Blockchain oracle

A contract cannot freely query an external API during consensus execution. An oracle introduces data through transactions, signatures or another verifiable mechanism so the network processes the same input.

Designs may aggregate sources and use multiple operators. They may also rely on one authority when a fact has a single legitimate issuer. A signature establishes origin rather than data accuracy.

Assessment covers freshness, outliers, source liquidity and error behavior. A decentralized source may reduce specified dependencies without guaranteeing always-correct information.