Add Satochip NFC Hardware wallet support

[Toporin]

This is a pull request to add support for the Satochip hardware wallet.

The Satochip hardware wallet is based on a jacavard smartcard and is fully open-source.
The firmware uses a javacard applet that is loaded on the smartcard.
With native NFC (Near Field Communication) support, Satochip enables seamless interaction with mobile devices.

Satochip technical details

• Platform: JavaCard 3.0.1-compliant smartcard with an EAL6+ secure element.
• Key management: supports BIP39 seeds; private keys are derived and stored within the secure chip, never exposed externally.
• NFC support: contactless communication via NFC, compatible with Android and iOS devices equipped with NFC readers.
• Cryptographic capabilities: implements ALG_ECDSA_SHA_256 for Bitcoin signatures and optional Schnorr signature support (beta v0.14+) for Taproot and Nostr.

Advantages of Satochip

Here are the main advantages of the Satochip hardware wallet:

• Security: private keys remain offline in a tamper-resistant chip, protected by a PIN code.
• Mobile-friendly: NFC support for quick, contactless interaction with mobile devices.
• Affordable: priced at approximately €25, Satochip offers a budget-friendly alternative.
• Open-source: javacard applet is AGPLv3.
• DIY: build a hardware wallet in a few minutes using widely available blank smartcards.
• Portability: credit card-sized form factor is discreet, easy to carry, and durable.
• Compatibility: with widely-used client Sparrow for Desktop use.

NFC Support

Hardware wallets have become the gold standard for securing Bitcoin, but they often lack mobile-friendliness, making everyday transactions cumbersome. NFC technology can bridge this gap and improve Bitcoin adoption by enhancing convenience without compromising security.

There are a few players in the Bitcoin hardware wallet NFC field such as:

• Satochip — one of the pioneer in this segment;
• TapSigner from Coinkite;
• TwentyTwo — the very first to implement a large self-powered screen.

We tried to implement NFC integration in a simple and flexible way, making it easy to support additional NFC devices in the future. We are available to collaborate and ensure a smooth integration process while aligning with your standards. We are happy to discuss any aspects of the implementation, including UI considerations, integration details, or potential modifications, to make sure this solution fits seamlessly into Green Wallet. We can also provide samples for testing. Let us know how we can assist!

More info:
https://github.com/Toporin/ (Official repository)
https://x.com/satochip (X account)
https://t.me/Satochip (Telegram support)

[Toporin]

Satochip integration screenshots:

[Bastien-Satochip]

Video context - easy to setup:

Satochip x Green Wallet - Pair the hardware wallet over NFC
https://github.com/user-attachments/assets/cb8b5454-73c1-4350-a03b-c9590f49c610

Satochip x Green Wallet - Sign a transaction over NFC
https://github.com/user-attachments/assets/0cb8f194-f782-4869-993c-2efbc76988b8

[domegabri]

@Bastien-Satochip can you set us up with some devices so we can test too?

[Bastien-Satochip]

Hey 👋  Yeah sure of course!  How can I reach you?

[domegabri]

Hey 👋 Yeah sure of course! How can I reach you?

[email protected]

[Bastien-Satochip]

Hey 👋 Yeah sure of course! How can I reach you?

[email protected]

Mail sent. Thank you!

[Toporin]

FYI, we have added support for Liquid-Bitcoin in Satochip latest beta firmware, and updated the pull request.

[domegabri]

@Toporin we are undergoing a large refactoring of the UI, we won't be able to test this properly for a bit. I will keep you up to date on our progress so that you can rebase your implementation once we are done

[Bastien-Satochip]

@domegabri : did you receive my mail?