Granola, a decentralized order book built on the Cashu ecash protocol, has completed its first public demonstration. The platform enables atomic swaps between different types of ecash tokens—such as BTC-backed and USD-backed variants—without requiring a central server, custodian, or intermediary to hold funds.
The project was showcased by Cashu contributor callebtc and currently operates on testnet. Unlike traditional exchanges, Granola ensures that users maintain custody of their tokens throughout the trading process.
Technical Architecture
Granola combines two existing protocols to create its trading layer. Cashu provides the ecash tokens themselves, which are privacy-preserving digital bearer instruments based on Chaumian blind signatures. Nostr, a decentralized social protocol, handles both the public broadcasting of orders and private coordination between trading parties.
The settlement process follows a structured three-message protocol: reserve_propose, reserve_accept, and quote_lock. Each trading session generates ephemeral Nostr public keys, meaning individual trades are not easily linkable to a user's persistent identity.
The system uses hash-locked contracts similar to those powering Lightning Network payment channels, creating an atomic guarantee where both sides of a trade either complete together or neither completes. Orders are stored locally in the user's browser via IndexedDB, with balance checks performed before orders are posted.
Development and Status
Granola was designed by developers Breno Brito (brenorb) and luisschwab during a hackathon in November 2024. The project has since been listed in the awesome-cashu repository, a curated directory of Cashu-based tools and projects.
The current demonstration runs entirely on testnet using test ecash tokens. No mainnet deployment has been announced, and no tokens are associated with the project.
Privacy Implications
Chaumian ecash, the cryptographic foundation of Cashu, was invented by David Chaum in the 1980s. It allows a mint to issue verified tokens whose transaction history is unlinkable, even to the mint operator.
While Granola does not eliminate the trust assumption that users must place in mint operators, it removes the need to trust a centralized exchange or order book operator. Users maintain custody of their tokens throughout the trading process, with no external escrow required.
