StoneYield

StoneYield

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Contract Design

Modular smart contract architecture for secure yield generation

Contract Design

StoneYield uses a modular contract stack tuned for secure yield and clear separation of concerns: token controls, routing, and strategy execution live in distinct modules.

Architecture Overview

Core Contracts

1. StakeableAssetImpl (STUSD Token)

Built on OpenZeppelin upgradeable pieces:

  • ERC20Upgradeable – upgradeable ERC20 base
  • ERC20PermitUpgradeable – EIP-2612 approvals
  • Ownable2StepUpgradeable – two-step ownership handoff
  • PausableUpgradeable – emergency pause switch
  • ReentrancyGuardUpgradeable – reentrancy protection

2. StrategyRouter

Coordinates yield strategies:

  • Sends USDC deposits to Venus
  • Manages weights/allocations
  • Handles withdrawals from strategies
  • Owner steers configuration

3. VenuSTUSDVault

ERC-4626 compliant vault for Venus integration:

  • Deposits USDC into Venus Protocol
  • Manages vUSDC tokens
  • Tracks yield accrual
  • Provides standardized interface for router

Key Features

Token Administration (StakeableAssetImpl)

  • Soul-bound logic: _update() hook blocks transfers by default.
  • Timed locks: unlockAt timestamps per wallet.
  • Explicit unlock: Users call unlock() to lift lock when eligible.
  • Whitelist: DEX/pool addresses settable via setDex().
  • Reward minting: Admin can mint locked/placeholder STUSD via rewardMint().
  • Emergency controls: pause(), adminUnlock(), sweepUSDC().

Yield Production (StrategyRouter + VenuSTUSDVault)

  • Automated routing: USDC deposits automatically route to Venus Protocol
  • Yield optimization: Deposits earn lending interest on Venus
  • Strategy management: Owner can adjust weights and introduce new strategies
  • Transparent yields: Venus APY publicly verifiable on-chain
  • Protocol fee: 7% of Venus yields retained as protocol revenue

Events

All critical actions emit events for external tracking and transparency:

  • Deposited, Unlocked, RewardsDistributed, EarlyRedeemed
  • DexWhitelisted, TreasurySweep, SpecialAddressSet
  • StakedTokensBurned, EmergencyWithdraw

These events facilitate frontend updates, subgraph indexing, and audit logging.

Versioning and Deployment

  • Solidity version: ^0.8.28
  • Deployed on: Binance Smart Chain (BSC)
  • USDC target: BSC USDC uses 18 decimals
  • Upgradeability: StakeableAssetImpl uses transparent proxy pattern for upgradeability
  • Venus Integration: Connects to Venus Protocol's vUSDC market on BSC
  • Multisig recommended: Contract ownership should transfer to Gnosis Safe multisig for operational security

Gas and Efficiency

The contract optimizes for gas usage:

  • Batch operations available for minting and deposit (batchDepositAndMint)
  • Single ERC20 balance storage per participant
  • Lock information stored in lightweight uint40 timestamps

Yield Flow Architecture

User Deposits USDC
       ↓
StakeableAssetImpl (mints STUSD)
       ↓
StrategyRouter (routes to strategies)
       ↓
VenuSTUSDVault (deposits to Venus)
       ↓
Venus Protocol (generates yield)
       ↓
Protocol retains 7% fee
       ↓
93% of yield distributed to users

Summary

StoneYield blends soul-bound token logic with automated Venus yield routing. The modular split keeps security tight, yields transparent, and operations sustainable (7% protocol fee, ~93% to users).

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