Build a SeedSigner

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SeedSigner is an open-source Bitcoin signing device you build yourself from cheap parts. It has no Wi-Fi, no Bluetooth and no storage for your keys. It talks to your computer only through QR codes, and it forgets everything when you unplug it.

For about $50 to $70, it’s the cheapest way to get a dedicated, truly air-gapped signer. This guide covers the parts, assembly, your first seed and your first signed transaction.

How SeedSigner is different

Most hardware wallets store your seed inside the device. SeedSigner doesn’t. Each time you want to sign, you load your seed by scanning a SeedQR: your 24 words written as a QR code on a card. When you power off, the seed is gone from the device.

This design has trade-offs:

• Good: Nothing to steal from the device itself. An attacker who takes it gets a Raspberry Pi with no secrets.
• Good: No USB data connection and no radios. Everything moves by camera and screen.
• Trade-off: You handle your seed (as a SeedQR) every time you sign. Store that card as carefully as your words.
• Trade-off: It’s Bitcoin only.

Parts list

Part	Notes	Approx. cost
Raspberry Pi Zero v1.3 with headers	Must be the version without Wi-Fi. Not the Zero W or Zero 2 W.	~$15
Waveshare 1.3” 240×240 LCD HAT	The screen and joystick SeedSigner is built for.	~$15
OV5647 camera for Pi Zero	Needs the narrower Pi Zero ribbon cable. Check it fits.	~$10–15
microSD card, 8 GB+	Holds the SeedSigner software only.	~$8
Micro-USB cable and a power bank	A power bank keeps it off any computer.	~$0–10
Case (optional)	3D-printed cases are common.	~$0–15
Dice	For creating your own randomness.	~$2
SeedQR cards or index cards	For writing your seed as a QR.	~$3

The Pi Zero v1.3 is often out of stock, and many listings ship without header pins. Buy one with headers already soldered, or add a hammer-on header kit if you don’t solder.

Several shops sell complete SeedSigner kits for around $60 to $90. That’s a reasonable shortcut. Check the official SeedSigner site for its current list of compatible parts, since supported hardware can change between releases.

Step 1: Flash the software

Do this on your normal computer.

1. Go to the official SeedSigner project (linked at seedsigner.com) and download the latest release image for the Pi Zero.
2. Verify the download. The project publishes signatures and instructions for checking them. Don’t skip this.
3. Write the image to the microSD card with a tool like Raspberry Pi Imager or balenaEtcher.

Step 2: Assemble

1. Connect the camera ribbon cable to the Pi Zero’s camera connector. The contacts face the board; check a photo in the SeedSigner docs if unsure.
2. Press the Waveshare screen onto the Pi’s header pins.
3. Insert the microSD card.
4. Fit everything into a case if you have one.
5. Power it from a power bank using the Pi’s power port (the one marked PWR).

It should boot to the SeedSigner home screen in under a minute. If the screen stays blank, check that the screen is fully seated on the pins.

Step 3: Create a seed with dice

SeedSigner can generate a seed from camera noise or from dice rolls. Dice are the easiest to trust, because you can see the randomness yourself.

1. From the home screen, go to the tools menu and choose to create a new seed with dice. Menu names vary by firmware version; check the current SeedSigner docs.
2. Pick 24 words. Roll a die for each entry the device asks for (99 rolls for 24 words).
3. Write the 24 words down in order.
4. Confirm the words when SeedSigner asks.

No phone nearby. No photos. Your 24 words should exist only on paper or steel.

Step 4: Make your SeedQR

A SeedQR is your seed encoded as a QR code. You’ll scan it each time you sign.

1. SeedSigner can display your SeedQR on screen after you create or load a seed.
2. Copy it by hand onto a SeedQR template card, filling in each square. It takes 15 to 30 minutes. Blank templates are available from the SeedSigner project.
3. Scan your hand-drawn card with SeedSigner to confirm it loads the same seed.

Treat this card exactly like your 24 words. Anyone who scans it controls your bitcoin.

Step 5: Connect to Sparrow (watch-only)

1. On SeedSigner, load your seed and export the wallet’s public key (the xpub) as a QR code. Choose Sparrow as the coordinator if asked.
2. In Sparrow on your computer, create a new wallet and import the keystore by scanning the QR with your webcam.
3. Sparrow now shows your addresses and balance. It holds no private keys.

Step 6: Receive and verify an address

1. Get a receive address in Sparrow.
2. On SeedSigner, use the address verification tool to scan that address QR. It confirms the address belongs to your seed.
3. Send a small test amount.

Verifying the address on the device protects you from malware on your computer swapping in an attacker’s address.

Step 7: Sign a transaction

1. In Sparrow, create a transaction and choose to show it as a QR code. Large transactions display as an animated QR.
2. On SeedSigner, scan your SeedQR to load your seed, then scan the transaction QR.
3. Check the destination, amount and fee on SeedSigner’s screen.
4. Approve. SeedSigner shows the signed transaction as a QR.
5. Scan it back into Sparrow with your webcam, then broadcast.

Step 8: Test recovery

1. Unplug SeedSigner. It forgets your seed.
2. Power it on and load your seed by typing the 24 words by hand (not the SeedQR).
3. Confirm the wallet fingerprint and first address match what Sparrow shows.

This proves both of your backups work: the words and the SeedQR.

Storage tips

• Keep the device, the SeedQR and the word backup in separate places. The device alone holds nothing, so it’s the least sensitive piece.
• Consider stamping your words into steel. See seed backups.
• If you later build a 2-of-3 multisig, your SeedSigner can be one of the three keys.

Is SeedSigner right for you?

Choose it if you hold Bitcoin only, like building things, and want a fully air-gapped signer cheaply. If you hold other coins, or want your seed stored inside the device, compare hardware wallets or set up an air-gapped laptop. The cold storage kits page has a checklist for each option.