Penumbra is a private-by-default proof-of-stake network. Penumbra provides private transactions in any kind of cryptoasset, using Inter-Blockchain Communication (IBC) to connect to other chains. It also has a novel staking mechanism that provides accountability for validators but privacy for delegators, allowing them to privately stake, earn rewards, and participate in governance. Finally, Penumbra provides ZSwap, a decentralized exchange integrated with its shielded pool. ZSwap provides sealed-bid batch auctions on the market-taker side and Uniswap-v3-style concentrated liquidity on the market-maker side. Sealed-bid batch auctions prevent frontrunning, provide better execution, and reveal only the net flow across a pair of assets in each block, and liquidity positions are created anonymously, allowing traders to approximate their desired trading function without revealing their individual beliefs about prices.