Method for preserving privacy of a reputation inquiry in a peer-to-peer communication environment

• US 8,498,415 B2
• Filed: 11/28/2008
• Issued: 07/30/2013
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Bon K. Sy
• Original Assignee: Bon K. Sy
• Inventors: Sy, Bon K.
• Primary Examiner(s): Patel, Ashok
• Assistant Examiner(s): GRACIA, GARY S
• Application Number:
  US12/324,969
• Publication Number:
  US 20090136033A1
• Time in Patent Office: 1,705 Days
• Field of Search: 380/255, 713/165, 713/167
• 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 computer networking 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, the inquiry handler and the response handler being separate entities, thereby achieving a separation of duty between the inquiry handler and the response handler;

sending the encrypted inquiry, across a computer network, 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, across a computer network, 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 a decryption key;

wherein the step of responding responds by constructing a rating vector make ₁₃RV(R^Pi,i)=T_i×

R^Pi wherein R^Pi is a vector storing a rating score for each of the parties P_i, where T_i is a transformation matrix of size n²×

n for mapping R^Pi of size n×

1 to rating vector V^Pi of size n²×

1 with zero padding, and T_i^T =[Z<sub>n×

n(i−

1)</sub> I<sub>n×

n</sub> Z<sub>n×

n(n−

i)</sub>]is composed of a zero matrix of size n×

n(i−

1), an identity matrix of size n×

n, and another zero matrix of size n×

n(n−

i), and then applying a response function make_Response(V^Pi, IV^Pk)=Π

_j=1<sup>n×

n</sup>(k^mj)^vj, where vj is j^th entry in the V^Pi, and k^mj is the j^th entry in IV^Pk, to raise each element of the encrypted inquiry vector by the power equal to the rating score.

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

generating, by the inquirer, a first and second query vector about the inquiry target, with respective first and second elements, wherein the first query vector and the second query vector may be algebraically combined according to a predetermined algebraic operation to form an inquiry vector;

applying homomorphic encryption to each first element and each second element of the first and second query vector and specifying a corresponding first and second encryption key, thereby producing a first and second homomorphically encrypted inquiry, wherein the first and second encryption keys are known by the inquirer and are not known by the response handler, the inquiry target or the responder, the inquiry handler and the response handler being separate entities, thereby achieving a separation of duty between the inquiry handler and the response handler;

sending the first and second inquiry vectors across a computer network to the inquiry handler;

broadcasting the first and second homomorphically 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;

receiving, by the response handler, first and second responses from the responder which correspond to the first and second homomorphically encrypted inquiries, wherein the responder raised each element of the first and second homomorphically encrypted inquiry vector by a power equal to the rating score;

producing, by the response handler, a first summary response corresponding to the first responses and a second summary response corresponding to the second responses;

sending the first and second summary responses to the inquirer; and

algebraically combining the first and second summary responses, by the inquirer, according to the predetermined algebraic operation to enable the inquirer to determine the rating score for the inquiry target as determined by the responder.

3. The method as recited in claim 2, wherein the step of applying homomorphic encryption is performed by the inquirer.

4. The method as recited in claim 2, wherein the inquirer chooses the first encryption key.

5. The method as recited in claim 2, further comprising a step of finalizing the first 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 first summary response.

6. The method as recited in claim 2, further comprising a step of specifying an agent to act on behalf of the inquirer.

7. The method as recited in claim 6, wherein the step of applying homomorphic encryption is performed by the agent.

8. The method as recited in claim 7, wherein the step of sending the first and second inquiry vectors sends the first and second inquiry vectors from the agent to the inquiry handler.