Blockchain's inherent property of immutability makes it an excellent tool for securing information and records. Once stored in a blockchain, data cannot be modified or updated. This is due to the distributed nature of the and its use of hash functions and cryptography. In this chapter, we'll be leveraging this feature of blockchain to build a module that will secure the contents of a document repository. To achieve this, we'll be using Hyperledger Fabric 1.4. Our solution will record hash signatures for the documents within a repository on a private Hyperledger Fabric network. It will then monitor all the recorded files and check at fixed time intervals to see whether the files have been tampered with or modified. Additionally, it'll check whether any new files have been added or modified. If any changes have been made, it will throw a notification and inform the user.

In this chapter, we'll be covering the following topics:

• Tamper-proof document storage using blockchain
• Setting up a Hyperledger Fabric network
• Writing and deploying the DocsApp chaincode 
• Building a node backend service
• Creating a React frontend for the app
• Running the tamper-proof application