IOHK | Paper

Library > Kachina - Foundations of Private Smart Contracts

Kachina - Foundations of Private Smart Contracts

October/2019, Draft


Smart contracts present a uniform approach for deploying distributed computation and have become a popular means for developing security critical applications. A major barrier to adoption for many applications is the inherently public nature of existing systems, such as Ethereum. Several systems satisfying various definitions of privacy and requiring various trust assumptions have been proposed; however, none achieved the universality and uniformity that Ethereum achieved for nonprivate contracts: One framework sufficing to construct most contracts. We provide a unified security model for private smart contracts which is based on the Universal Composition (UC) model and propose a novel protocol, Kachina, for deploying privacy-preserving smart contracts, which encompasses previous systems. We demonstrate the practicality of Kachina by using it to construct a contract that implements privacypreserving payments, along the lines of Zerocash, which is provably secure in the UC setting and facilitates concurrency