🔐 What Are Private Keys and Public Keys in Crypto?

While developing a wallet application, I realized it's essential to have a solid understanding of how private and public keys work. These fundamentals are not just academic — they directly influence how securely and efficiently a wallet operates.

🔑 What Is a Private Key?

A private key is a randomly generated 256-bit (32-byte) number. It gives full control over a wallet’s funds.

Example:

0C28FCA386C7A2276AC8192E9F6DDEDC6D1E2C140C3C7A75A2B708F3EDF5BE59

There are 2^256 possible keys — more than atoms in the universe — making it virtually unguessable.

🔓 What Is a Public Key?

The public key is derived from the private key using elliptic curve cryptography (ECC). In Bitcoin, this is done with the secp256k1 curve. It's a one-way process — safe and irreversible.

🧾 How Is an Address Created?

1. Start with public key
2. Hash it (SHA-256 → RIPEMD-160)
3. Add version byte
4. Add checksum
5. Base58Check encode the result

This becomes a Bitcoin address.

🔄 Key Derivation Diagram

[ Private Key ]
     ↓
[ Public Key ]
     ↓
[ Public Key Hash ]
     ↓
[ Address ]

🌲 HD Wallets in a Nutshell

Later in this journey, we’ll explore HD Wallets in more depth — especially how they're implemented in Rust and used to generate secure, deterministic key hierarchies for modern wallet applications.

HD (Hierarchical Deterministic) wallets generate thousands of addresses from a single seed using a structured path like:

m / 44' / 0' / 0' / 0 / 0

Only the seed phrase needs to be backed up.

💡 Why Different Formats Exist

Each format is optimized for the platform’s cryptography and UX.