Oracle Design для TON DeFi

Проблема: блокчейн не знает внешних цен

Smart contracts не имеют доступа к внешнему миру — они не могут вызвать API биржи для получения цены. Oracle — это механизм доставки off-chain данных on-chain.

Push vs Pull Oracle Models

Oracle Models: Push vs Pull

Push Oracle

Pull Oracle (RedStone)

TWAP Oracle (Time-Weighted Average Price)

DEX pools естественно являются TWAP oracle-ами:

TWAP calculation:
  Записывать cumulative_price каждый блок:
    cumulative += current_price × time_elapsed
  
  TWAP за период [t1, t2]:
    twap = (cumulative[t2] - cumulative[t1]) / (t2 - t1)

Benefit: resistant to flash manipulation
  (невозможно мгновенно изменить TWAP — нужно удерживать price долго)

Oracle Design для Lending Protocol

Lending Oracle Requirements:
1. Price freshness: < 60 seconds staleness
2. Price accuracy: < 0.5% deviation from market
3. Redundancy: multiple sources
4. Manipulation resistance: TWAP or multi-source median
5. Fallback: if oracle fails → pause protocol (not use stale data)

Multi-source Aggregation Pattern

Oracle Aggregator Contract:

Sources:
  - Pyth Network (off-chain signed data)
  - STON.fi TWAP (on-chain DEX price)
  - DeDust TWAP (on-chain DEX price)

Aggregation:
  1. Collect prices from all sources
  2. Reject outliers (> 5% from median)
  3. Final price = median of remaining
  4. Store with timestamp
  
Staleness check:
  if (now() - last_update > MAX_STALENESS) → reject price

Security Considerations

Attack	Description	Mitigation
Price manipulation	Attacker moves DEX price → triggers unfair liquidation	TWAP (time-averaged), multi-source
Oracle downtime	Oracle stops updating → stale prices	Staleness check, fallback oracle, protocol pause
Front-running	Attacker sees oracle update tx → trades before it	Commit-reveal, pull oracle
Flash loan + oracle	Manipulate pool → distort TWAP	Не применимо на TON (no flash loans)

TIP

TON advantage: no flash loan oracle attacks

На Ethereum flash loan attacks на TWAP oracle — major threat. На TON flash loans невозможны → TWAP oracle-ы значительно безопаснее. Это делает on-chain DEX TWAP viable первичным source для lending oracle.

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