Time stamping system

• US 20050125672A1
• Filed: 09/10/2002
• Published: 06/09/2005
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Ncipher Security Limited
• Original Assignee: nCipher Corporation Limited (Thales SA)
• Inventors: Harvey, Ian Nigel
• Granted Patent: US 7,650,508 B2
• Time in Patent Office: Days
• US Class Current: 713/178
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

A secure time stamping device uses multiple virtual clocks, each of which may be individually accessed and calibrated. A digital key is associated with each of the clocks. All of the virtual clocks use a common timer (130), with the actual clock output being generated by applying calibration information (124) for that clock to the timer (130) output. A user wishing to have a message time stamped presents that message along with information as to which virtual clock to be used at a device input (92). The appropriate calibration information (124) is then selected and the timer (130) output is compensated accordingly. The incoming message plus the resultant time are concatenated and automatically signed using the key (126) applicable to that particular virtual clock.

Claims

1. A time-stamping device for digitally time-stamping input data, comprising:

(a) a timer having a timer output;

(b) memory means for storing a plurality of sets of timer calibration information, each defining characteristics of a respective virtual clock;

(c) compensation means for adjusting the timer output in accordance with a user-selected virtual clock, to generate a selected virtual clock output; and

(d) signature means for generating a time-stamped output in dependence upon the selected virtual clock output and the input data.

2. The time-stamping device as claimed in claim 1 in which each virtual clock has associated with it a respective signature key, the signature means generating the time-stamped output using the key associated with the selected virtual clock.

3. The time-stamping device as claimed in claim 2 in which the signature means concatenates the selected virtual clock output and the input data, and signs the resultant concatenated data.

4. The time-stamping device as claimed in claim 2 in which each signature key comprises a private part of a public/private key pair

5. The time-stamping device as claimed in claim 2 including key access control means for authorizing requests for key management operations.

6. The time-stamping device as claimed in claim 1 including time-stamp access control means for authorizing user requests to time-stamp the input data in accordance with a given virtual clock output.

7. The time-stamping device as claimed in claim 1 including virtual clock access control means for authorizing requests to modify the calibration information for a given virtual clock.

8. The time-stamping device as claimed in claim 1 in which the timer is a free-running timer.

9. The time-stamping device as claimed in claim 1 in which the timer receives timing signals from an external source.

10. The time-stamping device as claimed in claim 1 comprising a hardware module.

11. A time-stamping device for digitally time-stamping input data, comprising:

(a) a plurality of user-selectable clocks, each having a signature key associated with it; and

(b) signature means for generating a time-stamped output in dependence upon an output of a user-selected clock and the input data.

12. A method of digitally time-stamping input data, comprising:

(a) selecting one set of timer calibration information from a plurality of such sets, each set defining the characteristics of a respective virtual clock;

(b) adjusting a timer output in accordance with the selected set to generate a selected virtual clock output; and

(c) signing data representative of both the selected virtual clock output and the input data to generate a time-stamped output.

13. The method as claimed in claim 12 in which each virtual clock has associated with it a respective signature key, the method including generating the time-stamped output using the key associated with the selected virtual clock.

14. The method as claimed in claim 13 including concatenating the selected virtual clock output and the input data, and signing the resultant concatenated data.

15. The method as claimed in claim 13 in which each signature key comprises a private part of a public/private key pair.

16. The method as claimed in claim 13 including checking the credentials of requests for key management operations.

17. The method as claimed in claim 12 including checking credentials of user requests to time stamp the input data in accordance with a given virtual clock output.

18. The method as claimed in claim 12 including checking the credentials of requests to modify the calibration information for a given virtual clock.

19. A method of digitally time-stamping input data, comprising:

(a) selecting one of a plurality of user-selectable clocks, each having a signature key associated with it; and

(b) generating a time-stamped output by signing data representative of an output of the selected clock and the input data.