What is a smart contract?

A smart contract is a self-executing program stored on a blockchain that automatically enforces the terms of an agreement between two or more parties. When predefined conditions are met, the contract executes itself, without the need for intermediaries or manual intervention. In this article, our blockchain expert Diego González explains what smart contracts are, how they work technically, where they came from, and what legal and security considerations businesses should keep in mind before adopting them.

The origin of smart contracts: who invented them and when?

The concept of smart contracts is older than most people think. It was not born with Bitcoin or Ethereum. The term was coined by Nick Szabo, a cryptographer and computer scientist, in the early 1990s. Szabo envisioned contracts written in code rather than natural language, enforced automatically by a computing system rather than courts or lawyers. His classic example was a vending machine: you insert money, select a product, and the machine delivers it automatically. No human intervention, no trust required.

The problem at the time was that the technology needed to execute this vision reliably did not exist yet. That changed with the rise of blockchain. When Bitcoin launched in 2009, it demonstrated that decentralized, tamper-resistant record-keeping was possible. Then, in 2015, Ethereum introduced a programmable blockchain specifically designed to run smart contracts. The 2017 cryptocurrency boom brought smart contracts into mainstream awareness, driven largely by the explosion of decentralized applications and token sales built on Ethereum.

How does a smart contract actually work?

At its core, a smart contract follows a simple logic: if condition X is met, then execute action Y. The contract lives on the blockchain, meaning it is distributed across thousands of nodes, and no single party can alter or stop it once deployed.

The anatomy of a smart contract

Understanding the basic structure of a smart contract helps clarify why they behave the way they do. A typical smart contract contains the following components:

• Parties: The addresses (accounts) of the entities involved in the agreement.
• Conditions (triggers): The specific events or data inputs that activate the contract. For example, “payment received” or “delivery confirmed.”
• Logic and rules: The code that defines what should happen when conditions are met. This is the core of the contract.
• Execution output: The actions taken automatically once the conditions are satisfied, such as transferring funds, recording data, or issuing a document.
• State: The current status of the contract (active, completed, pending), stored on-chain.

On Ethereum, smart contracts run on the Ethereum Virtual Machine (EVM), a sandboxed runtime environment that processes contract code consistently across all nodes. Other blockchains, such as Solana or Cardano, use non-EVM environments with different programming languages and execution models.

What are oracles and why do they matter?

Smart contracts on their own can only access data that already exists on the blockchain. But most real-world business scenarios depend on external information: price feeds, weather data, shipping confirmations, or regulatory status updates. This is where oracles come in. An oracle is a service that connects a smart contract to off-chain data sources. It acts as a trusted data bridge, feeding verified external information into the blockchain so the contract can react to real-world events.

For example, a supply chain smart contract might use an oracle to confirm that a shipment has arrived before automatically releasing payment. The reliability of oracles is critical. If the data fed by an oracle is wrong or manipulated, the contract will execute incorrectly, regardless of how well the code is written. This is known as the oracle problem, and it remains an active area of development in the blockchain space.

Smart contracts and blockchain: the broader context

Smart contracts do not exist in isolation. They are a fundamental building block of what is often called Web3, the next generation of internet infrastructure built on decentralized protocols. Within this ecosystem, smart contracts power:

• Decentralized Finance (DeFi): Lending, borrowing, and trading without banks or brokers.
• NFTs (Non-Fungible Tokens): Digital ownership records for assets like art, music, or real estate.
• DAOs (Decentralized Autonomous Organizations): Organizations governed by code rather than traditional management structures.
• Supply chain automation: Automatic payments and document issuance when logistics conditions are met.
• Document certification: Verifying the authenticity and integrity of digital documents without a central authority.

For businesses, the most relevant applications tend to be in areas where trust between parties is costly to establish and maintain, and where automation can reduce administrative overhead significantly.

Are smart contracts legally binding?

