> For the complete documentation index, see [llms.txt](https://docs.yolkfi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.yolkfi.com/02.-technical-architecture/security-and-storage.md).

# Security Model & Storage Optimization

### Comprehensive Threat Model

* **Host-Enforced Reentrancy Protection:** Soroban’s host environment prohibits recursive contract reentrancy by default. If Contract A calls Contract B, and Contract B attempts to re-enter Contract A while active on the call stack, the host immediately aborts the call.
* **Integer Overflow & Arithmetic Safety:** All contracts compile with `overflow-checks = true` in the Cargo release profile. Any overflow/underflow automatically panics and reverts the transaction. Financial accounting functions utilize checked arithmetic (`checked_add`, `checked_mul`).
* **Front-Running Immunity:** Yield distributions are derived directly from signed Oracle submissions, eliminating MEV and front-running vulnerabilities.
* **Replay Attack Defense:** Every production report carries a distinct `cycle_id` that is permanently committed to persistent storage. Duplicate submission attempts are atomically rejected.
* **Multisig Governance & Key Rotation:** Treasury administrative functions require multi-signature authorization. Oracle keys can be rotated dynamically via admin controls on `YieldDistributor.rs` without contract redeployment.

***

### Contract Upgradeability & Protocol 28 Evolution

YolkFi implements a transparent, auditable upgrade pattern adhering to Stellar community standard **SEP-0049**:

1. **Protocol 28 Preparedness:** The contract architecture is structured to leverage upcoming **Protocol 28** features, specifically **CAP-85 (Atomic Upgrades for Contract Fleets)** and **CAP-86 (Data Migrations)** for zero-downtime state upgrades.
2. **Multisig Upgrade Gates:** Upgrades are executed via `env.deployer().update_current_contract_wasm()` and require M-of-N threshold signatures from the protocol multisig account.
3. **Decentralization Roadmap:** As the protocol expands to multiple farm partners, upgrade authorities transition toward timelocked governance and eventual contract immutability for core accounting logic.

***

### Storage Optimization & Proactive TTL Extension

Soroban utilizes a state archival system with Time-To-Live (TTL) ledgers. YolkFi implements a proactive strategy to eliminate archival risk:

```rust
// 1. Instance Storage Extension (performed during contract calls)
env.storage().instance().extend_ttl(500_000, 1_000_000);

// 2. Persistent Storage Extension (per key during NFT transfer or yield claim)
env.storage().persistent().extend_ttl(&key, 500_000, 1_000_000);
```

* **Instance Storage:** Admin addresses, authorized Oracle signer sets, and contract configuration.
* **Persistent Storage:** Investor eligibility records, Hen NFT ownership maps, and distribution history.
* **External Cron Bumps:** A background relayer broadcasts `ExtendFootprintTTLOp` transactions to ensure inactive records never lapse.


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