Time Authentication Device, Time Authentication Method, Computer Program, Recording Medium, Integrated Circuit, and Time Authentication System

• US 20080127279A1
• Filed: 07/13/2005
• Published: 05/29/2008
• Est. Priority Date: 07/15/2004
• Status: Active Grant

• Current Assignee: Sovereign Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Nakano, Toshihisa, Futa, Yuichi, Matsuzaki, Natsume, Yamauchi, Hiroki
• Granted Patent: US 7,979,731 B2
• Time in Patent Office: Days
• US Class Current: 725/80
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 2463/121 Timestamp
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

The present invention aims to provide a time authentication device for distinguishing clocks that show a time falling within the predetermined permissible range as compared with a time shown by the time authentication device. In a time authentication device embodied as a distribution device 11, a time-relation information storage unit 104 stores a playback-device-time measured by a clock unit 203 of a playback device 12, and also stores a distribution-device-time measured by a clock unit 103 when the playback-device-time is acquired. The time authentication unit 107 acquires from the playback device 12 a target time measured by the clock unit 203, and also acquires an authentication time measured by the clock unit when the target time is received. The time authentication unit 107 then calculates a first difference (=Authentication Time−Distribution-Device-Time), a second difference (=Target Time−Playback-Device-Time), an authentication difference (=First Difference−Second Difference). If the authentication difference is smaller than or equal to a predetermined threshold, the time authentication unit 107 judges that the clock unit 203 of the playback device 12 is valid.

Claims

1. A time authentication device for authenticating a target clock that measures a time and that is included in a target device, the time authentication device comprising:

a clock unit operable to a measure time;

a storage unit operable to store a first time measured by the target clock and a second time measured by the clock unit when the first time is acquired;

an acquiring unit operable to acquire a third time measured by the target clock and a fourth time measured by the clock unit when the third time is acquired;

a judging unit operable to judge, based on the first time to the fourth time, whether a difference between a time measured by the target clock and a time measured by the clock unit falls within a permissible range; and

an output unit operable to output an authentication result indicating that the target clock is valid if the difference is judged to fall within the permissible range, and that the target clock is invalid if the difference is judged to fall outside the permissible range.

2. The time authentication device according to claim 1, wherein

the judging unit is operable to judge whether a third difference is smaller than or equal to a threshold, the third difference being a difference between (a) a first difference between the fourth time and the second time and (b) a second difference between the third time and the first time, and

the output unit is operable to output an authentication result indicating that the target clock is valid if the third difference is judged to be smaller than or equal to the threshold and thus fall within the permissible range, and that the target clock is invalid if the third difference is judged to be larger than the threshold and thus fall outside the permissible range.

3. The time authentication device according to claim 1, wherein

the judging unit is operable to judge whether a third difference is smaller than or equal to a threshold, the third difference being a difference between (a) a first difference between the fourth time and the third time and (b) a second difference between the second time and the first time, and

the output unit is operable to output an authentication result indicating that the target clock is valid if the third difference is judged to be smaller than or equal to the threshold and thus fall within the permissible range, and that the target clock is invalid if the third difference is judged to be larger than the threshold and thus fall outside the permissible range.

4. The time authentication device according to claim 1, wherein

the storage unit is operable to store, as the second time, a time measured by the clock unit when the first time is acquired, and

the acquiring unit is operable to acquire, as the fourth time, a time measured by the clock unit when the third time is acquired.

5. The time authentication device according to claim 1, wherein

the storage unit is operable to store, as the second time, a time measured by the clock unit when a request for sending the first time is issued to the target device, and

the acquiring unit is operable to acquire, as the fourth time, a time measured by the clock unit when a request for sending the third time is issued to the target device.

6. The time authentication device according to claim 1, wherein

the target device is operable to receive from the time authentication device a request for sending a time, and sends to the time authentication device a time that is measured by the target clock when the request is received, and

the acquiring unit includes:

a monitoring subunit operable to monitor the time measured by the clock unit;

a request subunit operable, when the time measured by the clock unit reaches a time that is a predetermined time period after the second time, to issue to the target device a request for sending a time;

a response acquiring subunit operable to acquire the third time sent from the target device in response to the time send request; and

a time acquiring subunit operable to acquire, as the fourth time, a time measured by the clock unit when the third time is acquired.

7. The time authentication device according to claim 2, wherein

the threshold is “

0”

, and

the judging unit is operable to calculate the third difference by subtracting the second difference from the first difference and to judge whether the third difference is smaller than or equal to “

0”

.

