Simple efficient mutual anonymity protocols for peer-to-peer network based on primitive roots

1. Simple efficient mutual anonymity protocols forpeer-to-peer network based on primitive roots Source: Journal of Network and Computer Applications, vol. 30, pp. 662-676, 2007. Authors: Chin-Chen Chang, Chih-Yang Lin, and Keng-Chu Lin Speaker: Shu-Fen Chiou (邱淑芬)

2. Outline • Introduction • Xiao et al.’s protocols • Proposed method • Conclusion

3. Introduction • A Peer can act three roles • Publisher • Requester • Provider (Responder) Pub 1.mp3 Req Pro

4. Introduction • Hybrid P2P File list Requester P2 P0 TTP 1.mp3 P1 P3 P1 provider

5. Introduction • Pure P2P Requester P2 1.mp3 P0 P5 P3 P5 provider P5 P1 1.mp3 Download file

6. Xiao et al.’s protocols • Mix-based hybrid P2P protocol 1. Generate symmetric secret key 2. Select m peers for cover path, encrypt with their public key provider

7. Xiao et al.’s protocols cont. • Pure P2P protocol provider shortcut

8. Xiao et al.’s protocols cont. • Disadvantage • Scalability • TTP know the details of providers and requesters.

9. Primitive roots {1,3,7,9} 2 is a primitive root

10. Hybrid P2P mutual anonymity • System initialization • Address (alias) of gij mod p, j=1~p-1 • p=7, gi=3 U2, TTP, U3, U1, U4, TTP 6 4 5 1 31 mod 7=3 32 mod 7=2 gi=5 5 4 6 2 3 1 TTP,U1,U4 TTP,U3,TTP Sub-path address table U2 TTP

11. Hybrid P2P mutual anonymity • Peer initialization Randomly selects one path {{FLi}KT,Ni} Ni+1 Ui Ni+2 … TTP Construct an index database

12. Hybrid P2P mutual anonymity provider

13. Shortcut-responding protocol provider Random probability pj>pi->shortcut node

14. Pure P2P mutual anonymity p=5, p-2=3 peers involved Random select p-1 number x1, x2,.., xp-1 Peer gets gj generates alias gjxi

15. Anonymity analysis TTP TTP . . . • Total n peers • Between two consecutive aliases of TTP • sn: smallest numbers of peers • ln: largest number of peers • TTP: guess requester -> 1/sn guess provider -> 1/n-ln

16. Anonymity analysis • Requester (or provider): 1/(n-1) • Middle node: guess R or P -> 1/(n-1) if know number of middle nodes k guess R or P -> 1/(n-k) • Local eavesdropper: guess R or P -> 1/(n-1) • Cooperating peers: if k cooperating peers guess R or P -> 1/(n-1)

17. Conclusions • The covert paths can be dynamically generated. • It is guaranteed that all the peers and the TTP can pass any of the covert paths. • Different primitive roots generate different covert paths, which raises the level of flexibility and anonymity of the protocol.

18. Comments TTP {NTTP, file_id, true, K} {Ni, file_id, null, K} Ui 1.Generate symmetric keys Nm {Ni, file_id, true, K} Nq {Nn, file_id, true, {f}K} {Nj, file_id, true, {f}K} Uj

19. Comments • Pure P2P • Initiator generates peers’ aliases and transmits them to peers.