The creator of the Cashu ecash protocol just made Bitcoin payments look as simple as tapping your phone against someone else’s. Calle, the pseudonymous developer behind Cashu, demonstrated an NFC tap-to-pay feature on July 7 that transfers Bitcoin-backed ecash tokens between two phones, no internet connection required.
How tapping phones moves Bitcoin
Cashu is an open-source protocol that creates ecash tokens, essentially digital IOUs backed by Bitcoin or Lightning Network deposits held at entities called “mints.” You deposit Bitcoin, you get tokens on your device. Those tokens live locally on your phone, just like cash lives in your wallet.
Near-field communication, the same tech that powers Apple Pay and contactless credit cards, allows one phone to beam those ecash tokens to another phone with a simple tap. No cell signal. No Wi-Fi. No blockchain confirmation delay. Just two devices, touching briefly, and value changes hands.
Cashu uses a cryptographic technique called blind signatures, originally conceived by David Chaum in the 1980s. The mint that issues your tokens can verify they’re legitimate without knowing who spent them or where. That’s a meaningful distinction from on-chain Bitcoin transactions, which leave a permanent, traceable record on a public ledger.
