Generating and verifying trusted digital time stamp

• US 20080288779A1
• Filed: 05/20/2008
• Published: 11/20/2008
• Est. Priority Date: 01/13/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Shao, Ling, Zhang, Jian, Xie, Dong
• Granted Patent: US 7,890,765 B2
• Time in Patent Office: Days
• US Class Current: 713/178
• CPC Class Codes: G06F 21/645 using a third party
• CPC Class Codes: G06F 21/725 operating on a secure reference time value
• CPC Class Codes: G06F 2221/2151 Time stamp
• CPC Class Codes: H04L 63/12 Applying verification of the received information cryptographic mechanisms or cryptographic arrangements for data integrity or data verification H04L9/32

Abstract

Methods, apparatus and systems for generating a trusted digital time stamp as well as a public time source. It includes, an apparatus for receiving and recording public time information and a method for verifying a digital time stamp. A method for generating a trusted digital time stamp includes: obtaining a first time information and a corresponding random code from a public time source; and generating a digital time stamp using a first time information and random code. A method for verifying a digital time stamp includes: recording time information and corresponding random codes transmitted by a public time source; retrieving time information and a random code contained in the time stamp; and comparing a retrieved random code from the time stamp with one of the recorded random codes that corresponds to a time information in the time stamp, if they are consistent, the time stamp is determined to be trusted, otherwise the time stamp is determined to be not trusted.

Claims

1. A method for generating a trusted digital time stamp, comprising:

obtaining first time information and a corresponding random code from a public time source; and

generating a digital time stamp using said first time information and random code.

2. The method for generating a trusted digital time stamp according to claim 1, wherein said step of generating a digital time stamp comprises:

calculating a digest based on data desired to be attached with a time stamp;

attaching said first time information and said random code to said digest; and

appending a digital signature.

3. The method for generating a trusted digital time stamp according to claim 1, wherein said step of generating a digital time stamp comprises:

calculating a digest based on data desired to be attached with a time stamp;

attaching said first time information and said random code to said digest and requesting a time stamp server to generate a server digital time stamp for it; and

generating the server digital time stamp by said time stamp server.

4. The method for generating a trusted digital time stamp according to claim 3, wherein said step of generating a digital time stamp further comprises:

receiving the digital time stamp generated by said time stamp server; and

locally appending a digital signature to the digital time stamp generated by said time stamp server.

5. The method for generating a trusted digital time stamp according to claim 3, wherein said step of generating a digital time stamp by said time stamp server, comprises:

attaching second time information representing the time when said request is received by said time stamp server; and

appending said time stamp server'"'"'s digital signature.

6. The method for generating a trusted digital time stamp according to claim 1, wherein said random code is a randomly generated real random number.

21. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing generation of a trusted digital time stamp, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer to effect the steps of claim 1.

22. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for generating a trusted digital time stamp, said method steps comprising the steps of claim 1.

29. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for verifying a digital time stamp, said method steps comprising the steps of claim 1.

7. A method for generating a trusted digital time stamp, comprising:

calculating a digest based on data desired to be attached with a time stamp;

obtaining a first time information and a corresponding random code from a public time source;

attaching said first time information and said random code to said digest; and

appending a digital signature.

23. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing generation of a trusted digital time stamp, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer to effect the steps of claim 7.

24. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for generating a trusted digital time stamp, said method steps comprising the steps of claim 7.

8. An apparatus for generating a local trusted digital time stamp, comprising:

a time information receiver for receiving time information and corresponding random code from a public time source; and

a local time stamp generation unit for generating a digital time stamp using said time information and said random code obtained by said time information receiver.

9. The apparatus for generating a local trusted digital time stamp according to claim 8, wherein the local time stamp generation unit comprises:

a digest calculation unit for calculating a digest based on data desired to be attached with a time stamp; and

a digital signature synthesizing unit for combining said digest calculated by said digest calculation unit and said time information and said random code received by said time information receiver and appending a digital signature.

10. The apparatus for generating a local trusted digital time stamp according to claim 8, wherein said apparatus further comprises:

a communication unit for communicating with a time stamp server, sending a request to said time stamp server for time stamp service and receiving a response from said time stamp server.

11. The apparatus for generating a local trusted digital time stamp according to claim 10, wherein said digital signature synthesizing unit further appending a digital signature to the time stamp coming from said time stamp server.

12. The apparatus for generating a local trusted digital time stamp according to claim 8, wherein said apparatus further comprises:

a time information buffer for temporarily storing the time information and corresponding random code received from said public time source.

16. The apparatus for generating a local trusted digital time stamp according to claim 8, included in a system comprising the public time source, the public time source to continuously provide time information representing current time and corresponding random codes, the public time source comprising:

a clock;

a random code generator for continuously generating random codes; and

a time information transmission means for transmitting the time information of said clock'"'"'s current time and the random code newly generated by said random code generator.

17. The apparatus for generating a trusted digital time stamp according to claim 16, wherein the system further comprises a time stamp server.

25. A computer program product comprising a computer usable medium having computer readable program code means embodied therein for causing generation of a trusted digital time stamp, the computer readable program code means in said computer program product comprising computer readable program code means for causing a computer to effect the functions of claim 8.

27. A computer program product comprising a computer usable medium having computer readable program code means embodied therein for causing generation of a trusted digital time stamp, the computer readable program code means in said computer program product comprising computer readable program code means for causing a computer to effect the functions of claim 16.

13. A public time source to continuously provide time information representing current time and corresponding random codes, comprising:

a clock;

a random code generator for continuously generating random codes; and

a time information transmission means for transmitting the time information of said clock'"'"'s current time and the random code newly generated by said random code generator.

14. A public time source according to claim 13, wherein said random code generator is a real random number generator.

26. A computer program product comprising a computer usable medium having computer readable program code means embodied therein for causing functions of a public time source, the computer readable program code means in said computer program product comprising computer readable program code means for causing a computer to effect the functions of claim 13.

15. A apparatus for receiving and recording public time information, to continuously receive and record time information and corresponding random codes coming from a public time source, comprising:

a time information receiving means for receiving said time information and corresponding random codes from said public time source; and

a time information recording means for recording said received time information and random codes.

18. A method for verifying a digital time stamp, comprising:

recording time information and corresponding random codes transmitted by a public time source;

retrieving time information and a random code contained in the time stamp; and

comparing said retrieved random code from the time stamp with one of the recorded random codes that corresponds to said time information in the time stamp, if they are consistent, the time stamp is determined to be trusted, otherwise the time stamp is determined to be not trusted.

19. The method for verifying a digital time stamp according to claim 18, wherein said time stamp further includes a local digital signature;

said method further comprises;

checking whether the local digital signature of the time stamp is legal or not, and determining that the time stamp is not trusted if the local digital signature of said time stamp is not legal.

20. The method for verifying a digital time stamp according to claim 18, wherein said time stamp further includes a time stamp server'"'"'s digital signature;

said method further comprises;

checking whether said time stamp server'"'"'s digital signature is legal or not, and determining that the time stamp is not trusted if said time stamp server'"'"'s digital signature is not legal.

28. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing verification of a digital time stamp, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer to effect the steps of claim 18.