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I don't sell these, it's a personal project someone here may want to repeat.  :)

A short guide and more pictures on my main site:
https://pinode.weebly.com/hardened-cold-storage.html

So a while back I tried to punch/stamp these Stainless Steel business card blanks with address/Private key for safe keeping. But the Steel didn't mark very well and it was very time consuming. Aluminium did stamp well but has a low melting point and has a chance of not surviving a house fire.

Prototype with test (inactive address and key, although they are a working matching pair).

https://i.imgur.com/At6Hg7U.png

It was masked with nail polish, design laser etched, and then the metal was electro-etched with salt water. Copper Sulphate added to copper plate the etch.


Surprisingly cheap and easy to do at home. (Cheaper than hardware wallets). Also very cheap if you already own a laser toner based printer. A cool project to show your kids, with electro-etching and plating.

Pretty neat job there.  It's certainly safer than a paper wallet!  Have you actually done any testing for durability in fire?  I'd like to hear the results if you have/do.

This is better than a paper wallet, but I don't think this material will survive from rust and it will ruined, rust will destroy the "relief" including all your wallet code.

It looks pretty cool. I have actually been thinking about making something like this for myself :)

However I didn't understand what your material was. I know it is Stainless Steel, but you didn't say what exactly. Like what type, also what was the diameters, specifically the thickness.

I currently am in possession of a couple of plates with 1.5 mm thickness of AISI 420 (1500°C=2732F) , AISI 304 (1450°C=2650F), and another one that i have forgotten what it is but it is one of those Ferritic SS  ;D
which one do you think is best to use here?

I also would like to add that your end result has a couple of flaws. For instance your 3rd character in your address is wrong. you put "I" instead of "i" and your private key is not properly etched, in second line at the end there are 2 unreadable characters (it is easy to guess or even brute force it though).
What do you think was the reason, and what should we do to avoid it?

Impressed dude, it is a really good option than regular paper wallet. Have you finished all the test ? I would like to know more details about the results of the test. All the best best for your project.

For a moment there I thought the BTC symbol was floating in thin air, and then I saw the wood grain of the table going in the opposite direction. This is good quality workmanship and for proper cold storage and possibly for long-term storage, this might be a better idea than laminated paper wallets. < This might last longer in a fire too >

I store my paper wallets in 3 different locations, so I will have to make 3 copies of each. ^hmmmm^

Cool, I wish I can make one.

So for those that were asking dimensions I had the choice of:

Solid Aluminium Rounded Corners x 1mm Thick - 84mm x 54mm

Solid Copper Rounded Corners x 0.9mm Thick - 84mm x 54mm

Solid Brushed Copper Rounded Corners x 0.9mm Thick - 84mm x 54mm

Solid Brass Rounded Corners x 0.9mm Thick - 84mm x 54mm

Solid Stainless Steel Rounded Corners x 0.9mm Thick - 84mm x 54mm

And also those that said it's not quite completely formed I don't think any of the photos quite show the clarity. The "grain" effect on the copper in the logo is the dots of the pixels from the laser etcher, and you can see the pixels in the text too. It's pretty clear, not perfect, a few imperfections but as for the text the only character that needs a double take to read is a lower case "i" after the CG in the private key . I think the flaws could be solved by using a different font, (I used Veranda for it's legibility) perhaps another defines "i" better.

The table salt in the solution does the etching, the Copper Sulphate does the plating. Because I didn't have complete coverage with the copper, and stopped because I didn't want to over etch, next time I'll use more copper and less salt. Perhaps 6 teaspoons of Copper Sulphate and 4 teaspoons of salt (pint of warm water).

As for fire, we have an open fire at home and I don't mind putting this test piece into it, I may be month or so until it gets cold enough in the house to light it, you may have to wait for those results, the best I can do is phone the supplier of the metal and ask what the metal spec was for our best guess at a melting point, although it will of course soften before that.

I think that's answered most questions, keep 'em coming.

If you don't have or plan on getting a laser etcher, you can heat transfer laser toner to do this project cheaply too. It honestly was easy.

This is a cool idea. The only downside is that once you use a bitcoin address you are advised to never use it again, because the private keys have now been exposed to a third party.

Hopefully you don't have anything stored on that address, because the private key is now available to everyone on this public forum. :-[

I like that a lot. I'll see if I can get a good enough QR code on the back. As it got ok definition in the letters I think it could do it.


