The Best Bitcoin Hardware Wallets & Seed Phrase Backup Tools
A simple directory of the best Bitcoin signing devices, metal seed backup tools, and supporting wallet software — because your sats are best stored cold.
Krux
Open-source Bitcoin signing device firmware for Kendryte K210 hardware. DIY, air-gapped via QR codes and SD card. Free firmware.
Krux is open-source firmware that transforms off-the-shelf Kendryte K210 devices — such as the Maix Amigo, M5StickV, Yahboom, WonderMV, and others — into fully functional, air-gapped Bitcoin transaction signing devices. It supports mnemonic creation and recovery, BIP-39 passphrase (word 25), BIP85 child seed derivation, single-sig and multisig wallets, and QR code or SD card transaction signing. Optional thermal printer support enables paper backups. Krux runs entirely offline and supports empirical entropy measurement for seed generation. Compatible devices with large touchscreens cost roughly $50–100 USD. The firmware is free and fully open source on GitHub. Note: not yet formally third-party audited.
