Smart contract

A Smart Contract is a stand-alone, self-executing computer program deployed on a blockchain network, which executes predefined instructions in a way deterministic, transparent and immutable when certain conditions are met. These contracts automate the execution of agreements that already exist, reducing manual involvement by banks, platforms or administrators, with maximum traceability. They do not replace the legal contract or the formalities the law requires: a public deed and a land-registry entry are still needed where the law imposes them. The contract is the source of the right; the smart contract only executes it (Arts. 1279 and 1280 of the Spanish Civil Code).

The code of a smart contract:

• It is written in specific languages such as Solidity (EVM), Rust (Solana/NEAR), Move (Sui/Aptos).
• It is deployed on a public or private blockchain through a transaction.
• It allows you to execute functions such as token transfers, logical validations, issuance of NFTs, votes, auctions or financial flows.
• It uses a model of shared global status, where each execution can modify balance sheets, issue events or interact with other contracts.

Key Features:

• Immutability: once deployed, it cannot be modified (unless programmed with update logic).
• Decentralization: its execution is validated by the entire network.
• Transparency: The code and interactions are public.
• Automation: responds automatically to defined actions, without permissions or external intervention.
• Cryptographic security: any execution is signed and recorded.

Use cases:

• DeFi: loans, exchanges, stablecoins, derivatives.
• NFTs: creation, transfer, royalties.
• DAOs: decentralized governance, on-chain voting.
• Tokenization: legal or financial representation of real assets.
• Digital identity: verification, authentication and permissions.
• Gaming: reward mechanics, in-game economy, digital property.

Its correct design requires rigorous testing, error control and professional audits, since a vulnerability in a smart contract can cause irreversible losses, given the immutability of the blockchain environment.