This is one of the most important questions for any business evaluating smart contract adoption, and the answer is nuanced. A smart contract is not automatically a legally binding contract simply because it runs on a blockchain. For a contract to be legally valid in most jurisdictions, it typically needs to satisfy certain basic requirements:

• Offer and acceptance by the parties involved.
• Intention to create legal relations.
• Consideration (something of value exchanged).
• Capacity of the parties to enter into a contract.
• Legality of the subject matter.

A smart contract can satisfy these requirements, but it depends heavily on how it is designed and what legal framework governs it. In some cases, a smart contract might serve as the execution layer of a traditional legal agreement signed elsewhere. In others, the code itself is intended to be the entire contract.

The phrase “Code is Law” captures the philosophical position that the code of a smart contract should be treated as the definitive expression of the parties’ agreement. If the code executes, the contract is fulfilled, regardless of what anyone intended. This approach has appeal for its certainty, but it also raises serious problems when code contains errors or when outcomes conflict with what the parties actually agreed to.

What are the main legal challenges of smart contracts?

Smart contracts introduce several legal challenges that traditional contract law was not designed to handle. Understanding these is essential for businesses considering adoption.

Enforceability across jurisdictions

Blockchain networks are global and borderless, but contract law is national. A smart contract executed between parties in different countries may be subject to conflicting legal systems. Determining which jurisdiction governs the contract, and how disputes would be resolved, is not straightforward.

Error correction and immutability

Once deployed on a blockchain, a smart contract is generally immutable. This means that if there is a coding error or if circumstances change, the contract cannot easily be altered. Traditional contracts can be renegotiated or corrected. Smart contracts, by default, cannot. This creates a significant legal and practical problem when bugs lead to unintended outcomes.

Dispute resolution

If a party disputes the outcome of a smart contract execution, there is no obvious forum for resolution. Traditional courts may struggle to interpret code as a legal document. Arbitration mechanisms built into smart contracts are being explored, but they are not yet standardized or widely recognized.

Proof in court

Using blockchain records as evidence in legal proceedings is still an evolving area. While blockchain data is tamper-resistant, courts in many countries have not yet established clear rules for how on-chain evidence should be treated or authenticated.

The path toward legal standardization

Several jurisdictions are moving toward recognizing smart contracts in law. For example, some US states have passed legislation explicitly recognizing blockchain-based smart contracts as legally valid. The European Union is developing frameworks under initiatives like eIDAS 2.0 that may eventually accommodate smart contract signatures and execution. Progress is happening, but it is gradual and uneven across countries.

Smart contracts vs. traditional contracts: what is the difference?

Smart contracts do not replace traditional contracts. In most real-world scenarios, they complement them. Here is a practical comparison:

• Traditional contracts are written in natural language, interpreted by humans, and enforced by courts or arbitrators. They are flexible, can be renegotiated, and handle ambiguity through judicial interpretation.
• Smart contracts are written in code, interpreted by machines, and enforced automatically by the blockchain. They are precise but rigid. They eliminate the need for a trusted third party but cannot easily accommodate nuance or intent.

The most effective implementations often combine both: a traditional legal agreement sets the overall framework and intent, while a smart contract handles the automated execution of specific, clearly defined obligations within that framework.

What security risks do smart contracts carry?

Smart contracts are only as good as the code they are built on. Because they are immutable and often control significant assets, security vulnerabilities can have serious consequences. Common risks include:

• Code bugs: Programming errors that cause unintended behavior. The most famous example is the 2016 DAO hack, where a reentrancy vulnerability allowed an attacker to drain approximately $60 million worth of Ether.
• Logic errors: The code does what it was written to do, but the logic does not reflect the intended business outcome.
• Oracle manipulation: Feeding false data into a contract to trigger an incorrect execution.
• Upgrade risks: Some contracts are designed to be upgradeable through proxy patterns, which introduces new attack surfaces.
• Dependency vulnerabilities: Smart contracts that rely on other contracts or external libraries can inherit their bugs.

For businesses, this means that security audits by qualified professionals are not optional before deploying any smart contract that handles sensitive data or financial transactions. The immutability that makes smart contracts reliable also makes mistakes very difficult to fix after the fact. certification, do not hesitate to contact us. We will be delighted to help you!