Strata PreDeposit Vaults

Summary

In this audit, we reviewed the Pre-Deposit Vaults for Strata's upcoming point incentive program. This program is divided into two phases, the point phase and the yield phase. During the initial point phase, users are able to deposit either USDe directly or a whitelisted share token that is backed 1:1 by USDe. Upon deposit, the client accrues off-chain points, which serve as the basis for future rewards under the project’s incentive framework. In exchange for their deposit, the client receives pUSDe, a vault share token representing their position within the system. When the owner transitions the vault into the yield phase, all whitelisted share tokens are converted into USDe. These converted assets, along with any originally deposited USDe, are collectively staked to obtain sUSDe, a yield-bearing representation of USDe linked to Ethena's staking mechanism. From this point onwards, users may now continue to deposit USDe, which is immediately staked into sUSDe, or provide sUSDe directly to the vault. Users holding pUSDe can continue to earn off-chain points; however, these positions do not accrue any staking rewards, even though technically, their initial deposit got staked and is accuring rewards. By choosing to remain in the pUSDe vault, the client forfeits the yield generated through staking in favor of accumulating off-chain points. When a user redeems their pUSDe, they do not receive USDe back (the original underlying token) but are instead provided an equivalent value of their USDe denominated deposit, now denominated in sUSDe. For example, if a client had originally deposited 1 USDe, they would receive approximately 0.833 sUSDe upon redemption, assuming sUSDe has appreciated due to accrued staking rewards. Alternatively, clients may deposit their pUSDe into the yUSDe vault. While this action disqualifies them from receiving further off-chain points for those pUSDe holdings, it essentially grants access to the entire pUSDe vault’s yield accumulating in the yield phase by its sUSDe holdings. So users can choose between two strategies, namely farming for the off-chain points while holding pUSDe shares and forfeiting the yield or benefitting from the boosted sUSDe rewards by holding yUSDe shares but not accruing any off-chain points. Overall, we only identified minor aspects as part of this review. While the code is in good shape, the chosen inheritance structure of the contracts reduces code readability. Furthermore, the test suite could be expanded and the failing tests could be adjusted. **Fix Review Update** All issues have been fixed or reasonably acknowledged.