1. 1 P2P Reputation Management Using Distributed Identities and Decentralized Recommendation Chains Authors: P. Dewan and P. Dasgupta Source: IEEE Transactions on Knowledge and Data Engineering, vol. 22, no. 7, pp. 1000- 1013, 2010 Speaker: Shu-Fen Chiou ( 邱淑芬 )

2. 2 Outline Introduction Proposed method Experimental results Conclusions Comments

3. 3 De-centralized P2P Architecture 1 2 3 4 5 6 7 8 Query abc.mp3 abc.mp3 REC: 0.3 REC: -0.5 REC: 0.6REC: 0.65

4. 4 Problem 8 8’8’ 8’8’ 8’8’ 8’8’ 8’8’ False transaction REC=0.3-> 0.8 1 2 3 4 5 6 7 8 Query abc.mp3 abc.mp3 REC: 0.8 REC: -0.5 REC: 0.6 REC: 0.3 liar farms

5. 5 Contributions A self-certification-based identity system protected by cryptographically blind identity mechanisms. A light weight and simple reputation model. An attack resistant cryptographic protocol for generation of authentic global reputation information of a peer.

6. 6 Proposed method P CA Request certificate Search file or service Get list and decide the provider with the highest reputation Verify, get file or service, and feedback reputation (Recommend)

7. 7 Proposed method Peer (P) Authority (A) B1, I Alice B2 P K1, P K2 A K1, A K2 B1={EB Ka (I Aliceτ )} B2=E A K2 {EB Ka (I Aliceτ )} E A K2 {I Aliceτ }={EB Ka {B2}} Certification request

8. 8 Proposed method Requester (R) Provider (P) RTS, IDR IDP, TID, E P K2 (H(TID||RTS)) P K1, P K2 Search for network: Search(P K1 ||TID) LTID=Max(Search(PK1||TID)) Check LTID<TID Past Recommendation Request, r CHAIN, E P K2 (CHAIN) Verify CHAIN file or service B1 B1=EB Ka (REC||TID||E R K2 {H(REC||TID)}) R K1, R K2 B1||E P K2 (H(B1),nonce), nonce Ka verify Decrypt B1 Stores: (IDR, {REC||TID||E R K2 {H(REC||TID)}})

9. 9 Experimental Results

10. 10 Experimental Results

11. 11 Conclusions Presents self-certification, an identity management mechanism, reputation model, and a cryptographic protocol. The self-certification-based identity generation mechanism reduces the threat of liar farms.