wfwang@njupt.edu.cnwfwang@njupt.edu.cn or or wfwang@itslab.csce.kyushuwfwang@itslab.csce.kyushu--u.ac.jpu.ac.jp

Research on trust and incentive mechanismｓ in distributed systems

based on multi-disciplinary principles

Wang YufengInformation Technology & Security Laboratory, Kyushu University

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OutlineOutline

• Introduction to Chinese academic research • Research motivations • Current research state• Research contents• Multi-disciplinary concepts and solutions

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Introduction to myselfIntroduction to myself• Wang Yufeng, received Ph.D degree from State Key

Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunication, China, June, 2004.

• From July 2004 till June 2006, I acted as lecturer, in Nanjing University of Posts and Telecommunications.

• Presently, I act as PostDoc researcher under the supervision of Prof. SAKURAI.

• http://itslab.csce.kyushu-u.ac.jp/%7Ewfwang/index.html• Research interests: P2P, sensor networks, etc.

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Location of Location of NanjingNanjing

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Location of Location of NanjingNanjing citycity

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Security related research in ChinaSecurity related research in China

• Information Security Center (ISC) is the important part of this key lab. The present director of ISC is Prof. Yang YiXian, a very excellent young scientist in China, almost three hundred Ph.Dand master graduate student, postDoc researcher.

• http://www.bupt.edu.cn/yuanxi/introduce/jisuanji/nationalLab/• The main research fields: Networks Security; Security mobile

communications; Theory and applications of modern cryptography; Theory and applications of information hiding; Digital contents and its security; Applied security technology.etc.

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Security related research in China (cont.)Security related research in China (cont.)• The State Key Laboratory Of Information Security

(SKLOIS) http://www.is.ac.cn/, belongｓ to institute of software, Chinese academic of science.

• Research area: Cryptographic Theory and Technology; Security Protocols; Information Counterwork; Network and System Security

• As of July 2002, there were more than 120 researchers including visiting scholars, post-doctoral, doctoral, and masters students in SKLOIS.

• The 2nd SKLOIS Conference on Information Security and Cryptology ((Inscrypt, formerly CISC) , http://www.is.iscas.ac.cn/cisc/. Held in November 29 - December 1, 2006, Beijing, China,

• Deadline for Submission:July 15, 2006

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Other research fieldsOther research fields

• The general research fields includes: telecommunication, information technologies, computer science and technologies, electronic engineering, automatic control, optical technologies etc. the above fields are features of Beijing (Nanjing) university of Posts and Telecommunications.

• It is common to cooperate among those universities.

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Motivations and current stateMotivations and current state• Traditional system: participants behave

according to the intentions of the system architects.

• distributed networks like P2P, MANET, sensor network etc.: heterogeneous, dynamic and distributed environments

• managed by multiple administrative authorities and shared by users with different and competing interests.

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PeerPeer--toto--Peer SystemsPeer Systems• Distributed application

where nodes are:– Autonomous– Very loosely coupled– Equal in role or

functionality– Share and exchange

resources with each other• each individual

participator (peer) is self-interest (or rational)

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Quick Introduction to Classical Quick Introduction to Classical PrisonerPrisoner’’s Dilemmas Dilemma

Row Player A

Column Player BShare Not Share

3 3Reward for Mutual

Generosity0 5

5 01 1

Punishment for mutual

selfishness

Share

Not Share

Individual rationality leads to a worse outcome for both, than possible.

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SelfSelf--interest in distributed systemsinterest in distributed systems• Self-interest means that simply malicious or

faulty assumption, fail to address the challenges of rational behavior.

• Conclusion: respect peers’ rationality, and design proper incentive mechanisms to encourage peer to conduct something beneficial to the whole system, while peer pursued their own utility.

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IncentiveIncentive--compatible P2P topologycompatible P2P topology• much research on P2P topology construction

algorithms based on the peer capacity or semantic small-world model.

• ignored one fundamental problem: peers may lie about their private information to reduce the incurred overhead.