And it's ok TheGodson it's a test account, (with matching address/key pair, not sure why I bothered for this test) but I won't be using this one for funds. That would be level7 stupid.

He has actually done a great job. When I first looked at it, I was so puzzled that why the guy has put his private key and address on it. Then I came to know, these were inactive ones. But still, it looks cool and when compared with paper wallet, it is more attractive and reliable.

Yes, again just a test piece. To save you time from typing in the address to check here's what's on the card:

Address: 1PiNodemHPYocq6dRw9JhN5f8N1nC2VfXQ
Privkey: 5KYbHUHB4Bwa87pEvBgb4Aqj6KsRjCGiuvgNCHruz698MNwQpDJ

You're welcome to anything on it 'cause I didn't put it there.  :)

As for storage though it would be sensible to obscure the private key. Stop someone finding it and taking a picture/writing down the key. I was thinking a tamper proof label would achieve this? Any thoughts?

(It's a label that disintegrates when peeled, revealing "void" in the hologram)

https://i.imgur.com/KfJPqR6.jpg

That's pretty cool, great effort, thanks for the guide.

quick search says fireplaces can be 500F-1100F depending on fuel etc. house fires can be 1100F. a propane torch can hit 2000F. so if you can test it with propane torch (which are very cheap) and heat it to red hot say and have it survive that would be a good test. 

I can use a propane torch and get it to 2000F but I'm not sure that's a fair test:


Using the propane torch to me seems more like a test of the metal quality/spec than proof of survivability. I could easily have spent 8x more on really high quality steel/titanium/tungsten to be certain it would survive but that takes it out of the realms of an affordable home project for most people.

 I got the metal business cards from ebay, and as it's a prototype it was on the cheap. I think all steel has a melting point above what my open fire produces (and a house fire), my concern is that the card softens and distorts before that melting point, if it does I would consider it a failure.

Also, how about storing it in a zip lock bag with some desiccant (the sachet from my next pair of new shoes). Or rice. By preventing the moisture in the air getting to it degrading of the metal would be a lot slower. It is stainless steel so it will be very very slow, and on my first test I left the back exposed when etching and it just "pitted" rather than an all over rust.

not meant to be a fair test, just a cheap and dirty test. 2000F is still below the melting point of the metals mentioned in the thread (IIRC), figure if it can survive that, it can survive a house fire, no ifs, ands or buts.:)

too bad there are no cheap IR temp guns that can hit 1100F (typical house fire temp), my cheap one maxes out at 830F. otherwise you could use the IR gun with the torch to hit 1100F and hold it there to see if it deforms/melts.

only some fireplaces/fuels burn at 1100F so not sure how you could easily and reliably check that.

Bookmarked, this is really cool, I have been thinking of a better way to store your bitcoin than a paper wallet and this is great, I have a question how much did it cost to you to make this card? And how much it could have cost with premium materials? I think you have the potential for a small business here.

Edit: it seems that I skipped the part in your link where you said that the cost was 5 dollars per card, sorry I missed it. :P

Good job, your wallet looks great and it's much more cooler than a typical paper wallet.
Now, I don't think that "Cold Storage" is a correct word here. By its function your wallet is the same as paper wallet, just made with a different material. Cold storage refers to an electronic device - it can be some specifically designed device like Trezor or Ledger Nano, or it can be some spare smartphone/laptop/computer. This device must have key management software on it, so you can generate addresses to receive transactions and also sign transactions. It's called cold because it's never connected to the Internet to avoid any security risks, and you spend coins by creating signed transactions offline and then broadcast them from a different device.

Nice work. That's very good that you were able to make such a nice looking wallet back up. I really love that it's wood. Dire proof and water proof is a great thing. Perhaps it is a must. I have seen less then 1ml of water ruin a whole printout beyond recognition. This is really bad and your wallet backup design prevents that really well and it looks great and artistic. Very good job and thanks for sharing it with us.

Looking good but I don't think anyone else will order this from a third party source. Instead they will try to create their own.

Yeah, there is no way you should share your private key to anyone to make something like this. It really was simple and cheap to make.. Another user did this in a similar way in 2013 with print toner http://www.instructables.com/id/A-Stainless-Steel-Bitcoin-Wallet/.

Out of curiosity has anyone else had success with a different method? I think my method is very cheap but it's only the masking of the etching area that if delicate/most costly.

I've heard there are some commercial powders that can be bonded to metals with a laser. And a home method that  achieves the same with plaster of paris and isopropol alcohol. I'll give it a try the next rainy day in I get.

