Module 02

Blockchain Basics

If you've built on Ethereum or Solana before, skim this one — it's written for readers who have never touched a blockchain.

Wallets

A wallet is a keypair: a private key that proves it's you, and a public address safe to share. Your wallet is your identity and your signature — not a place money is literally "stored."

Transactions

A signed instruction — move this, call this contract, update this state. On most chains, transaction contents are fully public. On Midnight, a transaction can carry a proof that something is true without revealing the private inputs behind it.

Blocks & validators

Transactions bundle into blocks, each referencing the one before it. Midnight uses AURA to decide which validator produces each block, and GRANDPA as a separate layer that formally confirms blocks can't be reverted.

The concept to remember

Every other chain has one kind of state: public. A Midnight contract can hold three — ledger (public, on-chain), private(stays on the user's machine), and witness (private evidence that justifies a state change, without the evidence itself being recorded). Nearly every Midnight-specific bug you'll hit later traces back to mixing these up.