• In what interaction rules, direct revelation is peer’s first choice? And based on those interaction rule to construct P2P topology, incentive-compatible P2P topology.

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FreeridingFreeriding and whitewasherand whitewasher• P2P systems assumed two roles

simultaneously: communications infrastructure and social-economic entity.

• free-riding: contribute less to the system than they consume from it, or contribute nothing

• Whitewashing: because of anonymity, P2P system can not distinguish whitewasher from new comer.

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measurement of measurement of freeridingfreeriding• Free-riding problem

– Nearly 70% users do not share.• Tragedy of the Commons

– Nearly 50% request responses are from top 1% nodes.• Objective

– Provide Incentive to share information.– Provide Service Differentiation for users.– Provide mechanism to isolate malicious users.

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QoSQoS in distributed systemsin distributed systems• it is necessary to investigate how to

seamlessly integrate the incentive mechanisms into the QoS algorithms based on multi-discipline principles

• By QoS in P2P systems it not only means that traditional network-specific performance, but more important, application-specific performance as a whole, like reliability, availability and security etc.

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A

Trustworthy sensor communityTrustworthy sensor community

B• Although cryptography and authentication helps,

it alone is not sufficient for the unique characteristics and novel misbehaviors encountered in sensor networks.

• tools from different domains such as economics theory, statistics and data analysis will facilitate to form trustworthy community in sensor networks.

How can a user trust the information provided by the sensor network?

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Interesting applicationInteresting application-- P2P gaP2P gameme• P2P gaming is the most interesting P2P

application. But, the development of P2P games faces a significant obstacle: the issue of trust.

• In a game without trusted, centralized resources, how can competing parties ensure fairness on their own?

• it is viable to attempt to apply those research results in our proposal to P2P gaming research.

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Research contentsResearch contents

P2P Applications P2P gaming

P2P topology construction based on Incentive compatibility principle

Application Level Multicast

(ALM)

Instant Message (IM)

Peer semantic interest

Peer capacity …

QoS algorithms integrated with incentive mechanisms

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MultiMulti--disciplinary tools disciplinary tools • One clear need is to make use of the most of

research results of these different fields: mathematics, economics, information sciences, and social theory.

• Game theory, which try to understand how decision-makers interact, appears to be a natural tool for studying systems composed of autonomous entities.

• Three basic elements: player, strategy space, preference and payoff.

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MultiMulti--disciplinary Toolsdisciplinary Tools• Mechanism design: “Inverse game theory”,

given desired goals, design the game which will have the desired outcome in equilibrium when self-interested nodes pursue self-interested strategies.

• For example, if efficiency is the goal, then there is a general technique for constructing truthful mechanisms: Vickrey-Clarks-Groove (VCG) mechanism.

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Incentive compatibilityIncentive compatibility• we should respect rationality of peers, and design

proper incentive mechanisms to encourage peer to conduct something beneficial to the whole system, while peers pursued their own utility. That is incentive-compatible principle (incentive-compatibility).

• The key to overcoming the individual rationality of defection or free-riding is through encouraging reciprocity among the peers. Reciprocity can be facilitated through trust-based (reputation-based) or trade-based (token-based) approaches.

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illustration of elementary cooperationillustration of elementary cooperation

• Remuneration. In most incentive patterns, the principal entity remunerates the agent entity.– Type.– Granularity.– Assessment– Storage site

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A Taxonomy of Incentive Patterns• In trust based incentive patterns, the agent entity is stimulated

by the trust it has in the principal entity. Trust either accrues from membership (collective pattern) or it is subject to entities’behavior and, thus, adapts dynamically (community pattern). On contrary, in trade based incentive patterns, the agent entity isstimulated by an action in return that is either executed simultaneously (barter trade pattern) or promised (bond based incentive patterns).

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Features of incentive patternsFeatures of incentive patterns• The collective and community pattern seem to be too

restrictive with regard to their scalability and fuzzy accounting; easy to implement and can be combined with other patterns.

