NuCypher is a decentralized Key Management System (KMS) that addresses the limitations of using consensus networks to securely store and manipulate private, encrypted data. It provides encryption and cryptographic access control, performed by a decentralized network, leveraging proxy re-encryption. Unlike centralized KMS as a service solutions, it doesn’t require trusting a service provider. NuCypher enables sharing of sensitive data for both decentralized and centralized applications, providing security infrastructure for applications from healthcare to identity management to decentralized content marketplaces. NuCypher will be an essential part of decentralized applications, just as SSL/TLS is an essential part of every secure web application.