# A Time Bank System Design on the Basis of Hyperledger Fabric Blockchain
## 1 Introduction  
The concept of time-based currency was created decades ago. However, the term \"time bank\" was first raised by [PERSON] in 1992 [1], and he also promoted an important philosophy: \"equal time, equal the value\". Years later, in 1995, he founded the Time Dollar Institute which is known as the \"TimeBanks USA\" today. What is the meaning of time banking or a time bank system? In a nutshell, a time bank system is a reciprocity-based work trading system where time is valuable as a currency. In [PERSON]'s book [2], he listed five core values of a time bank system which are: \"asset, redefining work, reciprocity, social networks, and respect\". These core values spread around the world and motivated people worldwide to establish various time bank systems in their own communities. In the outbreak era of influenza and viruses, especially COVID-19 these days, the necessity and importance of building mutual assistance within communities increased significantly. This fact motivates us to devote ourselves to build tools and/or systems for straightening out the chaotic situation we are facing. As shown in this work, with the aid of modern technology such as blockchain, a time bank system could manifest its value in building community, inclusion, volunteerism, and social assistance.  
Typically, a time bank system is held by a time bank committee and built in a local community. Furthermore, the system is exclusive, whereby only people who are known to the committee can join the system. Agents of a time bank have to manage every legal member's request-or-supply for a service through phone calls and record them on notebooks, before manually matching up the demand and thesupply for services, all of which are complicated tasks. Moreover, an exhaustive service recording is also very time-consuming.  
All the works need to be handled, within a local or domestic district, by time bank system employees. It would be a good idea to transfer the function of a time bank system to the internet so as to enable the participants to directly upload their service demands and supplies to the internet, even though mobile devices.  
However, these time bank systems are centralized in nature. Although a centralized system benefits the system's efficiency a lot, the participants have to build their mutual trust by relying on a trusted third party (TTP), the time bank system's administrant. A recent technology called blockchain provides a decentralized platform that allows people to interact with each other without any mediator or central controller. In this work, a blockchain-based time bank system was designed and realized on the basis of the Hyperledger Fabric framework.  
This work is organized as follows: Section 2 gives the reason for choosing Hyperledger Fabric as our system implementation backbone and reviews some related works on blockchain-based time bank systems. Section 3 offers function-level overviews of the proposed system. The involved functional modules are explained in Section 4. Section 5 presents the implementation details of the proposed system and reports some measured performances. Challenges that our system might encounter in real-world applications are firstly depicted in Section 6. Finally, the conclusion and our future research directions are presented.