Median Feeds and Proof Feeds

You can find currently deployed MedianFeeds and ProofFeeds contracts on this page.

Overview

Chunk’s second oracle system — MedianFeeds + ProofFeeds — is optimized for networks where gas costs are typically high (e.g., Ethereum). It separates data collection from verification, ensuring economical updates while maintaining rigorous security guarantees.

• MedianFeeds: Collects validator-submitted prices and computes medians.
• ProofFeeds: Verifies values using Merkle proofs and signatures before recording them on-chain.

This dual-layer approach dramatically reduces costs while enabling robust and verifiable oracle data.

MedianFeeds

Data Collection Validators write prices in a cost-effective side network (e.g., Chunk chain, with fallback to another inexpensive chain). Once a quorum is reached for each metric, the contract calculates the median price and stores it.

Workflow:

• Epoch duration: ~5 minutes.
• Validators submit direct transactions (not multiparty — synchronization is time-based).
• Median for each metric is computed and stored.
• A signed Merkle root tree of the previous epoch is also stored.
• This can serve as a primary source or a backup oracle, since the signatures remain valid across both scenarios.

Validators:

• Collect values for a large number of metrics.
• Write all values to MedianFeeds.
• At the end of each epoch:
  • Retrieve values of all metrics at the block’s end.
  • Construct a Merkle tree and compute its root.
  • Sign the Merkle root via a multiparty mechanism for each target network.
  • Submit the root + signatures to MedianFeeds.

ProofFeeds

How to update the Proofs Oracles by yourself you can find on this page.

ProofFeeds is designed for high-cost networks like Ethereum, where every transaction matters. Instead of storing raw values, it stores only Merkle roots and verifies values against them using proofs.

Workflow:

• Accepts inputs:
  • Merkle root
  • Signatures
  • Proof
  • Metric value
  • Timestamp
  • Epoch
• Validates that:
  • The root signature is correct.
  • The Merkle proof is valid for the given root.
• Once verified, the metric value is stored and exposed via ICoreMultidataFeedsReader.

Key Advantages

Innovative Data Retrieval

The MedianFeeds + ProofFeeds combination enables nearly indefinite data retrieval on Ethereum. This approach expands blockchain data capacity and access far beyond traditional methods.

Unmatched Cost-Efficiency

By separating collection and verification:

• Prices are collected in low-cost networks.
• Only compact proofs are verified in high-cost networks.

This architecture results in virtually costless, seamless data flows across multiple blockchains.

MedianFeeds + ProofFeeds deliver a powerful balance of affordability, verifiability, and scalability — making high-quality oracle data practical even in the most expensive networks.