Bitcoin Forum

I'm wondering what are the options are for making a homemade DIY wallet? I say homemade because the commercial devices with DIY options (such as Blockstream Jade, SeedSigner, Specter, etc) do not have some of the main features I seek in such a wallet. For one, such wallets are not optimal for travel, since they are easily recognizable as purpose-built devices made for storing and spending bitcoin. They even tend to be prominently labeled with brand names and logos suggestive of their purpose, so that even someone unaware of hardware wallets might guess their purpose. I would prefer to avoid the possibility of airport security or similar types recognizing the device, as bitcoin and related technologies become increasingly well known around the world, in particular to security personel. Secondly, they are difficult to purchase anonymously and I'd rather not leave such a direct record of my having obtained such a device.

A laptop-sized airgapped device is also unsuitable, as another feature I seek is maximal portability, something that could fit into a commuter-size backpack along with my main laptop and other items when there's no room for extra luggage. So, I'm looking for something that combines the best of both worlds, the portability of a purpose-built device and the non-conspicuousness of an airgapped all-purpose device such as a laptop. For example, a Raspberry Pi might fit the bill, as long is it can run Electrum. Would that be possible, or are there other ways of making such a device?

Even commercially available DIY kits for these devices don't necessarily have any distinctive features. You can completely customize the case to fit your preferences. In fact, some existing options could likely fit into a case resembling a regular USB flash drive or another common electronic device. To the untrained eye, such a device would be entirely unsuspicious.

A few threads you might find interesting:

Jade DIY hardware wallet (https://bitcointalk.org/index.php?topic=5454770.0)
$8 LNbits DIY Wallet (https://bitcointalk.org/index.php?topic=5413707.0)
Krux DIY Hardware Wallet (Unofficial) (https://bitcointalk.org/index.php?topic=5350905.0)
Specter DIY hardware wallet (https://bitcointalk.org/index.php?topic=5348779.0)
DIY Bowser Hardware Wallet (https://bitcointalk.org/index.php?topic=5291333.0)

As for Raspberry Pi solutions, check these out:

SeedSigner DIY Signing Device (https://bitcointalk.org/index.php?topic=5367858.0)
PiTrezor DIY Hardware Wallet (with a twist) (https://bitcointalk.org/index.php?topic=5355225.0)

Krux (https://selfcustody.github.io/krux/getting-started/) is the one I'd recommend.

SeedSigner (https://seedsigner.com) is great too, but Krux is a huge step up.

Krux features:

Free and open source.
Airgapped - hackers can't reach it.
Stateless - nothing on it for a thief to steal.
SeedQR - with optional encryption.
Passphrase QR - no more typing!
Etc etc etc.

Krux runs on Kendryte K210 devices like the M5StickV Stick, the Maix Cube, and my favorite, the Maix Amigo.  The M5StickV looks like a Blockstream Jade.  The Maix Cube is a tiny cube with a screen.  The Maix Amigo is a device that looks like a chunky iPhone & has a large touchscreen.

Krux on a Maix Amigo is a killer combo.  The large touchscreen makes the device easy to use, and having a large screen means everything is easy to see and shown clearly.  This matters a lot when confirming things.  Have you ever used one of those tiny Ledger screens where you have to scroll through an address to make sure its right?  Tiny screens are a safety issue, in my opinion.  The Amigo's large screen has room to show you everything, which makes using it so much safer.

My favorite feature is probably the encrypted SeedQR.  This gives you the ability to store a seed QR on your desktop or phone without worrying that somebody will find it.  Choose a strong decryption key (use a long passphrase) and your SeedQR is unhackable.  Oh, and you can create a QR for your decryption key too.

If you do TinySeed metal backup, Krux can scan it (https://youtu.be/BGY6sHuZdeA?si=5uotpWEZMAN6umle&t=245).  I'm not sure if this feature is part of the current firmware yet, but it's on the latest beta.

Since Kendryte devices are meant for development & hobbyists, buying one doesn't put you on a crypto mailing list that can get leaked like Ledger's was.  The clowns at Ledger (https://cointelegraph.com/news/ledger-data-leak-a-simple-mistake-exposed-270k-crypto-wallet-buyers) leaked users names, phone numbers and home addresses.  YIKES.

When it's in stock, the Maix Amigo sells for as little as $50.

Krux is such a fantastic project.

Thanks for the reply and the list of resources, I look forward to reading the threads on these wallets. I didn't realize the cases are customizable for the commercial DIY kits, which makes that option more suitable. That only leaves the issue of anonymous purchase, but there are ways of doing that.

Thanks for the recommendation, Krux may be just what I'm looking for.

Pair it up with a companion app, such as BlueWallet for mobile and/or Sparrow for desktop.  Both are free and open source.  Electrum is great too, but I find it clunky for making airgapped transactions, whereas that's easy to do on BlueWallet or Sparrow.

I assume you know this, but if not, what you'll do is get the zpub from your hardware wallet and import it into the companion app of your choice.  Then you'll use the app as your wallet app (it'll be watch-only), and you'll use Krux to sign transactions.

To get the zpub on Krux, select "Extended Public Key" & you can see the text and the QR code.  Scan the QR code to import it into BlueWallet, Sparrow, Electrum, or whatever wallet app you prefer.  Easy!

I really like BlueWallet for mobile, with its simple interface, and Sparrow for desktop.

