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README.md

Oracles on Stellar

This guide covers oracle solutions for bringing off-chain data to Stellar/Soroban smart contracts.

Overview

Oracles provide external data (prices, events, etc.) to smart contracts. On Stellar, the primary oracle solution is Reflector Network, with additional options like DIA.

Why Use an Oracle?

Smart contracts can't access external data directly. Oracles bridge this gap for:

  • Price feeds - Token prices for DeFi protocols
  • Random numbers - Gaming and lottery applications
  • External events - Real-world data triggers
  • Cross-chain data - Information from other blockchains

Oracle Providers

Reflector Network

The primary community-powered price oracle for Stellar, implementing SEP-40.

Feature Details
Website reflector.network
Docs Stellar Oracle Providers
Standard SEP-40 compatible

Features:

  • On-chain and off-chain price data
  • Webhook notifications
  • Community-operated nodes
  • Multiple asset support

Integrations:

  • Blend Protocol
  • Orbit CDP
  • DeFindex
  • Laina
  • EquitX
  • Slender

DIA Oracle

Cross-chain oracle with extensive asset coverage.

Feature Details
Website diadata.org
Blog DIA on Soroban
Assets 20,000+ supported

Features:

  • VWAPIR pricing methodology
  • Custom feed configuration
  • Cross-chain compatibility
  • Enterprise support

Using Oracles in Contracts

Reading Price Data (SEP-40)

use soroban_sdk::{contract, contractimpl, Address, Env};

#[contract]
pub struct MyContract;

#[contractimpl]
impl MyContract {
    pub fn get_price(e: &Env, oracle: Address, asset: Address) -> i128 {
        // Call oracle contract to get price
        let price: i128 = e.invoke_contract(
            &oracle,
            &Symbol::new(e, "lastprice"),
            vec![&e, asset.into_val(e)],
        );
        price
    }
}

Price Feed Structure

SEP-40 oracles typically return:

pub struct PriceData {
    pub price: i128,      // Price in base units
    pub timestamp: u64,   // Unix timestamp
}

Best Practices

  1. Use multiple sources - Cross-reference prices when possible
  2. Check staleness - Verify timestamp is recent
  3. Handle failures - Gracefully handle oracle unavailability
  4. Set boundaries - Reject prices outside reasonable ranges
  5. Consider latency - Account for block time in time-sensitive operations

Security Considerations

  • Oracle manipulation - Be aware of flash loan attacks
  • Stale data - Always check price freshness
  • Single point of failure - Consider decentralized oracles
  • Price deviation - Implement circuit breakers for large swings

Resources