Management of certificates for public key infrastructure

• US 6,940,979 B1
• Filed: 11/09/2000
• Issued: 09/06/2005
• Est. Priority Date: 11/09/2000
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Bobbitt, Michael A.
• Primary Examiner(s): Barron, Jr., Gilberto
• Assistant Examiner(s): NALVEN, ANDREW L
• Application Number:
  US09/708,662
• Time in Patent Office: 1,762 Days
• Field of Search: 380/277, 713/175, 713/156, 713/158
• US Class Current: 380/277
• CPC Class Codes: H04L 9/006 involving public key infrastructure [PKI] trust models network architecture or network communication protocol for supporting authentication of entities using certificates in a packet data network H04L63/0823
• CPC Class Codes: H04L 9/3268 using certificate validation, registration, distribution or revocation, e.g. certificate revocation list [CRL]

Abstract

Management of ciphertext devaluation in public key infrastructure is addressed by providing system and method using a certificate having a validity dependent on the amount of ciphertext associated with the certificate, i.e. a ciphertext limited certificate (CLC). Thus when the amount of ciphertext reaches or exceeds a predetermined value, the certificate is invalid. The CCE may be expressed as a non critical extension to a X.509 certificate to allow for interoperability with conventional validity conditions based on validity period or revocation. Ciphertext limited certificates may be implemented in an X.509 standard environment based on a method of assigning and determining a certificate ciphertext entitlement (CCE), calculating a generated Ciphertext index (CGI) and performing a CCE threshold detection, and when the GCI reaches or exceeds the CCE, causing a key update, e.g. a rollover of the certificate. Assurance levels may be set based on assigning different CCE default values.

Claims

1. A certificate for Public Key Infrastructure (PKI), the certificate validity being determined by the amount of ciphertext associated with the certificate,

wherein when the amount of ciphertext generated is below a predetermined value, the

certificate is valid, and when the amount of ciphertext generated reaches a predetermined value, the certificate is invalid, comprising:

an extension including a Certificate Ciphertext Entitlement (CCE) value defining the amount of data that it is permissible for a certificate to encrypt before it must be rendered invalid;

an object identifier defining the units for ciphertext entitlement; and

an associated Ciphertext Generated Index (GCI) defining the count of how much cyphertext has been encrypted by the key,

the certificate validity also being dependent on the elapsed time and revocation status

wherein the certificate validity is defined by $\left(\mathrm{Certificate\_Validity}\right)=\frac{k}{\left(\mathrm{Ciphertext\_Generated}\right)+\left(\mathrm{Elapsed\_Time}\right)}\bigwedge <br><br>\left(\mathrm{Revocation\_Status}\right)$

wherein k is a constant value representing the assurance level of the keys in use.

2. A certificate according to claim 1 wherein the extension also defines a version of the Ciphertext limited certificates in effect for the certificate.

3. A certificate according to claim 1 wherein the CCE is expressed as a non-critical extension to a X.509 certificate.

4. A certificate according to claim 1 wherein the CCE included in the signed body of the certificate.

5. A certificate according to claim 3 wherein CCE default values are dependent on assurance level assigned to the certificate.

6. A certificate for a PKI system according to claim 1 compatible with the X.509 standard.

7. A method of managing ciphertext devaluation in a PKI, comprising:

determining a certificate ciphertext entitlement (CCE)

calculating a generated ciphertext index (GCI) wherein calculating the generated ciphertext index (GCI) comprises decrypting and verifying the decryption log

performing a certificate ciphertext entitlement threshold detection

and when the GCI reaches or exceeds the CCE causing a key update.

8. A method according to claim 7 wherein the key update is implemented as a rollover of the certificate or by invalidating the certificate.

9. A method according to claim 8 wherein the key update is implemented as an immediate rollover.

10. A method according to claim 8 wherein the key update is implemented at next log-in.

11. A method according to claim 7, comprising generating a time stamped decryption log.

12. A method according to claim 7 comprising,

when data is decrypted, checking for a unique identifier associated with each ciphertext archive that has been decrypted,

and if the unique identifier is found, the GCI is not updated

and when the unique identifier is not found in the decryption log, updating the decryption log and adding the size of the current decrypted data to the GCI.

13. A method according to claim 12 wherein the unique identifier is the hash of the symmetric key used to encrypt the data.

14. A method according to claim 13 wherein the decryption log is kept only for ciphertext archives that have been encrypted using the most current key pair.

15. A method according to claim 7 wherein the GCI is stored in bytes and the GCI is converted into units corresponding to the Certificate ciphertext Entitlement during threshold detection.

16. A method according to claim 7 wherein the decryption log and GCI are signed and encrypted by the certificate subject.

17. A method according to claim 7 wherein the GCI is contained in the decryption log.

18. A method according to claim 7 wherein the step of performing a certificate ciphertext entitlement threshold detection is performed each time decryption takes place.

19. A method according to claim 7 wherein the step of performing a certificate ciphertext entitlement threshold detection is performed at log in.

20. A method of managing ciphertext devaluation in a PKI, comprising:

determining a certificate ciphertext entitlement (CCE);

calculating a generated ciphertext index (GCI);

performing a certificate ciphertext entitlement threshold detection and

when the GCI reaches or exceeds the CCE, causing a key update,

wherein the step of performing a certificate ciphertext entitlement threshold detection comprises decrypting the GCI, verifying the digital signature, converting the GCI to units stipulated in the CCE extension, comparing the GCI to the CCE ad if GCI is greater than or equal to the CCE, requesting a key update in accordance with policy requirements.

21. A method according to claim 20 wherein after the key update has taken place, clearing the existing decryption log and GCI to reset the count.

22. A system for managing ciphertext devaluation in a PKI, comprising:

means for determining a certificate ciphertext entitlement (CCE)

means for calculating a generated ciphertext index (GCI)

means for performing a certificate ciphertext entitlement threshold detection comprising means for decrypting the GCI, verifying the digital signature, converting the GCI to units stipulated in the CCE extension, and comparing the GCI to the CCE

and means for causing a key update when the GCI reaches or exceeds the CCE.

23. A computer readable medium for implementing a method of managing ciphertext devaluation in a PKI, comprising:

determining a certificate ciphertext entitlement (CCE)

calculating a generated ciphertext index (GCI) and

performing a certificate ciphertext entitlement threshold detection comprising decrypting the GCI, verifying the digital signature, converting the GCI to units stipulated in the CCE extension, and comparing the GCI to the CCE

and, when the GCI reaches or exceeds the CCE, causing a key update.