Good work dude. It looks easy to made. I'll make my own soon.

Has anyone else had a go at making one yet? Or thinking of giving it a go?

Great job done, it is probably the safest wallet to keep at home. I have some questions if you don’t mind.

1) How long did you take to complete this project?

2) Did you test the durability of the wallet using fire and water?

Was thinking about similar, already mentioned on the forum, but it's a bit different.
I was using the same kind of metal business card, but I would like to engrave the letters into it with a hand engraver tool. My initial thought was to punch in the letters like a dog tag, but there's not enough place to punch all the letters, because of the blending of the material, you can't condense the characters enough to fit. So I have already ordered the metal cards off from ebay, now I'm searching for a proper hand engraver.

There's really no need to. He said it's stainless steel, so it's basically what the inside of a water boiler or your dishwasher is made of. It can withstand being submerged in boiling water for months and not have a speck of rust ;) It's also quite resistant to weak acids, salt and other chems.
You only have to make sure the etches are deep enough so that normal scratches and metal wear won't make it unreadable.

1) My short guide is here https://pinode.weebly.com/hardened-cold-storage.html but in steps it took...
* Create the vanity address and key with a Raspberry Pi, 2 days (unnecessary from a security point of view) but if you're interested https://pinode.weebly.com/bitcoin-vanity-address.html
* Paint metal card with nail polish and mark design into the polish 40mins
* Prep the etching solution and electrodes 15mins
* Etching 2 mins
* Cleanup of the finished card 30mins

* Total 2 hours with added messing about, second guessing, checking etc

(The design was marked with a cheap laser etcher but can also be done with a laser toner printer, heat transferred on with a household iron.)

2) Now it's getting colder here in the UK I'll be testing it in the fire soon. In theory it should be fine but I'll post the results here with pictures when I have them.



My first thought was using letter stamps too. I ran into problems.
1) The stamps needed to be upper and lower case due to case sensitive keys and addresses.
2) Aluminium stamped well, but has a low melting point.
3) Metals that had a higher melting point are considerably harder than aluminium and did not stamp well at all, barely left an impression.
4) As I continued practicing with the aluminium it was very hard to stamp the many characters in neat straight lines. End result was very amateur.

If you're looking for a hand engraver and it gets to around £50 then I would instead recommend looking at getting the laser etcher I did. The laser etches wood, paper and most plastics. Then to etch metal and glass it can still do the marking out very neatly into nail polish, then apply glass etching gel or immerse into a chemical bath for metal as I did.

Do you mean something similar?
https://www.ebay.com/itm/1000mW-Adjustable-Focal-Laser-Tube-Wood-Kits-for-NEJE-DK-8-KZ-Engraver/263236760459?hash=item3d4a22338b:g:xQUAAOSwFYxZzopa (https://www.ebay.com/itm/1000mW-Adjustable-Focal-Laser-Tube-Wood-Kits-for-NEJE-DK-8-KZ-Engraver/263236760459?hash=item3d4a22338b:g:xQUAAOSwFYxZzopa)
I was searching thru ebay for laser etching, but only $500+ machines were listed, so now I'm searching for laser engraving tool, and this was something similar that you probably mentioned.

This is indeed a nice project, but like with most nice DiY projects, you relied on having a lot of existing stuff on-hand to begin with in order to make your final product so cheap. For those of us without laser etchers, chemicals and the like it would be quite a bit more. This isn't to detract from your project in anyway, just an observation.

I think the best idea for those who only need to store only one or two private keys would be to get one (or more) of the Cryptosteel (https://cryptosteel.com/) products. The nice thing about these is you can assemble any address and reuse it once you send the funds off your old private key. They do cost more than the DiY method, but again it is a scale thing. If you are going to make 10 or more homemade keys then yes that is probably the cheaper method once you acquire all the ancillary equipment and chemicals to make it possible, but if you are only looking at one or two keys than i think the commercial  products are probably the way to go.

Yeah, to replicate it exactly then the laser etcher was something like this one...

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F282624625105

And as for chemicals it is just table salt and water for the etching solution. The added copper sulphate is optional and only about £3 on ebay or amazon.

As I've said before though this can be done with a paper laser toner printer to the same effect, and heat transfer the image to the metal before etching. Someone did this years ago and made a guide here:
http://www.instructables.com/id/A-Stainless-Steel-Bitcoin-Wallet/

There are easy ways to avoid the setup costs, the easiest by having access to the office printer at your work would do it.

