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Imagine handing someone a dollar bill, except the dollar bill is Bitcoin and the handshake is two phones tapping together. That’s essentially what Cashu just pulled off.
The open-source Chaumian ecash protocol demonstrated a new NFC tap-to-pay feature on July 7, allowing users to send Bitcoin-backed ecash tokens between mobile devices without either party needing an internet connection. The sender’s side requires zero connectivity. It works on both iOS and Android using standard NFC chips already built into modern smartphones.
How tapping your phone becomes a cash transaction
The system works through bearer-style ecash tokens. These are digital tokens that function like physical cash. Whoever holds them, owns them. No account needed, no identity verification at the moment of transfer, no blockchain confirmation delay.
The tokens themselves are minted by third-party “mints” that hold actual Bitcoin or Lightning Network deposits as backing. When you want to spend, you simply tap your phone against another device. The NFC chip handles the rest, transferring the token from one wallet to another in the same way you’d tap a credit card at a coffee shop.
Calle, the protocol’s creator, showcased the feature in a demonstration that quickly reignited conversations about what digital cash could look like. The separation between token issuance and spending is the key design choice here. Because the mint creates the token in one step and the user spends it in a completely separate step, transactions can happen without on-chain fees or the usual delays associated with Bitcoin transfers.
The ecosystem building around Cashu
Several wallet and app implementations have already started integrating this NFC transfer capability. Minibits, a mobile wallet, supports Cashu token transfers. Numo, a point-of-sale application, has also been building around the protocol, meaning merchants could theoretically accept these tap-to-pay transfers in physical retail settings. Earlier work in 2025 laid the groundwork, including NFChat for NFC transfers between wallets and improved offline receiving capabilities in Nutstash, another Cashu-compatible wallet.
The protocol’s design traces its intellectual lineage directly to David Chaum’s original eCash concept from the 1980s. Chaum, widely considered the godfather of digital cash, envisioned a system where electronic payments could be as private as handing someone coins. His company DigiCash actually built this in the 1990s, but it was ahead of its time and eventually went bankrupt. Cashu essentially takes Chaum’s blueprint and wires it into Bitcoin’s infrastructure.
Funding for continued development comes partly from OpenSats, which provides long-term support for open-source Bitcoin projects.
Privacy features spark regulatory questions
Because ecash tokens are bearer instruments, they carry strong privacy guarantees. The mint that issues a token doesn’t necessarily know who ends up spending it. Transactions between users leave no on-chain trace. There’s no public ledger entry, no wallet address to monitor, no transaction graph to analyze.
The trust model deserves scrutiny, though. Cashu mints are trusted or semi-trusted entities. Users deposit Bitcoin and receive ecash tokens in return, which means you’re relying on the mint to actually hold the backing funds and honor redemptions. That’s a fundamentally different trust assumption than holding Bitcoin in your own wallet. It’s more like a bank note backed by gold reserves, which works great right up until the moment you discover the reserves aren’t there.
The practical implications for areas with limited or unreliable internet access are significant. A payment system that works offline via NFC could unlock use cases that Lightning alone cannot reach.
Disclosure: This article was edited by Editorial Team. For more information on how we create and review content, see our Editorial Policy.
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