An agent that finds and verifies information, bridging the real world and the blockchain by providing data to smart contracts for execution of said contracts under specified conditions.
Software and hardware oracles fetch data from different sources. For example, software oracles get data from internet-based services such as servers and databases, while hardware oracles receive data from information-reading gadgets such as barcode scanners.
Inbound oracles deliver off-chain data to smart contracts while their outbound counterparts relay information from contracts to the real world. Oracles that rely on a single data provider are centralized while those that interact with multiple sources are considered decentralized.
Although multiple contracts and decentralized systems can reference one oracle, there are contract-specific oracles built to serve a single smart contract. Note that individuals with unique subject knowledge can fetch, verify, and validate data for use by blockchain-based agreements. These are known as human oracles.
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