Cashu has introduced an experimental card featuring a JavaCard chip for making offline payments with Bitcoin-backed ecash. Tokens are loaded onto the card and transferred during a contactless payment before being settled later with the issuing mint. The card provides 128 storage slots, binds tokens to a key that never leaves the chip and uses a single signature to prevent double spending. It relies on a draft specification, NUT-CCP, and requires users to manually install an open-source application onto an NXP J3R180 card sold for about $9. Cashu nevertheless highlights the permanent loss of funds if the card is lost, reliance on the mint’s solvency and merchants’ exposure to double spending until final settlement.
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