Smart contract

What is a smart contract in simple words

A smart contract is a self-executing digital program that automatically fulfills the terms of a deal when the participants meet the predetermined rules. It is a digital agreement that works in the blockchain and eliminates the need for intermediaries (notaries, lawyers, banks or arbiters). Imagine a coffee vending machine. You select a drink and insert the required amount (fulfill the condition). The machine checks whether there is enough money and gives out coffee and change (automatic execution works). In the digital world, a smart contract works the same way, only instead of the machine there is secure code running in the blockchain. The principle: “If A happens, then B occurs”. Example: “If the flight is delayed by 3 hours (condition A), then the insurance automatically pays the client $100 (action B)” — and this happens without human involvement, without submitting applications and without waiting. Smart contracts are the basis of the modern crypto industry and decentralized finance (DeFi). You can learn more about the ecosystem in the article Decentralized finance (DeFi).

How a smart contract works

The operation of a smart contract is built on several key principles that ensure its reliability, transparency and automation. Conditions — the parties prescribe the logic of the deal in code in a specialized programming language (for example, Solidity for Ethereum, Rust for Solana) and upload the contract to the blockchain. The code contains all the conditions: who, what, when and under what conditions must do it. Verification — the blockchain network (validator nodes) automatically tracks the fulfillment of conditions. This happens in a decentralized way: thousands of independent nodes check transactions and confirm their correctness. Execution — if the conditions are met (for example, the goods are delivered, the fact of the event is confirmed, the required amount is received), the contract automatically performs the programmed action: transfers funds, transfers ownership, issues a token, pays insurance. All this happens without the possibility of cancellation, since the blockchain ensures the immutability of records. Transparency — the smart contract code is available for review by any participant (if it is not encrypted), which ensures trust between the parties. Immutability — after deployment in the blockchain, a smart contract cannot be changed or deleted (except for special update mechanisms that must be provided in advance by the developer). All this makes smart contracts an ideal tool for automating trust relationships in the digital environment.

Main advantages

Using smart contracts gives deal participants a number of significant advantages compared to traditional paper agreements. Honesty and accuracy — the program works strictly according to the prescribed algorithm. Neither party can change their mind, change the terms retroactively or refuse to perform. The human factor is excluded: errors, misunderstandings, delays, subjective interpretations. Reliability — the smart contract is stored in the blockchain, it cannot be forged, deleted or canceled. All transactions are recorded in the distributed ledger and available for verification. Economy — intermediaries (lawyers, notaries, banks, arbiters) are excluded from the deal chain, which reduces fees and speeds up the process. There is no need to pay for legal support, paperwork, intermediary services. Speed — execution happens automatically and instantly (within the transaction confirmation time in the blockchain — from a few seconds to a few minutes), not through days or weeks, as in traditional processes. Transparency — all conditions and operations are available for verification, which increases trust between the parties and simplifies dispute resolution. Accessibility — smart contracts are available to any user with the internet and a crypto wallet, regardless of geographical location and the presence of a bank account. Read about how blockchain technology works in the article Blockchain.

Where smart contracts are used

Smart contracts find application in a wide variety of industries, and their use is constantly expanding. DeFi (Decentralized Finance) — automatic lending, token exchange, staking, yield farming, insurance payments. Smart contracts provide all operations in DeFi protocols. Logistics and supply chains — automatic payment upon confirmation of cargo delivery (for example, through IoT sensors tracking location and temperature). NFT and games — issuance, sale and tracking of ownership rights to digital assets, automatic royalty payments to authors upon resale. Voting and management (DAO) — decentralized autonomous organizations use smart contracts for voting and automatic execution of community decisions. Insurance — automatic payments upon the occurrence of an insured event (for example, flight delay, crop failure, natural disaster) based on data from external sources (oracles). Real estate — automatic registration of the transfer of ownership rights when the terms of the deal are met, rental with automatic debit of payments. Digital rights management — automatic licensing, royalty payments, control of content use.

Risks of smart contracts

Despite all the advantages, smart contracts are associated with a number of risks that must be taken into account when developing and using them. Errors in code (vulnerabilities) — the main risk of smart contracts. If the developer made a mistake, attackers can use it to steal funds or manipulate. Examples: The DAO (2016, $60 million stolen), Parity Wallet (2017, $300 million frozen), Re-entrancy attacks. Immutability — after deployment, the contract cannot be fixed. If there is an error in it, it cannot be corrected without special update mechanisms (which must be provided in advance). Dependence on oracles — to obtain data from the outside world (prices, weather, events), smart contracts use oracles. If the oracle is compromised or gives incorrect data, this can lead to incorrect execution. Legal uncertainty — in many jurisdictions, the legal status of smart contracts is not fully defined, and in case of a dispute, the court may not recognize their legal force. Gas (network fee) — performing each operation in a smart contract requires paying a fee (gas), which can be very high when the network is overloaded. Human factor — users can make mistakes when interacting with the contract (send funds to the wrong address, specify incorrect parameters). Before using a smart contract, it is important to check its security audit, conducted by well-known firms (CertiK, Hacken, Trail of Bits). Read about protection from cyber threats in the article Information security incident.