Granola showcases decentralized order book for Cashu atomic swaps

A decentralized order book called Granola just got its first public demo, and it’s doing something genuinely novel: enabling atomic swaps between different types of ecash tokens, all without a central server, custodian, or intermediary touching the funds.

The project, built on top of the Cashu ecash protocol and coordinated through Nostr, was showcased by Cashu contributor callebtc. In its current form, Granola lets users trade between BTC-backed and USD-backed ecash in a testnet environment, with the entire system designed so that clients never relinquish custody of their tokens.

How Granola actually works

At its core, Granola is a trading layer that uses two existing Bitcoin-adjacent protocols as building blocks. Cashu provides the ecash tokens themselves, which are privacy-preserving digital bearer instruments based on Chaumian blind signatures. Nostr, the 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. A trader proposes a reserve, the counterparty accepts it, and then a quote gets locked in. The technical terms for these steps are reserve_propose, reserve_accept, and quote_lock. Each trading session generates ephemeral Nostr public keys, meaning that individual trades aren’t easily linkable to a user’s persistent identity.

The system borrows from HTLC-style mechanisms, the same hash-locked contract approach that powers Lightning Network payment channels. Shared hashes link sessions and transactions together, creating the atomic guarantee: either both sides of the trade complete, or neither does.

Orders are stored locally in the user’s browser via IndexedDB, and the platform runs balance checks before allowing orders to be posted.

Origins and current status

Granola was originally designed by developers Breno Brito (known as brenorb) and luisschwab during a hackathon in November 2024. The project has since been listed in the awesome-cashu repository, which serves as a curated directory of tools and projects built on the Cashu protocol.

The live demonstration runs entirely on testnet using fake testnut ecash, so nobody is trading real money through Granola yet. No mainnet deployment has been announced, and no token launches are associated with the project.

Why this matters for privacy-focused trading

Chaumian ecash, the cryptographic foundation underlying Cashu, was invented by David Chaum in the 1980s. It allows a mint to issue tokens that are mathematically verified as legitimate but whose specific history is unlinkable, even by the mint itself.

The main trust assumption in Cashu is that you trust the mint operator not to rug you. Granola doesn’t eliminate that trust assumption, but it does eliminate the need to trust a centralized exchange or order book operator on top of it. Every trade preserves user custody. No tokens are escrowed externally at any point during the process.

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