# Research on Blockchain-Based E-Bidding System
## 2 Preliminaries
### Hyperledger Fabric  
Hyperledger is the most representative consortium blockchain at present. Hyperledger Fabric (HLF), the cornerstone of the Hyperledger project, is an open-source enterprise-levellicensed Distributed Ledger Technology (DLT) [20] platform, which was originally created by IBM and Digital Asset. In the HLF platform, all participants must be authenticated before they can participate in the transaction on the blockchain. On the one hand, HLF supports smart contracts such as Ethereum, which describe and execute the application logic of the system. On the other hand, Hyperledger is different from public blockchains such as Ethereum or Bitcoin. The following points describe how to mitigate the limitations of an Ethereum-based system in an HLF-based framework:  
1. In the HLF framework, traditional programming languages such as Java and Go can be used to write smart contracts for chaincode. 2. All the chaincodes in the framework run on the Dockers container. The modular nature of the different components and chaincodes in the container enables it to achieve flexibility, versatility and reusability of various goals. 3. HLF also introduces the concept of multichannel, which enables different services to run on different channels and ensures data isolation between nodes connected to the channel. As a result, HLF does not require anonymous miners to verify the transaction, nor does it require expensive mining calculations to submit the transaction; that is, it does not require related currencies as incentives. Therefore, it not only saves time and money, but also increases the scalability of the transaction. 4. As the open-source framework of the consortium blockchain, Hyperledger is biased towards the characteristics of the consortium architecture in design. All or part of the permissions are only available to members of the consortium. Usually, according to the consortium consensus designated several nodes to record the ledger, other nodes only participate in the transaction and read the relevant information authority. Therefore, the consortium blockchain can achieve higher transaction efficiency and meet the needs of decentralization at the same time. In addition, the privacy of data can be protected to a certain extent. To sum up, Fabric is one of the platforms with better performance in transaction processing and confirmation delay. It realizes smart contract and transaction privacy and confidentiality. HLF has a flexible and modular architecture. It supports open and standard protocols [21] and has different functions. The HLF has the following significant features:  
* Chaincode: Similar to smart contracts in the Ethereum network, it is a script written in a more advanced language, and all transactions executed are permanently stored in a ledger, where all participants can view this information. Chaincode is a superset of smart contracts; that is, smart contracts manage the business logic, and chaincode manages the smart contracts defined within them. * Channel: A dedicated communications subnet used to transfer confidential data between multiple network members. Activities on a channel are visible only to associated and authorized entities. * Endorser: The endorser invokes chaincode to validate the transaction and return the result of the endorsed transaction to the application. * Membership services provider (MSP): MSP is used to identify a trusted certificate authority (CA) to define members of the trust domain, to provide authentication and access control by issuing and verifying certificates, and to determine the specific roles (members, administrators, etc.) that members may play in the blockchain network. These characteristics of Fabric make it a highly scalable system. It is a highly modular and configurable architecture that can provide diversity, innovation and optimization for businesses of many fields, so it can support various industrial applications from finance, supply chain, healthcare to tendering and bidding.