Generating dynamic merchant addresses using HD wallets

To generate dynamic addresses, we'll be creating a Hierarchical Deterministic (HD) wallet system for the merchant. HD wallets create a hierarchical tree of public and private keys from a single master node. This allows the user to generate and control a suite of public and private keys from the same seed phrase. The HD wallet owner can easily port their suite of keys to another hardware by porting the seed phrase used to derive the public-private key tree.

All addresses are generated from a master seed. Each time a new key pair is generated, the seed is extended at the end by a counter value. This means that, theoretically, you can generate 2⁵¹² key pairs from the same seed phrase. To back up their wallet, the user needs to back up just the master seed phrase. They can also move their key pairs easily between hardware...