A Blockchain-based Micro-Economy of Bandwidth Tokens

A challenging problem in decentralized systems is encouraging long-term cooperative behaviour between strangers. It is often not immediately bene_cial to cooperate without the guarantee of direct reciprocity. Cooperation among entities in the long term results in sustainability while sel_sh behaviour can lead to the collapse and distrust of such communities. This collapse is also referred to as the tragedy-of-the-commons phenomena and is notoriously hard to prevent when considering mutual access to resources [2]. Our aim is to incentivize network participants in _le-sharing communities to cooperate with each other by introducing monetary rewards for good behaviour. We explore whether a _le-sharing ecosystem based on band- width tokens is capable of addressing the tragedy-of-the-commons and increase cooperation and sustainability in general. Blockchain technology is used to achieve tamper-proof accounting of such bandwidth tokens. While blockchain is often used to securely maintain digital currencies without _nancial institutions, our goal is to deploy a distributed ledger to promote cooperation amongst content providers and consumers. Based on this goal, we designed a blockchain with superior scalability, compared to existing blockchain solutions [4]. A high-level system architecture of our micro-economy is presented in Figure 1. The key component of our design is a bandwidth token, irrefutably stored and tracked on our deployed blockchain fabric: TrustChain [4]. TrustChain is speci_cally designed to build trust between interacting strangers and has no hard requirement for global consensus, in comparison to popular blockchain applications. Instead, consensus is reached between transacting parties and fraud is guaranteed to be eventually detected by the means of network gossiping. In contrast to existing blockchains like Bitcoin or Ethereum, each user creates and grows their own chain of transactions [3]. Every transaction in TrustChain is dual-signed and stored in the chains of both transacting parties. Our approach yields superior scalability while signi_cantly reducing storage requirements. Content providers are able to mine or earn bandwidth tokens by uploading content to others using our decentralized _le sharing client Tribler [1]. Token mining is an autonomous process that attempts to optimize the amount of uploaded data by _rst downloading and then uploading a subset of available content. Mining is both bene_cial for the provider, who earns spendable tokens, and the community, where contributed bandwidth results in faster downloads and increased availability of content. Content consumers pay providers for their provided resources with bandwidth tokens. When the di_erence between the amount of uploaded and downloaded bytes (the token balance) of a speci_c user is below a certain threshold, content providers refuse to upload content to these peers, until they contributed a su_cient amount of bandwidth back to the community. This basic but e_ective free-riding policy makes bandwidth tokens usable and ensures that there is a basic demand for them. We address privacy issues arising from sharing content with a deployed and tested Tor-like communication overlay. When this overlay is enabled, an end-to-end encrypted path is constructed with other nodes and tra_c is routed through these nodes. This allows peers to interact with the community in an anonymous way. In contrast to Tor, the anonymous layer as implemented in Tribler is fully decentralized and does not rely on centralized (directory) servers. The system o_ers anonymity at the cost of increased bandwidth requirements