You can easily extend the concepts covered in the projects in this book to other applications. Following are a few examples of modules that can be modified and extended to other applications:

• Wallets: As we discussed earlier, wallets are the most common module across blockchain applications. It's almost impossible to build a blockchain application without it. Wallets that hold fungible and non-fungible tokens can be used as payment wallets, digital identity cards, smart cards, ownership documents, and custodians of other transferable and non-transferable assets.
• Tokens: Tokens form the building blocks of many blockchain applications. Tokens can be used to represent a myriad of fungible and non-fungible assets for accounting purposes in blockchains. In cases where you need to track provenance and auditability of a real-world asset, it is typically issued or represented as a token on a blockchain system for accounting purposes. At the same time, you can use tokens to represent virtual assets as well.
• Hierarchical Deterministic (HD) Wallets: HD wallets are fairly common across most Ethereum and Bitcoin wallets as they are easy to maintain, operate, and transfer. This includes MetaMask. You can extend this concept to run a Custodian Wallet system for customers, where you receive payments or other assets on a public blockchain network on their behalf. The private keys in such a scenario should ideally be stored in an HSM infrastructure and the service provider should be accountable for the safety of the assets.

• Payment gateways: In permissionless systems, you can use the payment gateway module for receiving and tracking any kind of assets, not necessarily financial ones. Since most permissioned systems follow a deterministic consensus protocol, the block confirmation feature of our payment gateway would probably not be very useful. However, if your permissioned network uses a probabilistic block-based consensus protocol, you could easily configure the payment gateway module to receive and confirm receipt of any transferable asset.
• Document share using IPFS: The document share feature used in the Corporate Remittance project can be implemented across different financial services. By establishing an IPFS network between the nodes, you can easily share documents securely between network participants. By default, IPFS does not replicate documents between network participants. It only establishes a protocol by means of which you can fetch the file from other IPFS nodes on the network that have a copy of the file. You could also set up an IPFS cluster network that automatically replicates IPFS published files across all of the IPFS cluster nodes.
• Building a Hyperledger Fabric network from scratch: The corporate remittance chapter also walks you through setting up a custom Hyperledger Fabric network. You can modify the scripts and the Docker Compose yaml files for custom applications and use cases.
• Chaincodes: Chaincodes are Hyperledger Fabric's version of a smart contract. You can use them for different use cases owing to their flexibility.
• Building a local Stellar network: You can follow the steps used for setting up the Stellar network between the banks with minor modifications for setting up a development environment for various blockchain use cases implemented using Stellar.
• Issuing and transferring assets on Stellar: You can issue and transfer different types of assets on the Stellar network. These could be financial or non-financial.
• Automatic blockchain workflows: The chapter on Letters of Credit only gives a small taste of the power of Ethereum smart contracts. You can use smart contracts to re-engineer existing legacy workflows to be faster, more efficient, and transparent.
• Tamperproof files, directories, and documents: The tamperproof application has multiple applications as is. Additionally, you can probably connect the application to a virtual or physical backup to allow any resources that have been tampered with to be restored.

• Decentralized trading exchanges: Decentralized trading exchanges can be used for trading a wide variety of assets. They can include any kind of securities, financial or non-financial assets, tokens, bills, and so on.
• Cross-asset payments: For carrying out cross-asset remittances, you can integrate an external API to fetch conversion rates for various base and counter currencies. Optionally, you can use Stellar's order book, provided there are offers posted to it. You can look at the concept of Path Payments in Stellar, which carry out transactions in hops, each hop indicating the conversion of one asset into another.

Next, let's look at some additional blockchain concepts that you might want to find out more about.