• Barter trade exhibits several features that are desirable :– anonymous: The participating entities do not have to disclose

their identity; – offline: Cooperation and remuneration do not require

interaction with specific third parties; – persistent: The remuneration is effective, even if the

participating entities are disconnected immediately after their cooperation.

– However, for most cooperation patterns, it is infeasible to execute a simultaneous action in return. Even so, the exchange is unlikely to be fair due to the actions’ granularity.

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Features of incentive patterns (cont.)Features of incentive patterns (cont.)

• The introduction of various bonds reduces the desirable characteristics of barter trade.

• Persistence: calls for a third party that is often accessible and provides the promised action in return. Furthermore, trust intensive roles are delegated to such a third party, in order to maintain anonymity of the principal and agent.

• Currently, the lack of a decentralized, scalable, low-overhead digital cash system hampers uptake of economic models.

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The importance of trustThe importance of trust

• Risks and threats in P2P– Gnutella Example– No trusted third parties

• Main security techniques without trusted third parties– Micropayments– Reputation based trust systems - building trust through

social control

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Trust Establishing MechanismsTrust Establishing Mechanisms

securitymechanisms

institutional

inte

rper

sonal

hierarchicalCA’s

P2P reputationmechanisms

reputationmechanisms

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Taxonomy of reputationTaxonomy of reputation

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Trust DefinitionsTrust Definitions[McKnight et al.]• Trusting belief is the extent to which a peer

believes that another peer is trustworthy in this situation.

• Trustworthy means one is willing and able to act in the other entity’s best interest.– Consistency, Willingness, Competency, and Honesty

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Reputation Systems Reputation Systems -- ChallengesChallenges• Effective trust model

– Accurately and Effectively capture the trustworthiness of peers– Ability to cope with malicious behaviors of peers– Ability to adapt to different communities and situations

• Implementation– Decentralized implementation– Secure implementation

• Experimental evaluation

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Reputation Mechanism DesignReputation Mechanism Design

ReputationMechanism

Trusting Agent

Trusted AgentMechanism Designer

Value of ReputationSemantics of Reputation &Protocol Implementation

Reputation Information &Reputation Reports

Reputation Information &Reputation Reports

RULES

Trust DecisionMaximize the gain of the Trusting Agent given the available data (i.e. the REPUTATION):

- scale the value of the transaction

- decide whether or not to trade

Reputation has a direct influence on future gains.

Value of R: How much more can a Trusted Agent gain by starting with reputation R?

Value for a negative or positive feedback report!

INCENTIVE COMPATIBLE

COLLUSION RESISTENCE

SCALABLE

RELIABLE

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Other research topicsOther research topics• P2P topology construction, considering several factors:

like peer locality in underlying infrastructure, peer semantic interest, peer capacity, etc.

• Generally, there exist two classes of P2P overlay networks: unstructured and structured. – Features of unstructured P2P: effective for locating highly replicated

items and are resilient to peers joining and leaving the system, but they are poorly suited for locating rare items, and not scalable

– Features of structured P2P: can efficiently locate rare items since the key-based routing is scalable, they incur significantly higher overheads than unstructured P2P networks for popular content, and they do not provide efficient fuzzy keyword based search (semantic-based search)

• the integration of the merits of unstructured and structured P2Pbased on the virtual region to maintain the tradeoff between maintenance cost and search cost.

• P2P application carried on the MANET: the cross-layer design principle, that is the interaction between P2P application layerand MANET network layer.

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Possible innovationsPossible innovations• This research adopts multidisciplinary principles

to design and evaluate incentive-compatible P2P topology formation and adaptation mechanism, incentive mechanisms used to solve or alleviate the impact of freerideing and whitewashing attack, and investigate the QoS in whole system, as the result of local interaction among peers.

• Base on the viewpoint that wireless sensor network can be regarded as specific P2P application carried on MANET, this research attempts to apply P2P distinguished features and incentive mechanisms to sensor network, and improve its efficiency.

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ConclusionConclusion