Efficient and secure data currentness systems

• US 20040237031A1
• Filed: 05/13/2004
• Published: 11/25/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Assa Abloy AB
• Original Assignee: Corestreet, Ltd. (Assa Abloy AB)
• Inventors: Volbright, Brandon, Libin, Phil, Micali, Silvio
• Granted Patent: US 7,657,751 B2
• Time in Patent Office: Days
• US Class Current: 715/511
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3265 using certificate chains, trees or paths; Hierarchical trust model

Abstract

Indicating data currentness includes, on any date of a sequence of dates, issuing a proof indicating the currentness status of the data during a particular time interval. The proof may be a digital signature. The time interval may be in the form of a current date and an amount of time. The proof may include a digital signature of the time interval. The proof may include a digital signature of the time interval and the data. The proof may include a digital signature of the time interval and a compact form of the data, such as a hash. Indicating data currentness may also include distributing the proofs to a plurality of unsecure units that respond to requests by users for the proofs. Indicating data currentness may also include gathering a plurality of separate pieces of data and providing a single proof for the separate pieces of data. The data may be electronic documents.

Claims

1. A method of conveying currentness information about a document that is one of a plurality of documents, comprising:

at every date j of a sequence of dates, and for every document i of the plurality of documents, having a currentness authority compute individual currentness status information Ci about i by digitally signing information identifying i, date j and an indication whether i continues to be valid, or is obsolete, or is suspended;

providing the digitally signed currentness status information Ci to a responder;

for each document i in a plurality of documents, having the responder store the latest received Ci; and

in response to an inquiry about currentness status of document i, having the responder provide the latest received Ci.

2. A method, according to claim 1, wherein digitally signing includes digitally signing with respect to a public verification key pk, which is digitally signed by the document authority with respect to another public verification key PK.

3. A method, according to claim 2, wherein the public verification key pk, is contained as part of the document i.

4. A method, according to claim 1, wherein the currentness status information Ci of an obsolete document i includes a signature indicating that i has been revoked together with i'"'"'s revocation date.

5. A method, according to claim 1, wherein the currentness status information Ci of an obsolete document i includes a signature indicating a more current version of the document.

6. A method, according to claim 1, wherein the responder is not trusted and can not make an obsolete or suspend document current and cannot make a current document obsolete or suspended.

7. A method, according to claim 1, wherein information identifying i is i itself

8. A method, according to claim 1, wherein information identifying i is a compact representation of i.

9. A method, according to claim 8, wherein the compact representation is computed via a hash function.

11. A method, according to claim 1, wherein information identifying i is a serial number.

12. A method, according to claim 1, wherein the currentness authority receives updates of document currentness from the document authority and uses them in order to compute the currentness status of documents

13. A method, according to claim 12, wherein the currentness authority computes the status of each document as valid until the updates inform otherwise.

14. A method, according to claim 12, wherein the currentness authority computes the status of each document as valid until a prespecified date and time.

15. A method, according to claim 1, wherein each date in the sequence of dates is determined by the document authority.

16. A method, according to claim 1, wherein the document i contains information on the currentness authority responsible for updating the currentness status.

17. A method, according to claim 3, wherein the currentness authority produces the public key pk and makes it available to the document authority, while retaining the corresponding secret key sk.

18. A method, according to claim 1, wherein the currentness authority is the same entity as document authority.

19. A method of conveying currentness information about a document that is one of a plurality of documents, comprising:

at every date j of a sequence of dates, and for every document i of the plurality of documents, computing individual currentness status information Ci about i by digitally signing information identifying i, date j and an indication whether i continues to be valid, or is obsolete, or is suspended;

for each document i in a plurality of documents, storing the latest Ci; and

in response to an inquiry about currentness status of document i, providing the latest received Ci.

20. A method of verifying whether a particular document that is one of a plurality of documents is currently valid at a current date, comprising:

receiving particular currentness status information about the particular document, wherein currentness status information Ci, for every document i is determined by having a currentness authority compute individual Ci about document i by digitally signing information identifying i, date j for every date j of a sequence of dates, and an indication whether i continues to be valid, or is obsolete, or is suspended; and

confirming that the particular currentness status information was digitally signed by the currentness authority and that the particular currentness status information indicates that the particular document continues to be valid at the current date.