1. UbiBay An auction system for mobile multihop ad-hoc networks * Hannes Frey, Johannes K. Lehnert, Peter Sturm System Software and Distributed Systems, University of Trier * This work is funded in part by DFG, Schwerpunktprogramm SPP1140 “Basissoftware für selbstorganisierende Infrastrukturen für vernetzte mobile Systeme”

2. Assumptions Metropolitan sized networking Mobile devices  Wireless communication facilities Direct communication only within communication range Unpredictable topology changes due to mobility  Network partitions  Permanent link failures

3. The UbiBay application People sell low-value goods “in their neighborhood”  Too much effort to put it on eBay  Enough potential buyers locally  Need for “cheap” communication Exchange of goods  By appointment  Supermarkets etc. as trustworthy third parties  Quick auctions at popular places: people have goods with them Auctions of low-value goods well suited for ad-hoc networks  Decentralized and self-organizing  Restricted geographical area  Not time-critical

4. The UbiBay application Start new auctions  Describe auction  Define minimum bid and duration See a list of all known auctions  View details: bids, duration, description Participate in auctions  Define maximum bid Notifications  of being outbid  of finished auctions UbiBay Auctions running: Bidding on: Auctioneer for: 10 CD-RsJ. Doe$5.5 Details Bid TitleAuctioneerBid TitleAuctioneerBidMax Dilbert bookS. Smith$7$10 Bid Dilbert bookS. Smith$7 Details Bid Title#BidsLeaderBid Calendar3B. Stevens$1.5

5. The UbiBay application Devices communicate through messages  Auction/Description/Notification message  Dissemination of messages with PeriodiCast UbiBay application on all mobile devices  Redistributes received messages  Distributed maximum computation  Handles bidding up to maximum bid  Protects maximum bid

6. The UbiBay application Reputation system  Buyer and seller rate each other  Differentiate personal and community ratings  Use counters to measure reliability  Disseminate ratings using PeriodiCast  Follows approach by Schneider et. al., 2000 Security  Ensure integrity of messages  Cope with replay and suppression of messages  Decentralized and self-organizing CA

7. PeriodiCast Use device discovery for background information dissemination  Fill unused parts of MTU  Distribute information over several discovery messages  Handle fragmentation  Timeouts avoid collisions/congestion Applications reserve buffers/ports  Guaranteed priority  Notification after dissemination Allows parallel use of other communication patterns unused Device discovery MTU ID Port ID Port ID Port priority based scheduling Application 1Application 2 buffer

8. Enhancements/Future work Handle message suppression  Observing mechanism: neighbors detect malicious devices Allow mobility of auction agents  Marketplace communication pattern Position-based routing  Protect the maximum bid through secret sharing Implement UbiBay on real hardware  Field test with students