SeedSigner proved you can build a serious signer from cheap parts. Krux pushes the same idea one step further: it is not a device at all, but open-source firmware you flash onto ordinary, off-the-shelf gadgets, turning a generic touchscreen toy into a Bitcoin-only, air-gapped signing device.
Pick a Device, Any Device
Krux runs on a family of inexpensive K210-based boards sold for entirely unrelated purposes: the Maix Amigo (a full touchscreen unit, the most comfortable pick), the tiny M5StickV, and several others, mostly in the $30 to $80 range. That has the same supply-chain benefit we praised for SeedSigner: nobody tampers with a shipment of generic maker gadgets, because nobody knows they are destined to become wallets. No soldering, no assembly. Flash the firmware and the gadget changes careers.
Air-Gapped, Three Ways
Krux never connects to your computer for signing. Transactions move as PSBTs by QR code (camera in, screen out), by microSD card for wallets that prefer files, and, for the fun of it, backups and addresses can even go to a cheap thermal printer. It pairs with the coordinators we already use: Sparrow on the desktop, and Liana as well, which we will get to, because that pairing is Krux's ace.
Seeds on Your Terms
Krux is built for people who like doing things themselves. It generates seeds from your own dice rolls or camera entropy, exactly in the spirit of our DIY seed guide. By default a seed is loaded for the session and gone when the power is; if you want convenience, Krux can store your mnemonic encrypted on the device or an SD card, unlocked by a key you choose, a middle path between SeedSigner's strict statelessness and a conventional stored-key device. Backups are flexible too: classic words on metal, compact SeedQR codes, or punches on a TinySeed plate, with the usual rule unchanged: whatever the format, verify the backup before it guards real money.
The Ace: Miniscript
Since early 2025, Krux supports Miniscript, including Taproot Miniscript. In plain terms: Krux can read a wallet descriptor, show you the spending policy in a readable form, and sign for timelocked setups. That makes it one of the few DIY signers that works with Liana's recovery paths, over QR or fully by SD card. If you want Liana's lost-key insurance without buying from a hardware vendor, a Krux build is the DIY road there. It handles ordinary single-sig and multisig just as happily.
Getting Started
The path is the standard one from our signing device guide: buy a supported board from any electronics seller, download the firmware from the official project only, verify it, flash it over USB once, and from then on updates can arrive by SD card with signatures checked on the device itself. Load or create a seed, pair with your coordinator by QR, receive a test amount, verify the address on Krux's own screen, and do a recovery dry run before trusting it with savings.
The usual rules hold. Verify the firmware before flashing, verify addresses on the device screen, and treat your seed backup as the wallet itself. A cheap signer with good habits beats an expensive one without them.
Compare your options. See SeedSigner for the strictly stateless build, Specter DIY for the other DIY route, and Choosing a Wallet for the full picture. Official docs and downloads: selfcustody.github.io/krux. Builds welcome at any meetup.
Limestone City Bitcoin is not affiliated with the Krux project. This guide is educational and is not financial advice.