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Oracles

How the SortedOracles smart contract uses governance to collect reports and maintain the oraclized rate or the Celo dollar.

SortedOracles Smart Contract​

As mentioned in the previous section, the stability mechanism needs to know the market price of CELO with respect to the US dollar. This value is made available on-chain in the SortedOracles smart contract.

Collecting Reports​

Through governance, a whitelist of reporters is selected. These addresses are allowed to make reports to the SortedOracles smart contract. The smart contract keeps a list of most recent reports from each reporter. To make it difficult for a dishonest reporter to manipulate the oraclized rate, the official value of the oracle is taken to be the median of this list.

Maintaining Oracle Values​

To ensure the oracle's value doesn't go stale due to inactive reporters, any reports that are too old can be removed from the list. "Too old" here is defined based on a protocol parameter that can be modified via governance.

Celo-Oracle Repository​

You can find more information about the technical specification of the Celo Oracles feeding data to the reserve in the GitHub repository here.