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Oracle System Architecture

Overview

The ACBU oracle system provides reliable, tamper-resistant price feeds for all basket currencies by aggregating multiple independent sources.

Multi-Source Price Feeds

Price Discovery Layers

Layer 1: Central Bank Official Rates

  • Source: Each country's central bank
  • Update: Daily (some real-time)
  • Weight: 40% of final rate
  • Characteristics: Most authoritative but sometimes delayed

Layer 2: Fintech Partner Transaction Rates

  • Source: Flutterwave, Paystack, etc. actual transactions
  • Update: Real-time
  • Weight: 40% of final rate
  • Characteristics: Reflects real market rates users experience

Layer 3: Forex Market Rates

  • Source: Oanda, XE, Bloomberg
  • Update: Real-time
  • Weight: 20% of final rate
  • Characteristics: International market perspective

Aggregation Method

  • Median of all three sources
  • Outlier detection: If one source deviates >3%, flag for review
  • Fallback hierarchy: If one source fails, use remaining two

Technical Implementation

Smart Contract Oracle System

On Stellar:

  • Multi-sig oracle contract (5 validators)
  • Each validator pulls from different sources
  • Consensus mechanism: Median of 5 feeds
  • Update frequency: Every 6 hours
  • Emergency update: If any currency moves >5%

Oracle Validators

  • 2 nodes: Internal technical team
  • 2 nodes: Independent third party (Chainlink-style)
  • 1 node: Fintech partner validator
  • Requirement: All nodes must sign for rate to be accepted

On-Chain Price Feed Format

{
  "timestamp": "2026-01-08T12:00:00Z",
  "rates": {
    "NGN_USD": 0.000645,
    "ZAR_USD": 0.0547,
    "KES_USD": 0.0073,
    ...
  },
  "signatures": ["0x...", "0x...", "0x...", "0x...", "0x..."]
}

Oracle Security Measures

Protection Against Manipulation

1. Deviation Limits

  • Max 5% change per 6-hour update
  • If larger move detected: require 3/5 oracle consensus
  • Pause minting/redemption if >10% unexplained deviation

2. Multiple Source Validation

  • If sources disagree by >3%: trigger review
  • Human oversight for anomalies
  • Ability to pause oracle updates

3. Time-Weighted Average

  • Use 24-hour TWAP for redemptions (smooth volatility)
  • Use spot rates for display purposes
  • Prevents flash crash exploitation

4. Circuit Breakers

  • If any currency shows extreme volatility:
    • Temporarily use 48-hour average
    • Notify users of heightened volatility

Update Frequency

  • Standard: Every 6 hours
  • Emergency: If any rate moves >5%
  • Smart Contract Updates: Every 6 hours on weight and oracle
  • API Access: Real-time for partners

Price Feed Sources by Currency

NGN (Nigerian Naira)

  • Central Bank: CBN official rates
  • Fintech: Flutterwave real-time rates
  • Forex: Oanda, XE, Bloomberg

KES (Kenyan Shilling)

  • Central Bank: CBK official rates
  • Fintech: Flutterwave, Chipper Cash rates
  • Forex: Oanda, XE, Bloomberg

RWF (Rwandan Franc)

  • Central Bank: BNR official rates
  • Fintech: Flutterwave, MTN MoMo rates
  • Forex: Oanda, XE, Bloomberg

(Similar structure for all 10 currencies)

Oracle Reliability

Redundancy

  • Multiple validators prevent single point of failure
  • Multiple data sources ensure accuracy
  • Fallback mechanisms for source failures

Monitoring

  • Real-time health checks on all validators
  • Alert system for anomalies
  • Automatic failover to backup sources

Transparency

  • All price feeds published on-chain
  • Public dashboard showing current rates
  • Historical rate data available

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