Cowrie Research

krux-primary-sources-2026-05-01

4 min read

Krux primary-source snapshot

Fetched: 2026-05-01 UTC

1) Official docs homepage

Source: https://selfcustody.github.io/krux/

Selected excerpts from the official docs:

Krux is an open-source firmware that transforms off-the-shelf Kendryte K210 devices … into versatile bitcoin transaction signers.

Interacting seamlessly with leading coordinator wallets through QR codes, SD cards, and even thermal printers, the user-friendly firmware offers unique features to support transactions and mnemonic backups in an offline environment.

Additional signals from the source:

  • The docs homepage is the clearest top-level source for categorizing Krux as firmware for commodity signer hardware rather than as a single branded device
  • It also shows that backup tooling and offline operational workflows are core to the project, not just transaction signing

2) Getting started docs

Source: https://selfcustody.github.io/krux/getting-started/

Selected excerpts from the official docs:

Krux is open-source Bitcoin signing firmware for devices with the K210 chipset; also known as a hardware signer.

Signing operations in Krux are done offline via QR code or via SD card using the PSBT functionality.

Krux runs offline, and therefore never handles the broadcasting part of the PSBT transaction.

Additional signals from the source:

  • This page is one of the most important categorization sources because it makes the airgapped operational model explicit
  • The same page lists compatible coordinator wallets including Sparrow, Specter Desktop, Liana, Bitcoin Safe, Nunchuk, BlueWallet, Bitcoin Keeper, and BULL Wallet, while also noting Electrum incompatibility
  • The coordinator-wallet framing makes Krux look like signer infrastructure layered into a broader Bitcoin wallet stack rather than a closed wallet ecosystem

3) Devices and parts list

Source: https://selfcustody.github.io/krux/parts/

Selected excerpts/signals from the official docs:

  • The comparative table lists supported devices such as M5StickV, Maix Amigo, Maix Dock, Yahboom, Maix Cube, WonderMV, TZT, and Embed Fire
  • The same table provides price ranges, screen sizes, camera details, battery presence, assembly requirements, and warnings for each board
  • All supported devices are framed as Kendryte K210-based hardware, which is a strong signal that the project’s hardware philosophy is commodity-board reuse rather than a custom appliance model

Additional signals from the source:

  • This page is especially useful because it reveals Krux’s practical deployment model: users can choose between near-plug-and-play boards and more DIY builds with rotary encoders, cases, or soldering
  • The parts page is one of the best primary sources for understanding Krux as a low-cost signer platform rather than just a firmware repo

4) GitHub README

Source: https://raw.githubusercontent.com/selfcustody/krux/main/README.md

Selected excerpts from the official repo:

Krux is an open-source firmware facilitating the creation of Bitcoin signing devices from readily available components.

This software has not yet been formally audited by a third party. Use at your own risk!

Additional signals from the source:

  • The README confirms the commodity-hardware and airgapped-signing model in first-party technical docs, not only in marketing copy
  • It also documents installer and release flows, build-from-source instructions, dependency structure, testing, linting, and simulator usage, which shows Krux has a real contributor surface
  • The unaudited warning is a high-signal operational caveat that should stay attached to the project summary

5) Simulator and developer surface

Source: https://raw.githubusercontent.com/selfcustody/krux/main/README.md

Selected excerpts/signals from the official repo:

  • The README documents a simulator for multiple device types, screenshot-generation flows for docs, and Linux/Mac/Windows-oriented flashing and debugging paths
  • It also references the Krux installer and the use of Docker / Poetry / pytest / lint tooling, reinforcing that this is a living firmware-development project rather than a static binary drop

Additional signals from the source:

  • The simulator makes Krux unusually accessible for research because people can inspect the UX before sourcing hardware
  • This further supports cataloging Krux as signer firmware infrastructure with a meaningful public engineering surface

Notes

  • Krux appears best cataloged as bitcoin signing-firmware infrastructure / DIY self-custody signer platform / airgapped QR-and-SD workflow / mnemonic-backup tooling.
  • No canonical standalone whitepaper or litepaper surfaced in this pass.
  • The most useful primary sources are the docs homepage, getting-started and parts pages, and the public GitHub README.

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