The Composability Problem in DeFi Lending An ideal DeFi use case for exploring the composability problem is Overcollateralized Lending Markets (such as Aave or Compound). In a standard public-ledger implementation, these markets force total transparency: every user's wallet address, deposited collateral balance, borrowed amount, and exact health factor are broadcasted in plaintext on-chain. What Information to Keep Confidential To protect users and institutions from predatory behavior without breaking the system, we need to keep specific state variables hidden: Individual Position Sizes & Balances: The exact amount of collateral a user deposits and the amount they borrow should be encrypted. Exact Health Factors: The real-time liquidation threshold metric ($Health\ Factor = \frac{Collateral \times Liquidation\ Threshold}{Total\ Debt}$) must remain private so that third-party bots cannot build targeted "hit lists" to ruthlessly front-run liquidations. Preserving Composability via Fully Homomorphic Encryption (FHE) The core tension of "The Composability Problem" is that hiding data usually breaks the ability of other smart contracts to interact with it. If a lending pool's data is hidden behind a zero-knowledge proof or siloed in a private enclave, another protocol cannot easily read it to execute flash loans, assess risk, or compose complex yield strategies. By utilizing Fully Homomorphic Encryption (FHE)—the cryptographic primitive pioneered by @fhenix—we can solve this paradox: Encrypted State, Public Logic: Smart contracts can execute math directly on ciphertexts without decrypting them. Safe Liquidation Execution: A lending contract can evaluate whether a user's hidden health factor has crossed a critical threshold (e.g., checking if $Health\ Factor < 1$) and execute a liquidation routine entirely on-chain. The system knows that a position is underwater and allows liquidators to interact with it, without ever exposing who holds the position or the exact scale of the capital involved. Maintaining Interoperability: Because FHE smart contracts operate natively within a shared state environment, other DeFi primitives (like automated portfolio managers or credit scoring protocols) can still securely compose with these encrypted lending pools using permissioned access controls—unlocking institutional-grade privacy without sacrificing decentralization or composability. @fhenix