1/19 DIANE Project Philipp Obreiter, Birgitta König-Ries, Michael Klein Stimulating Cooperative Behavior of Autonomous Devices An Analysis of Requirements and Existing Approaches Universität Karlsruhe Institute for Program Structures und Data Organization Universität Karlsruhe GERMANY The Second International Workshop on Wireless Information Systems April 2003 – Angers, France

2/19 Absence of Infrastructure

3/19 Autonomy Autonomous devices devices are free to cooperate or not Sound assumption tampered devices re-engineered protocol stacks absence of an enforcing authority Devices tend to be uncooperative scarceness of resources (e.g. battery power)  cooperative behavior must be stimulated

4/19 Overview Cooperation and uncooperative behavior Issues for Incentive Schemes Existing Incentive Schemes

5/19 Conceptual Layering Application Discovery Transport Network Link User Interface Application Discovery Transport Network Link User Interface device Adevice B autonomy border

6/19 Elementary Cooperation PrincipalAgent action remuneration service ConsumerProvider check Application Layer forwarding SenderRouter reputation Network Layer

7/19 Taxonomy of Uncooperative Behavior lavish behaviorselfish behavior by agentby principal malicious behavior unprofitableprofitable profitable misbehavior misbehaviorvenial noncooperation reasonableunreasonable uncooperative behavior

8/19 Exemplification of Uncooperative Behavior Application Discovery Transport Network Link User Interface Application Discovery Transport Network Link User Interface Dropping packets under heavy load  venial noncooperation Application Network Transport Discovery DoS attack  malicious behavior Drop other devices' advertisements  selfish behavior Wastefully consume other devices' services  lavish behavior

9/19 Incentive Schemes Incentive Scheme set of mechanisms that restrict misbehavior exempt venial noncooperation from punishment Current approaches for Ad Hoc Networks TermiNodes Sprite APE RPG Watchdog/Pathrater CONFIDANT CORE

10/19 Issues for Incentive Schemes Trust Transactions Remuneration types

11/19 Incentive Scheme Issues: (1) Trust Trust prerequisite for remuneration mechanisms an incentive for cooperation Static Trust certification of an entity's trustworthiness requires cryptographic infrastructure Dynamic Trust arises from prior experiences need for reputation management considers behavioral change

12/19 Incentive Scheme Issues: (2) Transactions Transaction encompasses elementary cooperation agent executes action iff principal remunerates agent Negotiation phase agreement on the action and remuneration determined by the respective cost/profit ratios Processing phase assertion of atomicity seems daunting approximated atomicity by interleaving action and remuneration efficient low value transactions by aggregating actions and remunerations

13/19 Incentive Scheme Issues: (3) Remuneration Remuneration type different types have been proposed most popular types checks, e.g., TermiNodes reputation, e.g., Marti et al 2000 Transferability passing on checks disseminating reputation Convertibility cashing checks reconciling user and device views of reputation

14/19 Account Based Incentive Schemes: Properties Remuneration mechanism every entity possesses an account accounts stored on virtual banks principal issues a check agent accesses a virtual bank in order to credit its account Implementation requires static trust mechanisms virtual banks managed by dedicated devices banker nodes accessibility? accounts distributed to account holders tamper resistant hardware

15/19 Classification (1) Approach Properties Termi- Nodes SpriteAPE Scope Coop. domainN/T N Selfishnessyes Lavishnessyes Maliciousnessyes- Remuneration typechecks Transferability/ Dissemination yes-- Convertibility-yes Sniffing--- Truststatic Implemen- tation Tamper resistance security modules -- Cryptographic infrastructure public key Trans- action Negotiationyes- Processingaction/remuneration Flex. remunerationyes

16/19 Reputation Based Incentive Schemes: Properties Remuneration mechanism principal adapts agent's reputation according to its action agent might decrease principal's reputation agent only cooperative if principal has good reputation Implementation couple trust and remuneration local views of reputation may be kept local shared, i.e., disseminated increases effectiveness introduces further opportunities for misbehavior requires stable or localized cooperation patterns

17/19 Classification (2) Approach Properties Termi- Nodes SpriteAPERPG Watchdog / Pathrater CON- FIDANT CORE Scope Coop. domainN/T NNNNN Selfishnessyes - Lavishnessyes ---- Maliciousnessyes- - - Remuneration typechecksreputation Transferability/ Dissemination yes--- only positive Convertibility-yes ---- Sniffing----yes Truststaticdynamic Implemen- tation Tamper resistance security modules Cryptographic infrastructure public key ---- Trans- action Negotiationyes Processingaction/remuneration Flex. remunerationyes ----

18/19 Conclusion Summary cooperation beyond autonomy borders requires stimulation cooperation of protocol entities on different layers taxonomy and exemplification of uncooperative behavior discussion of incentive schemes trust transactions remuneration classification of existing approaches for ad hoc networks account vs. reputation based Future work incentive scheme for the discovery and application layer analysis of suitable remuneration types integration of incentive schemes

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20/19 Matching Remuneration Types to Layers