Smart Contracts
Self-executing programs deployed on a blockchain that automatically enforce the terms of an agreement when predefined conditions are met. The building blocks of DeFi, tokenisation, and programmable money.
Smart Contracts
A smart contract is a program stored on a blockchain that executes automatically when predetermined conditions are met. Once deployed, the code is immutable and runs exactly as written — no intermediary can alter, censor, or stop it.
How They Work
- A developer writes contract logic in a language like Solidity (Ethereum) or Rust (Solana)
- The contract is compiled and deployed to the blockchain as bytecode
- Users interact with the contract by sending transactions
- The contract executes its logic deterministically across all nodes
- State changes are recorded on-chain and become permanent
Why They Matter
Smart contracts transform blockchains from simple payment networks into programmable financial infrastructure. They enable:
- DeFi protocols — lending, borrowing, trading without intermediaries
- Token issuance — creating and managing digital assets
- Automated settlement — instant, trustless execution of complex agreements
- DAOs — decentralised governance and treasury management
- Tokenisation — representing real-world assets on-chain
Key Properties
- Deterministic — same inputs always produce same outputs
- Immutable — cannot be changed after deployment (upgradeable patterns exist but add complexity)
- Transparent — source code is publicly verifiable
- Composable — contracts can call other contracts, creating complex financial primitives ("money legos")
- Trustless — execution is guaranteed by the network, not by any party
Risks
- Bugs are permanent — code vulnerabilities can lead to catastrophic losses (e.g. The DAO hack, 2016)
- Oracle dependency — contracts that need real-world data rely on external data feeds (oracles)
- Gas costs — complex operations can be expensive on congested networks
- Complexity — auditing smart contracts requires specialised expertise
The Bigger Picture
Smart contracts are the reason blockchain matters beyond simple payments. They enable the creation of an entirely new financial system — one that is open, programmable, and accessible to anyone. Every DeFi protocol, every tokenised asset, every stablecoin runs on smart contracts.