Oracle
A service that supplies external data to a distributed ledger, bridging real-world facts and on-chain logic.
Blockchains cannot observe the outside world. An oracle delivers verified external data — a price, a sensor reading, a verification attestation — so a contract can act on it.
The design problem is trust. A single oracle is a central point of failure and manipulation, so robust systems use multiple independent sources, cryptographic attestations and dispute windows before data is treated as final.
In carbon applications, oracles typically carry attestations from verifiers or registry state. Their integrity determines whether automated issuance means anything: a compromised feed issuing credits for reductions that never happened is the failure mode to design against.
Frequently asked questions
Why can't a contract just read a website?
Because consensus requires every node to reach the same result deterministically; arbitrary web content does not satisfy that.
What makes an oracle reliable?
Independence of sources, transparent methodology, economic incentives against misreporting, and a dispute mechanism.