8. The time authentication device according to claim 2, wherein

the threshold is a value calculated by multiplying the first difference by a predetermined ratio, and

the judging unit is operable to judge whether the third difference is smaller than or equal to the value calculated by multiplying the first difference by the predetermined ratio.

9. The time authentication device according to claim 1, wherein

the target device is operable to use a content on or before a usage expiry of the content based on the target clock,

the time authentication device further comprising:

a content storage unit operable to store a content having a usage expiry; and

a send unit operable to send the content and the usage expiry to the target device if the authentication result indicates that the target clock is valid.

10. The time authentication device according to claim 9, wherein

the sending unit is operable to send, instead of the usage expiry, an expiry calculated by subtracting a third difference from the usage expiry, and

the third difference is a difference between (a) a first difference between the fourth time and the second time and (b) a second difference between the third time and the first time.

11. The time authentication device according to claim 9, wherein

the sending unit is operable to send, instead of the usage expiry, an expiry calculated by the following expression:

the fourth time+(the usage expiry−

the fourth time)×

(a first difference/a second difference), and

the first difference is a difference between the fourth time and the second time, and

the second difference is a difference between the third time and the first time.

12. The time authentication device according to claim 1, wherein

the acquiring unit is operable to acquire, as the third time, a time measured when the target device requests to start playback of the content.

13. The time authentication device according to claim 1, wherein

the target device is operable to store a content and a usage expiry of the content, and to use the content if a current time measured by the target clock is on or before the usage expiry,

the time authentication device further comprising:

an instruction unit operable, if the authentication result indicates that the target clock is invalid, to instruct the target device to rewrite the usage expiry so that use of the content is no longer permitted.

14. A time authentication method for use by a time authentication device for authenticating a target clock that measures a time and that is included in a target device,

the time authentication device including:

a clock unit operable to a measure time; and

a storage unit operable to store a first time measured by the target clock and a second time measured by the clock unit when the first time is acquired,

the method comprising;

an acquiring step of acquiring a third time measured by the target clock and a fourth time measured by the clock unit when the third time is acquired;

a judging step of judging, based on the first time to the fourth time, whether a difference between a time measured by the target clock and a time measured by the clock unit falls within a permissible range; and

an output step of outputting an authentication result indicating that the target clock is valid if the difference is judged to fall within the permissible range, and that the target clock is invalid if the difference is judged to fall outside the permissible range.

15. A computer program for use by a time authentication device for authenticating a target clock that measures a time and that is included in a target device,

the time authentication device including:

a clock unit operable to a measure time; and

a storage unit operable to store a first time measured by the target clock and a second time measured by the clock unit when the first time is acquired,

the program comprising code operable to cause the time authentication device to perform;

an acquiring step of acquiring a third time measured by the target clock and a fourth time measured by the clock unit when the third time is acquired;

a judging step of judging, based on the first time to the fourth time, whether a difference between a time measured by the target clock and a time measured by the clock unit falls within a permissible range; and

an output step of outputting an authentication result indicating that the target clock is valid if the difference is judged to fall within the permissible range, and that the target clock is invalid if the difference is judged to fall outside the permissible range.

16. A computer-readable recording medium, comprising:

a computer program as defined in claim 15 stored thereon.

17. An integrated circuit for use by a time authentication device for authenticating a target clock that measures a time and that is included in a target device, the integrated circuit comprising:

a clock unit operable to a measure time;

a storage unit operable to store a first time measured by the target clock and a second time measured by the clock unit when the first time is acquired;

an acquiring unit operable to acquire a third time measured by the target clock and a fourth time measured by the clock unit when the third time is acquired;

a judging unit operable to judge, based on the first time to the fourth time, whether a difference between a time measured by the target clock and a time measured by the clock unit falls within a permissible range; and

an output unit operable to output an authentication result indicating that the target clock is valid if the difference is judged to fall within the permissible range, and that the target clock is invalid if the difference is judged to fall outside the permissible range.

18. A time authentication system composed of

a target device having a target clock operable to measure a time;

and

a time authentication device for authenticating the time measured by the target clock,

the time authentication device comprising;

a clock unit operable to a measure time;

a storage unit operable to store a first time measured by the target clock and a second time measured by the clock unit when the first time is acquired;

an acquiring unit operable to acquire a third time measured by the target clock and a fourth time measured by the clock unit when the third time is acquired;

a judging unit operable to judge, based on the first time to the fourth time, whether a difference between a time measured by the target clock and a time measured by the clock unit falls within a permissible range; and

an output unit operable to output an authentication result indicating that the target clock is valid if the difference is judged to fall within the permissible range, and that the target clock is invalid if the difference is judged to fall outside the permissible range.