You can also create a DIY Trezor Crypto Hardware Wallet and modify the outer case to be different from the shape of Hardware wallets, but in the end, I think that an airport security employee may ask you what this device is, so always add a secure element when make your own HW.

https://www.youtube.com/watch?v=mZmv4wG6_PE (Trezor code updates faster than most DIY solutions)

Advantages of DIY HW:
Possibility of adding a safe element.
Support for alternative currencies.

Other than that, I think burning an open source OS on USB and running airgapped on it would be easier, especially since you can get a PC at a cheap price and learn to remove network parts from it.

Thanks, good to know there's a way to make a DIY Trezor. Looks like a lot of work and troubleshooting though! I wonder if anyone other than that guy has actually made on of them  :D

A bit off-topic , but I use for travel Tangem 2, not DIY, but  cost affordable and almost purposely -disguised hardware wallet. You may even attach to its surface some film holding recognizable bank name to camouflage the stuff further or misrepresent it as a luggage tag,all depends on  on your creativity.

How about Satochip DIY HW smartcard based?

- Firmware is open-source: https://github.com/Toporin/SatochipApplet/releases/
- The beta v0.14 supports Schnorr.
- Supported natively by Sparrow Wallet.
- Compatible smartcard is affordable (eg: J3R180).
- Dual interface: chip (using USB smart card reader to connect it to the computer) and NFC (mobile ready).
- Long lasting.
- Waterproof.
- Discreet af.

More info: https://satochip.io/build-your-own-satochip-hardware-wallet/
And you can grab a compatible javacard over here: https://satochip.io/product/card-for-diy-project/

https://i.ibb.co/qr09HZF/Quick-start-DIY.jpg (https://ibb.co/YLD85rT)

If Raspberry Pi might fit your needs, have you consider Mini PC (e.g. Intel NUC) or Handheld PC (e.g. Steam Deck)?

I don't agree that they are a safety issue. It's not difficult to group the characters in your head and remember the last character of the previous screen before you switch to the next one. I find it easier to verify a bitcoin address on my Ledger Nano S than on my Trezor One. Ledger divides it in three parts, and the characters are bigger on screen. The Trezor One shows everything at once, but the size is quite small and I have to strain my old eyes. The new Trezor update will divide the addresses into groups of 4 characters I think. That's going to be the best option in my opinion because it's easier to verify group by group.

@zabzob
I don't think airport security will be able to recognize that your Maix Amigo is a hardware signer. But I understand your concerns. The Seedsigner and the Jade can work in stateless mode. So, even if security were to ask you to unlock the hardware wallet, or turn it on, there wouldn't be anything on it. You can always say it's blank, you are bringing it to a friend, etc. They surely don't have the knowledge or time to look for your xPubs and addresses to see how much bitcoin is on them.

Not off-topic at all (in spite of thread title  :D), as I am still considering non-DIY options, as long as they aren't too conspicuous. Tangem looks like it might fit the bill. With it's credit card size you could keep it in your wallet as you go through airport security. I see they also have a finger-ring option coming soon which looks cool. I'd probably go with the card though.

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Another credit-card size option, and very discreet indeed. Will definitely consider this one, thanks!

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I hadn't considered that option, but it might make sense to buy a cheap used Steam Deck and replace the OS. Would definitely not raise eyebrows at airports, since it's such a popular gaming device. It might even be possible to airgap it by removing the wifi and bluetooth modules, considering how easy it is to replace the SSD:

https://www.tomshardware.com/video-games/handheld-gaming/how-to-upgrade-steam-deck-ssd

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While looking further into this option, I came across this info from an Amazon listing for a J3R180 card:


So for someone looking to go cloak and dagger on their HW wallet, they could make a Satochip DIY, then print it to make it look like an ordinary ID card of the type used at workplaces, schools, gyms etc.

First a tip and reminder: Making multiple posts in a row like you just did is against the forum rules. Instead, you should make a single post and add multiple quotes to the people you are replying to.

You could definitely mask the Tangem as a debit/credit card and put it in your wallet with the rest of them. I don't see airport security asking you to take out your cards and showing them to the staff one by one, explaining what they are and for which bank.

But if open-source is one of your requirements, the Tangem won't tick that box. It's a closed source hardware device.

Oh my bad, thanks for letting me know, will avoid doing that in the future. I do prefer open source, so might go with a different option.

OP I would recommend checking out Satochip cards since this cards can be found even locally with reasonably low price, they have secure element and code is open source.
Only downside is not having a screen on cheaper cards and empty cards with screen are more expensive, but Satochip have mobile app for this purpose.
I won't repeat what other people wrote above me but you can also use your old smartphone offline for this purpose.

As reminder, the cheapest type (64 GB storage) should be enough for Linux and Electrum. And be careful you might get stolen Steam Deck if you decide to buy used ones[1].

[1] https://www.pcgamesn.com/steam-deck/second-hand-market-concerns (https://www.pcgamesn.com/steam-deck/second-hand-market-concerns)

So if I'm understanding this correctly, you can actually flash an entire hardware wallet onto a object the size of a credit card? Nice!

This is definitely something I'm going to check out as I haven't really followed Satoship at all really. The only disadvantage I think is that it's not supported natively by Electrum (yet), but I must say, I am quite impressed at how simple this process really is.