Due to the permissionless and feeless nature of the deposit() and withdraw() methods, everyone can use them to swap whitelisted USDC-like tokens for free. This might be especially attractive (for arbitraging) if such a stablecoin slightly depegs.  
Users cannot expect to be able to withdraw the same stablecoin theyve deposited since its underlying balance might be depleted.
Restrict the deposit() method to only be callable from the asdRouter contract.
