipment claimed in claim 50, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

68. The program for preventing the unauthorized use of electric equipment claimed in claim 50, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

51. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including a plurality of interfaces to connect external devices thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a step for associating the function limit with specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information or a combination of plural pieces of device identification information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the cryptographic key.

57. The program for preventing the unauthorized use of electric equipment claimed in claim 51, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

63. The program for preventing the unauthorized use of electric equipment claimed in claim 51, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

69. The program for preventing the unauthorized use of electric equipment claimed in claim 51, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

52. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including a plurality of interfaces to connect external devices thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting a function limit to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a first connection route information generating step for generating first connection route information indicating which interface is used to connect the external device to the electric equipment at the first device identification information obtaining step;

a step for associating the function limit with a combination of prescribed device identification information and relevant connection route information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a second connection route information generating step for generating second connection route information indicating which interface is used to connect the external device to the electric equipment at the second device identification information obtaining step;

a determining step for determining whether or not a combination of the device identification information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key stored in the memory; and

a limit canceling step for canceling the function limit set at the function limiting step when it is determined at the determining step that the combination of the information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key.

58. The program for preventing the unauthorized use of electric equipment claimed in claim 52, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

64. The program for preventing the unauthorized use of electric equipment claimed in claim 52, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

70. The program for preventing the unauthorized use of electric equipment claimed in claim 52, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

53. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including a plurality of interfaces to connect external devices thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a step for associating each function limit with the specific device identification information or a combination of plural pieces of specific device identification information to thereby obtain a cryptographic key;

a step for storing the cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a determining step for determining whether or not the device identification information or a combination of plural pieces of device identification information obtained at the second device identification information obtaining step matches the device identification information of any one of the cryptographic keys stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the information obtained at the second device identification information obtaining step matches the device identification information of the cryptographic key related to the function limit.

59. The program for preventing the unauthorized use of electric equipment claimed in claim 53, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

65. The program for preventing the unauthorized use of electric equipment claimed in claim 53, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

71. The program for preventing the unauthorized use of electric equipment claimed in claim 53, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.

54. A program for preventing the unauthorized use of electric equipment, which is built into the electric equipment including a plurality of interfaces to connect external devices thereto and makes a computer having effective control over the electric equipment execute steps as follows:

a function limiting step for setting one or more function limits to the electric equipment so that at least part of functions of the electric equipment becomes unavailable;

a first device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a first connection route information generating step for generating first connection route information indicating which interface is used to connect the external device to the electric equipment at the first device identification information obtaining step;

a step for associating the function limit with a combination of prescribed device identification information and the first connection route information to thereby obtain a cryptographic key;

a step for storing at least one cryptographic key in a memory;

a second device identification information obtaining step for obtaining device identification information from each external device connected via one of the interfaces to the electric equipment to identify the device;

a second connection route information generating step for generating second connection route information indicating which interface is used to connect the external device to the electric equipment at the second device identification information obtaining step;

a determining step for determining whether or not a combination of the device identification information obtained at the second device identification information obtaining step and the second connection route information matches any one of the cryptographic keys stored in the memory; and

a limit canceling step for canceling each function limit set at the function limiting step when it is determined at the determining step that the combination of the information obtained at the second device identification information obtaining step and the second connection route information matches the cryptographic key related to the function limit.

60. The program for preventing the unauthorized use of electric equipment claimed in claim 54, making the computer having effective control over the electric equipment execute a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information.

66. The program for preventing the unauthorized use of electric equipment claimed in claim 54, making the computer having effective control over the electric equipment execute a step for resetting the function limit when a prescribed period of time has passed after the determining step.

72. The program for preventing the unauthorized use of electric equipment claimed in claim 54, making the computer having effective control over the electric equipment execute further steps as follows:

a step for having the external device store information that uniquely identifies the external device as the device identification information after the first device identification information obtaining step when the external device connected to the electric equipment at the first device identification information obtaining step is capable of storing information; and

a step for resetting the function limit when a prescribed period of time has passed after the determining step.