Оракул
Blockchain Oracle
A blockchain oracle is a service that feeds external data to smart contracts, such as prices, event results, exchange rates, and payment statuses.
What is Оракул (Blockchain Oracle)?
A smart contract can only work with data inside its own blockchain network. It cannot query a website, exchange, or bank on its own. An oracle solves this problem: it retrieves external information and writes it to the blockchain as a transaction that the contract can use.
## How it works
An oracle consists of a data source, a collection and delivery mechanism, and a verification layer. A simple flow: external API or exchange → oracle nodes receive the value → values are aggregated (median, mean, or weighted value) → the result is published to the network. The contract reads the published value and makes a decision, for example, whether to liquidate a position.
## Types of oracles
Inbound oracles bring external data into the network. Outbound oracles send commands from the network to the outside world, for example, triggering a payout through a banking gateway. Centralized oracles rely on a single provider and carry the risk of a single point of failure. Decentralized oracles combine multiple independent nodes that stake collateral and can be penalized for submitting incorrect data.
## Where it is used
Oracles are most commonly used in DeFi to calculate asset prices for lending and liquidations, in derivatives and stablecoins, in prediction markets that need an event outcome, and in games tied to external data. For on-chain gambling and betting products, oracles supply match results and odds.
## What it affects
The quality of an oracle directly determines whether a contract works correctly. A delay or an incorrect price value can trigger unjustified liquidations or payouts. Manipulating the source, for example through a short-term price distortion in a thin market, is one of the most common causes of losses in DeFi.
## Common mistakes
FAQ
Why does a smart contract need an oracle?
A smart contract has no direct access to external data. An oracle brings the required information, such as a price or an event result, onto the blockchain so the contract can rely on it.
What are the risks of oracles?
The main risk is incorrect or tampered data. If an oracle is centralized or its source is easy to manipulate, the contract will execute an incorrect action, and recovering the funds can be difficult.
What is a decentralized oracle?
It is a network of independent nodes that collect data from multiple sources, aggregate it, and back the result with their collateral. Nodes that submit faulty data are penalized.