Scope

1. EVM smart contract design
2. Contract is upgradeable, but scope does not include subsequent upgrades
3. Assist with frontend integration
4. Audit will be handled by SOON team
5. Due date: 2025/05/22

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1. Overview

$CASH is a decentralized yield-bearing stablecoin designed to provide a stable cryptocurrency investment option and generate yields through CASH staking.

Its core features include:

• Accept multiple stablecoin deposits:
  • USDe (Ethena Labs)
  • USD0 (Usual Money)
  • mUSD (Manta Network)
  • lvlUSD (Level-money)
• Issue $CASH: An ERC-20 token pegged 1:1 to USD, instantly redeemable for USD0, lvlUSD, mUSD, USDe.
• Stake $CASH to receive $sCASH: Users can stake CASH to receive sCASH, which provides yield. Unstaking requires a 7-day cooling period. Yields come from staking equivalent underlying stablecoins (weighted APY minus 1%). </aside>

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2. Objectives

• Stability: Maintain CASH's 1:1 USD peg through full collateral management and price monitoring.
• Yield Generation: Generate yields by staking CASH to receive sCASH, providing returns from equivalent underlying stablecoin staking (minus 1%) and 0.5% from sCASH staking. </aside>

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3. Functional Requirements

3.1 Stablecoin Acceptance

• Supported Stablecoins:
  • USDe (Ethena Labs)
  • USD0 (Usual Money)
  • mUSD (Manta Network)
  • lvlUSD (Level-money )
• Deposit Mechanism:
  • Users deposit supported stablecoins into the Vault.
  • Contract mints CASH at a 1:1 ratio based on the USD value of deposited stablecoins (e.g., deposit 100 USDe, mint 100 sCASH).
• Validation:
  • Verify deposited stablecoin contract addresses and balances match whitelist.
• Future Expansion:
  • First version supports fixed stablecoins listed above, future additions possible through contract upgrades.

3.2 CASH Issuance

• Token Standard: CASH is an ERC-20 token pegged 1:1 to USD.
• Minting:
  • Contract mints equivalent CASH when users deposit supported stablecoins.
• Burning and Instant Redemption:
  • Users can instantly redeem CASH for USD0, lvlUSD, mUSD, USDe if sufficient reserves exist in the Vault.
  • During redemption, contract burns corresponding CASH and returns equivalent stablecoins.
• Peg Maintenance:
  • Collateral fully backed by deposited stablecoins, total supply synchronized with collateral value.

3.3 sCASH Staking Mechanism

• Staking Process:
  • Users can stake CASH to receive equivalent sCASH (e.g., stake 1000 CASH to receive 1000 sCASH).
  • sCASH is the staked version of CASH, yield returns for holders.
• Underlying Stablecoin Staking:
  • When users stake CASH, protocol stakes equivalent stablecoins (USD0, lvlUSD, mUSD, USDe) in respective protocols to earn yield.
  • Staking Protocols:
    • USDe: Staked with Ethena Labs, receiving sUSDe, estimated 5% APY.
    • USD0: Staked with Usual Money, estimated 12% APY.
    • mUSD: Staked with Manta Network, APY TBD.
    • lvlUSD: Staked with Level Finance, receiving slvlUSD, estimated 8.48% APY.
• Unstaking:
  • Unstaking sCASH requires 7-day cooling period, after which users receive CASH plus accumulated yields.
• Yield Calculation:

  • sCASH yields come from weighted average APY of underlying stablecoin staking minus 1%.

  • Weighted APY Formula: where represents each stablecoin (USDe, USD0, etc.).

    WeightedAPY = ∑(StablecoinAPYi×DepositProportioni)

  • Example: If underlying weighted APY is 8%, sCASH APY is 7%.

• Yield Distribution:
  • sCASH value appreciates over time, reflecting underlying yields.
  • Users receive original CASH plus accumulated yields (as additional CASH) upon unstaking.
  • Distribution frequency: Daily or weekly, per protocol settings.
• Treasury Vault:
  • Function: Stores protocol earnings, including 1% yield deduction.
  • Transparency: Balance and transaction records public on-chain, dashboard displays fund flows.

3.4 Withdrawal and Liquidity Management

• Withdrawal Process:
  • Users can burn CASH for instant redemption of USD0, lvlUSD, mUSD, USDe.
  • If Vault reserves are insufficient, protocol can partner with external liquidity providers or provide DEX liquidity.
• sCASH Unstaking:
  • Unstaking requires 7-day cooling period, after which CASH and yields are returned.
• Liquidity Reserves:
  • Protocol maintains unstaked stablecoin reserves (recommended 5%-20%), adjusted based on 30-day withdrawal data.

3.5 Stablecoin Exchange Mechanism (Swap Mathematics)

CASH's exchange mechanism uses a StableSwap algorithm similar to Curve Finance, ensuring low slippage and stable exchange rates. Core formula:

∑ixi+Dn+1An∏ixi=ADn+Dn+1n

Where:

• (xi): Quantity of each stablecoin (i)
• (D): Total quantity when all stablecoins are equal in price
• (A): Amplification coefficient (leverage), optimal value 85
• (n): Number of stablecoins

3.6 Security and Transparency

• Security Measures:
• Transparency: </aside>

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