Smart contracts are the code that runs trust — and where the risk lives.
What you will learn
Understand smart contracts and Solidity
Explain DeFi protocol design
Recognize contract risk and audit
State on-chain
State on-chain
Immutable history
Immutable history
What a smart contract is
A smart contract is code stored on-chain that executes automatically when conditions are met — no intermediary, no discretion. Written in Solidity (Ethereum) and similar languages, it's immutable once deployed (unless built to be upgradeable). 'Code is law' — for better and worse.
💡 A simple contract
A token contract tracks balances and allows transfers. An escrow contract releases funds only when both parties sign. A vault contract holds assets and issues shares. Each is just code, but once deployed and holding real money, it becomes a financial institution run by logic, not people.
DeFi protocol design
Designing a protocol means deciding: the asset (tokenomics), the incentive (who gets paid to do what), the access (permissionless?), the governance (who changes parameters), and the security (what an attacker could exploit). Every design choice is also a risk choice.
The audit imperative
Because contracts are immutable and hold real value, a single bug can drain everything. Professional audits, bug bounties, formal verification, and battle-testing are mandatory — not optional. The history of DeFi is written in unaudited contracts getting drained.
💡 Why audits matter
Reentrancy (the DAO hack), integer overflow, oracle manipulation, flash-loan exploits — each was a known class of bug that cost millions when someone skipped the audit. The lesson: security is not a feature you add; it's the architecture you build from line one.
The takeaway for investors
You don't need to write Solidity — but you must be able to read what a protocol does and whether it's been audited. 'Don't trust, verify' applies to the code, not just the chain. Invest only in protocols whose security you can reason about.