Trusted Accounting in Peer-to-Peer Environments – A Novel Token-based Accounting Scheme for Autonomous Distributed Systems
Key: Lie08-1
Author: Nicolas Liebau
Date: December 2008
Kind: @phdthesis
Keywords: Peer-to-Peer, p2p, decentralised accounting, decentralised trustworthiness, decentralised cooperation control, Peer-to-Peer, P2P, dezentrales Accounting, dezentrale Vertrauenswürdigkeit, dezentrale Kooperationskontrolle
Abstract: Communication systems based on the peer-to-peer (p2p) paradigm present what is likely the most important development in Internet technology in recent years. In spite of the position of p2p systems as the largest source of traffic on the Internet, their commercial success is still limited. The basic tenets of p2p systems are cooperation among peers and completely decentralised communication. However, these can result in nontransparent actions, as well as opportunistic behaviour of the individual peers. Thus, the implementation of commercial p2p applications requires basic mechanisms to record transactions in the systems, i.e. the resource and service consumption, which will be used for charging, incentives, and control. These basic functionalities can be achieved by an accounting system that ideally should be fully distributed in keeping with the p2p spirit of such a system. Furthermore, it needs to be trustworthy so that the system cannot be misused by individual peers or groups of peers for gaining an undue advantage. Therefore, linking distributed accounting with distributed trustworthiness and distributed collaboration control presents a crucial challenge for the advancement of p2p systems. This dissertation researches this challenge by demonstrating the feasibility of fully distributed, trusted accounting in p2p systems with intrinsic automatic cooperation control by presenting and evaluating the token-based accounting scheme. The token-based accounting scheme’s framework introduces tokens as a combination of permission objects and receipts. Permission objects grant to peers the right to consume services and resources. When a peer consumes them, it “spends” tokens, and tokens becomes receipts which contain accounting information about the transaction. This process implements effective accounting with intrinsic cooperation control. The token-based accounting scheme’s system architecture is composed of four building blocks: Token structure, transaction protocols, token aggregation, and detection of double spending. The token structure ensures the authentication and integrity of accounting information, as well as the non-repudiation of transactions. The trustworthy transaction protocol introduces a novel transaction procedure that removes the benefits of defrauding the transaction partner but does not require the use of a third trusted party. Token aggregation swaps foreign tokens for new own tokens using a truly decentralised trustworthy process. With this process, a quorum of peers establishes a novel distributed basis of trust for p2p systems. This is achieved by applying threshold cryptography in combination with proactive secret sharing and with novel mechanisms that ensure the random selection of the quorum peers. The quorum size affects the scheme’s trustworthiness and is determined using a stochastic model. Efficient detection of double spending is enabled by introducing aggregation accounts that store issuing and usage information about tokens. Aggregation accounts are located at third party peers, called account holder sets. Maintenance operations performed on the account holder sets prevent loss of data and ensure consistency of aggregation accounts. Aggregation accounts are protected against attacks and fraud attempts by concealing their location using a novel overlay routing mechanism. By using simulations for several churn scenarios, the required account holder set size is determined. These simulations prove the token-based accounting scheme’s efficiency and the robustness of the storage mechanisms. The token-based accounting scheme was simulated in detail by varying the relevant parameters, i.e., quorum size, account holder set size, churn, and system size. The simulation results demonstrate the viability and efficiency of the novel token-based accounting scheme. Its applicability is shown in two application scenarios.
Official URL

The documents distributed by this server have been provided by the contributing authors as a means to ensure timely dissemination of scholarly and technical work on a non-commercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, not withstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.