Tapsigner: Smart NFC Bitcoin Card

Description

Tapsigner is a smart NFC card that allows you to sign bitcoin transactions by tapping it on your phone. The majority of the wallet functionality is provided by your mobile wallet, while Tapsigner maintains the secrets. By keeping your keys separate from your wallet, the card functions like a hardware wallet that fits inside your ordinary pocket wallet. Its lower cost is intended to make hardware wallet functionality and security available to a broader global market. The card is made by the bitcoin company Coinkite.

Although hardware wallets are more secure than mobile wallets, they are more difficult to use and move. Tapsigner seeks to bridge the usability and transportability gap between mobile wallets and hardware wallets. Tapsigner is the size of a credit card and can be used by simply tapping it on your phone.

How Tapsigner works

Tapsigner requires you to have a mobile wallet. For the time being, the card is only compatible with Nunchuk and Hexa wallets. The card does not come with any private keys. Instead, it uses Bitcoin cryptography library to generate keys with the help of a compatible mobile wallet before you first use it.

To use the card with a computer, you need a USB NFC card reader and the cktap command-line software or any desktop wallet that uses Tapsigner open protocol. The private key is generated within the card and never leaves it, regardless of any malware or keyloggers that may be present on a connected computer.

The card generates private keys that follow the BIP 32 standard rather than the BIP 39 standard. This essentially means that you cannot use it with a seedphrase. You will need an encrypted copy of your private keys to back up your private keys.

It comes with an RF (radio frequency) blocking sleeve to prevent unauthorized access by RF readers with malicious intent. The card must be completely inserted into the sleeve because even a 5 mm gap can allow a reader to pick up a signal.

Features

• Verifiable entropy assures you that only the Tapsigner has access to the private key that governs bitcoin.
• It can be easily and securely backed-up into a file.

Tapsigner use cases

• Message signing
• Phone wallet cosigning
• Opening and closing Lightning Network channels
• App authentication
• Collaborative multisig service applications
• Using a NFC with a Lightning Network node
• Partially signed Bitcoin transactions (PSBTs) via HWI

More information

• Tapsigner FAQ