Cashu is a free and open-source Chaumian ecash protocol built for Bitcoin. Ecash is a digital bearer token that is stored on a user's device, very similar to physical cash. The Cashu protocol allows you to build applications such as wallets or voucher systems. Cashu is designed to be private, secure and scalable. Transactions are instant and nearly free.

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Cashu is a free and open-source community project with no company behind that operates any services. You can support the Cashu open-source development with a donation.

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Cashu is for Bitcoin

Cashu is tightly integrated with the Bitcoin protocol. Anyone can run a mint for their application, be it a wallet, a web paywall, paid streaming services, or a voucher and rewards system for a super market. Cashu wallets can use a mint's Lightning node for sending and receiving Bitcoin payments in exchange for ecash. This means that Cashu wallets can be used as regular Bitcoin Lightning wallets.

Ecash is cash – but electronic

Ecash was first proposed by David Chaum in 1983 as a way to make digital payments private. Cashu is a modern implementation of Chaum's ecash that uses Bitcoin for settlement. Cashu mints issue ecash tokens that can be spent by users without revealing their identity. Other Ecash projects build on the same foundation include GNU Taler and Fedimint.

Cashu applications

There are many independent implementations of the Cashu protocol which includes mints and wallets. Cashu Nutshell is the reference implementation with a command line interface (CLI). Mobile apps include eNuts, Minibits, or Macadamia. and Nutstash are Progressive Web Apps (PWAs).

The Cashu protocol

Cashu is an open ecash protocol for anyone to build on. The specifications, called Cashu NUTs (Notation, Usage, and Terminology) describe how to implement the protocol. Multiple Cashu client libaries make it easy for developers to write their own wallets.