Harbinger

Harbinger is a Self-Sustaining Price Oracle for Tezos. Harbinger is a set of tools and reference contracts that allows anyone to become a poster. As a poster, they can deploy a price oracle on the Tezos network that will publish cryptographically signed prices. Additionally, Harbinger includes a reference signer that an exchange, at a low cost, can deploy in order to provide a signed price feed compatible with Harbinger. Harbinger was inspired by Compound’s Open Price Feed, but adds some additional features. Essentially, the process works as follows: first, the signer retrieves market data from an exchange and signs it with a private key. A poster can then retrieve prices from the signer and post them to the storage contract. Optionally, a poster can invoke a callback on the storage contract that will push the price data to a normalizer contract. The normalizer contract calculates a volume weighted average price, which gives price data consumers assurance that the normalized price won’t be influenced by low-volume price outliers. Finally, any DeFi protocol may invoke a callback on the normalizer contract in order to have the latest normalized price pushed to their own contract.