METHOD FOR PRESERVING PRIVACY OF A REPUTATION INQUIRY IN A PEER-TO-PEER COMMUNICATION ENVIRONMENT

• US 20090136033A1
• Filed: 11/28/2008
• Published: 05/28/2009
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Bon K. Sy
• Original Assignee: Bon K. Sy
• Inventors: Sy, Bon K.
• Granted Patent: US 8,498,415 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04L 2209/42 Anonymization, e.g. involving pseudonyms
• CPC Class Codes: H04L 2209/50 Oblivious transfer
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/76 Proxy, i.e. using intermediary entity to perform cryptographic operations network architectures or network communication protocols using hop-by-hop encryption H04L63/0464
• CPC Class Codes: H04L 9/008 involving homomorphic encryption

Abstract

A method for preserving privacy of a reputation inquiry in a peer-to-peer communication environment. The method allows peers using their own personal agents to obtain reputation information of each other through a pair of trustworthy mediator proxies. A mediator proxy is considered trustworthy if even when it is compromised it can guarantee three conditions: (1) the anonymity of the identity of the responders and the target being inquired; (2) the privacy of the content in an inquiry and a response; and (3) the boundary limit of the reputation summary with no possibility of combining the response of multiple inquiries to reverse engineer the reputation rating of an individual responder.

Claims

1. A method for preserving privacy of a reputation inquiry in a peer-to-peer communication environment with an inquiry handler, a response handler, a plurality of parties including at least one responder, an inquirer, an inquiry target, wherein the responder has a rating score that rates the inquiry target, the method comprising the steps of:

generating an inquiry vector about the inquiry target, wherein the inquiry vector has a plurality of elements and the generating step is performed by the inquirer;

applying homomorphic encryption, by the inquirer, to each element of the inquiry vector and specifying a corresponding encryption key, thereby producing an encrypted inquiry, wherein the encryption key is known by the inquirer and is not known by the inquiry handler, the response handler, the inquiry target or the responder;

sending the encrypted inquiry to the inquiry handler;

broadcasting the encrypted inquiry to the responder, wherein the broadcasting step is performed by the inquiry handler,

identifying the response handler to the responder such that each responder can send a response to the response handler, the step of identifying the response handler being performed by the inquiry handler;

responding by raising each element of the encrypted inquiry vector by a power equal to the rating score, thereby generating a response to the inquiry, wherein the raising step is performed by the responder;

transmitting the responses from the responder to the response handler;

producing a summary response, wherein the step of producing is performed by the response handler;

sending the summary response from the response handler to the inquirer; and

decrypting the encrypted summary response using the encryption key.

2. The method of claim 1, wherein the inquiry vector is algebraically constructed from a linear combination of at least two queries.

3. The method of claim 2, further comprising the step of finalizing the summary response by adding a random noise from a random number generator with a seed value and the seed value is sent to the inquirer along with the summary response.

4. The method of claim 3, further comprising the step of composing the linear combination of the response vectors to reconstruct the response vector to the original inquiry;

and wherein said composing step occurs directly after said decryption step.

5. A method for preserving privacy of a reputation inquiry in a peer-to-peer communication environment with an inquiry handler, a response handler, a plurality of parties including at least one responder, an inquirer, an inquiry target, wherein the responder has a rating score that rates the inquiry target, the method comprising the steps of:

specifying an agent to act on behalf of the inquirer;

generating an inquiry vector about the inquiry target, wherein the inquiry vector has a plurality of elements and the generating step is performed by the agent;

applying homomorphic encryption, by the agent, to each element of the inquiry vector and specifying a corresponding encryption key, thereby producing an encrypted inquiry, wherein the encryption key is known by the agent and is not known by the inquiry handler, the response handler, the inquiry target or the responder;

sending the encrypted inquiry to the inquiry handler;

broadcasting the encrypted inquiry to the responder, wherein the broadcasting step is performed by the inquiry handler,

identifying the response handler to the responder such that each responder can send a response to the response handler, the step of identifying the response handler being performed by the inquiry handler;

responding by raising each element of the encrypted inquiry vector by a power equal to the rating score, thereby generating a response to the inquiry, wherein the raising step is performed by the responder;

transmitting the response from the responder to the response handler;

producing a summary response, wherein the step of producing is performed by the response handler;

sending the summary response from the response handler to the agent;

decrypting the encrypted summary response using the encryption key.

6. The method of claim 5, wherein the inquiry vector is algebraically constructed, by the agent, from a linear combination of at least two queries.

7. The method of claim 5, wherein the agent chooses the encryption key.

8. The method of claim 5, wherein the step of sending the encrypted inquiry includes sending, by the agent, each element one-by-one to the inquiry handler.

9. The method of claim 8, wherein there are at least two responders and said responding step includes generating, by each responder, a response by raising each element of each at least one encrypted inquiry vector to a power of the rating score for the respective responder.

10. The method of claim 9, farther comprising the step of finalizing the summary response by adding a random noise from a random number generator with a seed value and the seed value is sent to the inquirer along with the summary response.

11. The method of claim 9, wherein the step of sending the summary response to the agent includes sending, by the response handler, the summary response to the agent using the identifying information provided by the inquiry handler.

12. The method of claim 5, wherein the step of decrypting the encrypted summary response is performed by the agent.

13. The method of claim 5, wherein the step of algebraic construction is performed by the agent.

14. The method of claim 5, wherein the summary response includes only a single element.

15. The method of claim 5, wherein after the step of decrypting the encrypted summary response, the decrypted summary response is sent to the inquirer.

16. The method of claim 15, wherein the step of sending the decrypted summary response from the agent to the inquirer includes a one-out-of-n oblivious transfer between the agent and inquirer.