Decentralized finance (DeFi) lending traditionally relies on overcollateralization to mitigate the risks associated with pseudoanonymous users, but this approach limits capital efficiency. The development of undercollateralized lending protocols, enabled by technological advances like the DECO privacy-preserving oracle protocol, offers a promising solution by allowing reliable assessment of borrowers' creditworthiness without compromising data privacy. DECO, developed at Cornell University and acquired by Chainlink, uses zero-knowledge proofs to verify off-chain data, enabling secure and private undercollateralized loans. A proof of concept with Teller and Chainlink Labs demonstrated DECO's potential to lower collateral requirements by proving users' bank balances without exposing sensitive information. This innovation could significantly expand the DeFi market by integrating a vast amount of economic value while maintaining user privacy and fostering more efficient lending practices.