Wow, this is a great hard wallet to have. I am really looking for someone to make me this kind of hard wallet in my country. You are so lucky to have some skills and tools on your own garage to make this kind of card. And for some little suggestion, maybe you can make some other version of it, with other colors pattern, like white and gold, or etc. And i see that you are giving the guide to make it too to people.
This is some great DIY. Damn, you must proud of what you have made bro, well done !!

Thanks for that, I've checked the instruction of etching. It's really straight forward, I'm planning to try it out sometime.
What I would change is:
For me, it looks easier to just put my seed on the steel card, because I can easily import it into any kind of wallet in a few minutes. In this case, if someone finds the card with some words on it, it won't be easy to determine if it's a seed, and for which kind of cryto and what kind of wallet it is useable for.
Also, if I etch the seed into two cards (half of the seed to the first card, second part of the seed to the second card), I can place them to different offsite locations. In this case I don't need to worry if someone finds the card, because the other part is far away. Just to be a bit too cautious :)

Yes this is a good method. Using stainless steel is fine for resistance to corrosion and fire. Check the etching process digs into the metal, can use a torch to do that. Get the metal red hot, see if the characters survive. Might I suggest encrypting the keys, that way you don't care if anyone sees them? I think the protocol was BIP38. RE the scan QR code, what it really does is provide a backup - a 2nd copy of the dataset.  Good idea, two copies. For that matter, why not a couple more. Better a couple copies of the card than the same time spent doing the front and back on one card.

As requested, fire test results night.  :o

A little overdue, but tonight was cold enough at home to light up the fire and put in the test piece.

https://i.imgur.com/kVqCH3k.jpg

The fire, coal at its base, a mix of softwoods above.

The test piece is in centrally and the fire was kept fuelled at a level similar to what's pictured above for roughly 3 hours. When adding new logs the metal could be seen to be glowing orange/red.

https://i.imgur.com/pZNlSx1.jpg

End of the evening, metal cooled slowly.

https://i.imgur.com/F0iROHz.jpg

Lightly brushed (dry) to remove soot. Some letters obscured.

https://i.imgur.com/3VjHnIb.jpg

Next cleaned with a mild abrasive (plastic dish sponge and water).

https://i.imgur.com/6p0ujVd.jpg

First observation - The heat of the fire appears to have melted the copper. The copper was the decorative plating added to the bitcoin logo and lightly to the lettering. The now seems to be the orange splodge in the middle of the card. A google of coppers melting point puts that at 1,085'C. A search for typical fireplace temps ball park figures depending on fuels for anything between 800'c to the max theoretical adiabatic flame being 1977'C.
According to http://www.doctorfire.com/flametmp.html a typical house fire reaches as sustains around 1097'C. More to read there if you're interested.

Lettering now is readable with just 4 of the characters in the private key obscured beyond certain readability. An 'E' could be an 'F' in the end of the top row and the 'v' at that point was now readable.



So I moved on....

https://i.imgur.com/gBYglzO.jpg

These last two pictures are after a clean/light scrub with "Brasso" metal polish. I'm sure any light abrasive cleaning fluid would do.
This made a huge difference and removed a lot of debris from the fire. All letters a lot clearer now.

https://i.imgur.com/nf0XXeh.jpg

It's tricky to photograph but I assure you the private key was then legible with then just 2 characters requiring some time/interrogation to confirm.



Where to go from here -

If the purpose of making these was purely for function then I don't recommend the decorative copper plating on the logo/text. Coppers melting point is too low for this task. It may also cause issues in several year with corrosion on it's own or though the effect of dissimilar metal corrosion. The stainless steel card handled the heat very well. There is a slight deformity in the centre of the card. Perhaps 5mm in length, a slight shallow dent. I suspect the metal may have softened slightly in the heat and the addition of a weighty log may have caused it.

I would, in my next test, etch slightly deeper to aid in the reading of the text.

But to conclude I regard the prototype a success and it performed it's purpose. For a homemade DIY project that has sat at around 1000'C for the past 3 hours it's handled it well. That test piece was only the second I've ever made and I'm certain my next will be significantly better with those improvements.


I hope this helps and I'm happy to answer any questions about this, or to help someone with anything regarding giving this a go for themselves.

Has anyone else had a go at making one of these yet using laser printer toner and then etching?