Overview
A blockchain oracle is a third-party service for smart contracts. Oracles provide trusted information based on the outside-world sources to the on-blockchain smart contracts. An oracle typically encapsulates the real-world complexity outside of the blockchain. This provides different engineering advantages, chiefly that critical errors and potential points of failure are easier to mitigate off-chain than on-chain.
For example, in a contract to automatically purchase bitcoins at a predetermined price, the fulfillment condition is based on the current exchange rate for the bitcoin; an off-chain oracle can constantly monitor the price to provide the triggering condition to the contract.
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Concerns
If an oracle relies on a single source of truth (centralized), that can lead to issues: the data source can be hacked in a man-in-the-middle attack, or altered by its owner, in order to sway smart contracts. Decentralized oracles (consensus oracles) increase the reliability of the information provided to smart contracts by querying multiple data sources, thus distributing trust between participants. However, this does not achieve trustlessness, since oracles are not part of the main blockchain consensus, and thus not part of the security mechanisms of public blockchains.
2 sources for this section
- 1Blockchain oracle — Wikipedia, revision 1346355893
- 2Casino, Fran; Dasaklis, Thomas K.; Patsakis, Constantinos (March 2019). "A systematic literature review of blockchain-based applications: Current status, classification and open issues". Telematics and Informatics. 36: 55–81. doi:10.1016/j.tele.2018.11.006.
The source notesEvidence & further reading2 sources
- Blockchain oracle — Wikipedia, revision 1346355893 Wikipedia contributors · Reference source · accessed 2026-09-22
- Casino, Fran; Dasaklis, Thomas K.; Patsakis, Constantinos (March 2019). "A systematic literature review of blockchain-based applications: Current status, classification and open issues". Telematics and Informatics. 36: 55–81. doi:10.1016/j.tele.2018.11.006. doi.org · Reference source · link imported 2026-09-22
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