Anonymity revocation

• US 20050268103A1
• Filed: 05/25/2005
• Published: 12/01/2005
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Camenisch, Jan
• Granted Patent: US 7,581,107 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: G06Q 30/04 Billing or invoicing
• CPC Class Codes: H04L 2209/42 Anonymization, e.g. involving pseudonyms
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 9/3234 involving additional secure or trusted devices, e.g. TPM, smartcard, USB or software token network architectures or network communication protocols for supporting authentication of entities using an additional device in a packet data network H04L63/0853
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Methods and systems for anonymity revocation, enabling a trusted entity to identify a user computer within an anonymous system. A system comprises an attester computer providing attestation value cert from a security module public key and an identifying value. The user computer having a module providing the module public key and a security module attestation value, the user computer providing a user public key, a user attestation-signature value derived from the attestation value cert, and an encryption computable under use of a trusted-entity public key and a module-generated-identifier value, the module-generated-identifier value relating to the identifying value; a verification computer verifying validity of received user attestation-signature value and the encryption; and a trusted entity having a trusted entity secret key, wherein the trusted entity is able to derive the module-generated-identifier value from the encryption, the module-generated-identifier value being usable to identify the user computer with the security module.

Claims

1. A method for enabling a trusted entity to identify a user computer with a security module within a system comprising further an attester computer and a verification computer, the method comprising at the user computer the steps of:

receiving from the attester computer an attestation value, the attestation value being derived from a security module public key and an identifying value;

deriving under use of the security module a user attestation-signature value from the attestation value;

computing an encryption by the user computer under use of a trusted-entity public key and a module-generated-identifier value, the module-generated-identifier value relating to the identifying value; and

providing the user attestation-signature value and the encryption to the verification computer for verification,

wherein the trusted entity having a trusted entity secret key is able to derive the module-generated-identifier value from the encryption, the module-generated-identifier value being usable to identify the user computer with the security module.

2. The method according to claim 1, wherein the step of deriving the user attestation-signature value further comprises the steps of

receiving from the security module the module-generated-identifier value, and

deriving the encryption and encryption random values from the module-generated-identifier value under the use of the trusted-entity public key.

3. The method according to claim 2, further comprising the steps of:

receiving from the security module a second module-generated-identifier value, and

deriving an encryption proof value and encryption proof random values from the second module-generated-identifier value under the use of the trusted-entity public key.

4. The method according to claim 3 further comprising the steps of:

deriving an intermediary user-attestation signature value from the encryption and the encryption proof value under use of a hash function,

providing the intermediate user attestation-signature value to the security module;

receiving from the security module a first part of the user attestation-signature value, and

calculating by the user computer further parts of the user attestation-signature value by using the received first part of the user attestation-signature value, the encryption random values, the encryption proof random values, the attester public key, and the trusted-entity public key.

10. A computer program element comprising program code for performing the method of claim 1 when said program is run on a computer.

11. A computer program product stored on a computer usable medium, comprising computer readable program code for causing a computer to perform the method according to claim 1.

13. The method according to claim 1, further comprising billing the user computer with the security module when the trusted entity derived the module-generated-identifier value from the encryption, wherein the derived module-generated-identifier value identifies the user computer with the security module.

16. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing enablement of a trusted entity to identify a user computer, 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.

5. A method for enabling a trusted entity to identify a user computer comprising further an attester computer and a verification computer, the method comprising at the trusted entity the steps of:

providing a trusted-entity public key;

receiving an encryption computed by the user computer under use of the trusted-entity public key, wherein the encryption comprises a module-generated-identifier value relating to an identifying value which together with a security module public key was used by the attester computer to generate an attestation value; and

deriving the module-generated-identifier value from the encryption by applying a trusted entity secret key, the derived module-generated-identifier value being usable to identify the user computer with the security module.

6. The method according to claim 5, further comprising the steps of:

sending the derived module-generated-identifier value to the attester computer, and

in response to the sent derived module-generated-identifier value receiving the related identifying value identifying the user computer with the security module.

17. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein for causing enablement of a trusted entity to identify a user computer, 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 5.

7. A method for verifying a user attestation-signature value by a verification computer within a system in which an identity of a user computer with a security module is identifiable by a trusted entity, the system comprising further, and an attester computer, the method comprising at the verification computer the steps of:

receiving the user attestation-signature value and an encryption for verification, the encryption having been computed by the user computer under use of a trusted-entity public key and a module-generated-identifier value that relates to an identifying value which together with a security module public key was used by the attester computer to generate an attestation value, wherein the user computer under use of the security module derived the user attestation-signature value from the attestation value, wherein the trusted entity having a trusted entity secret key is able to derive the module-generated-identifier value from the encryption, the derived module-generated-identifier value being usable to identify the user computer with the security module; and

verifying the validity of the received user attestation-signature value and the encryption.

8. Method according to claim 7, wherein the step of verifying further comprises

computing a first verification value by using the user attestation-signature value, the attester public key, the trusted-entity public key, the encryption, and a hash-function, and

checking whether or not the first verification value is comprised in the user attestation-signature value.

18. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for verifying a user attestation-signature value, said method steps comprising the steps of claim 7.

9. A method for enabling identification of a user computer with a security module by a trusted entity within a system comprising further an attester computer and a verification computer, the method comprising at the attester computer the steps of:

deriving an attestation value from a security module public key and an identifying value;

providing the attestation value to the user computer which under use of the security module is able to derive a user attestation-signature value from the attestation value and to compute an encryption under use of a trusted-entity public key and a module-generated-identifier value,

the module-generated-identifier value relating to the identifying value, the user attestation-signature value and the encryption being verifiable by the verification computer,

wherein the trusted entity having a trusted entity secret key is able to derive the module-generated-identifier value from the encryption, the module-generated-identifier value being usable to identify the user computer with the security module.

14. The method according to claim 9, further comprising billing the user computer with the security module for the provided attestation value that relates to a service.

15. The method according to claim 9, further comprising billing the trusted entity for providing upon request one identifying value.

19. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for enabling identification of a user computer, said method steps comprising the steps of claim 9.

12. A network for enabling identification a user computer by a trusted entity, comprising:

an attester computer that provides an attestation value from a security module public key and an identifying value;

the user computer having a security module that provides the module public key and a security module attestation value, the user computer providing

a user public key,

a user attestation-signature value derived from the attestation value, and

an encryption computable under use of a trusted-entity public key and a module-generated-identifier value, the module-generated-identifier value relating to the identifying value;

a verification computer for verifying the validity of the received user attestation-signature value and the encryption; and

a trusted entity having a trusted entity secret key, wherein the trusted entity is able to derive the module-generated-identifier value from the encryption, the module-generated-identifier value being usable to identify the user computer with the security module.

20. A computer program product comprising a computer usable medium having computer readable program code means embodied therein for causing functions of a network for enabling identification a user computer, 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 12.