A Technical Seminar on

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• Anonymizing Peer-to-Peer(P2P) systems is essential to mask the identities of the users for the privacy consideration.

• They are mainly of 2 types─ Path based─ Non-path based

• Rumor Riding is an example for non-path –based mutual anonymity protocol for decentralized P2P systems.

• RR uses the symmetric cryptographic algorithms.

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• Fully utilizes the resource of the whole system.

• Peers are both clients and servers in an overlay network.

• There are mainly 2 types of P2P systemsStructured P2P systemsUnstructured P2P systems

• In structured P2P networks, peers are organized following specific criteria and algorithms, which lead to overlays with specific topologies and properties.

• Unstructured P2P networks do not impose any structure on the overlay networks.

• Unstructured P2P systems are of 3 types:CentralizedDecentralizedHybrid

• Anonymity is the state of being indistinguishable from other members of some group.

• In terms of the computer community, the anonymity requirement is especially important for those users who want to protect their personal, private, and sensitive information, such as the user name, ID, and IP address, during communication with others.

• Not trying to protect content of message.

• Anonymity can be

─ Path-based─ Non-path-based

• Anonymous paths has to be pre-constructed.

• Uses RSA algorithm.

• Both the peer collection and content encryption introduce high costs.

• No need to collect public keys for pre-construct a “secured path”.

• Changing delivery paths often.

• Eliminating path maintenance overhead.

• Used AES cryptographic algorithm.

• Reduce cryptographic overhead for the Initiator, Responder and Middle nodes

• Rumor Riding is a lightweight and non-path-based mutual anonymity protocol for P2P systems.

• Rumor Riding includes five major components:

1. Rumor Generation and Recovery.2. Query Issuance.3. Query Response.4. Query Confirm.5. File Delivery.

1. Rumor Generation and Recovery

Initiator I

Cipher rumor Key rumor

sower sa

Flooding

Responder

Initiator I

Responder

Response key rumor

Reversed Path of key rumor

Response cipher rumor

sower sb

TCP Link

sower sa

Reversed path of cipher rumor

IPsa

IPsbRe

Initiator I

Responder

Reversed path of responsekey rumor

Reversed path of response cipher rumor

sower sb

Confirm cipher rumor

Confirm key rumor

sower sc

TCP Link

Initiator I

Responder

Data rumor Data rumor

sower sd

TCP Link

sower sc

Multiple Rumor Riding

•In RR, an initiator can issue multiple rumors in the query cycle. This scheme is denoted as (i, j)-RR, which issues i cipher rumors and j key rumors.

•Advantage of the multiple rumors is that RR can be more reliable as more sowers can serve the query.

Rumor TTL

•The adaptive TTL determination of RR has two phases: (a) setting initial TTL value. (b) adaptively adjusting TTL.

Rumor Cache

•Storage overhead is related to the speed of query generation.Ex: Each peer normally issues no more than 0.3 queries per minute on average.

•FIFO schemes are used to handle cache overflow.

1. Sower Distribution and Collision Rate

• P2P systems mainly utilize three communication patterns to deliver messages: flooding, random walk, and end-to-end delivery.

• Collision distance may be defined as the number of hops present in the shortest path between the initiator and the sower.

• If this collision distance is sufficiently large then receivers are randomly distributed in the network.

1. Anonymity model

a) Anonymity setb) Mutual information system

2. Attacks

•Suppose network has m adversary nodes then probability of peer being an adversary is m/n.

Collaborating attack Withstands attacks

Timing attack Withstands attacks

Traceback attack Withstands attack

Predecessor attack Withstands attacks

Traffic analysis attack

Withstands attacks

Collaborating attack versus RR. (a) Collaborating attack.(b) Selective flooding of sowers.

Collaborating attack

1.Collision rateTo verify the theoretical results . we examine the distribution

of collision rate with real traces. Besides the verification, we also use the results to guide the selection of rumor parameters.

2.Collision distanceA longer collision distance often means a higher anonymity

level, but also increases the delay of a query as well as the traffic overhead. On the other hand, the collision distance must be sufficiently large to guarantee sower diversity.

3.Sower diversityThe metric reflects the distribution of sower locations in the

P2P systems. Evenly random distribution of sower location leads to a higher anonymity degree.

4.Number of sowersSince each sower implements a selective flooding search for an

initiator, too many sowers will incur a large number of replicated query messages, and too few sowers will result in failure on providing enough redundancy and reliability.

5.Traffic overheadThe amount of traffic overhead represents the comprehensive

latency in data delivery and bandwidth

6.Response timeIn P2P systems, it is defined as the time elapsed from when a

query is issued to when the first response arrives.

7.Crypto latencyThe overhead incurred by the main cryptographic algorithms

• Employing a random walk concept, RR issues key rumors and cipher rumors separately, and expects that they meet in some random peers.

• Various attacks defended by RR is also considered.

• This protocol can be even extended in other distributed systems, such as grid systems and ad-hoc networks.

REFERENCES[1] Rumor Riding: Anonymizing Unstructured Peer-to-Peer Systems Yunhao Liu, Senior Member, IEEE, Jinsong Han, Member, IEEE, and Jilong Wang, Member, IEEE, VOL. 22, NO. 3, MARCH 2011.

[2] Low-Cost and Reliable Mutual Anonymity Protocols in Peer-to-Peer Networks Li Xiao, Member, IEEE, ZhichenXu, Member, IEEE, and Xiaodong Zhang, Senior Member, IEEE, VOL. 14, NO. 9, SEPTEMBER 2003.

[3] Rumor Riding: A Protocol for Providing Anonymity Harish A, Veerapandian N International Journal of Soft Computing and Engineering (IJSCE) ISSN: 2231-2307, Volume-1, Issue-ETIC2011, January 2012.

[4] JOURNAL OF COMPUTER SCIENCE AND TECHNOLOGY 23(4): 660{671 July 2008 Survey on Anonymity in Unstructured Peer-to-Peer Systems Ren-Yi Xiao.

[5] http://en.wikipedia.org/wiki/Peer-to-peer.

Thank you…

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