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What happened in Turkey made me think carefully about how to keep my cold storage wallet seeds.

I keep them in a waterproof and fireproof notebook, but is there any proof of the efficiency of this Metal Seeds and/or notebooks with earthquakes? Does it bear the violent shocks?
What are the solutions, in your opinion, if an earthquake occurs? Or in other words, the best solution if you are in an area active in earthquakes and tsunamis.

- Yamane

Redundancy and off site storage.

A stainless steel metal plate of sufficient thickness will likely survive an earthquake or a building collapsing on it without significant damage. Jameson Lopp has tested many such devices under a 20 ton hydraulic press, and devices which are simply steel plates hold up very well under such conditions (any device with moving parts such as tiles, not so much). You can see the results of such stress tests here: https://jlopp.github.io/metal-bitcoin-storage-reviews/. However, having your metal plate survive is not much use to you if it is buried under several tons of rubble and you will never find it again. Similarly if you are in a tsunami region, your metal plate will survive just fine, but is no use to you if it is buried under rubble a kilometer away from where you stored it and you will never see it again.

So you need redundancy. This means more than one back up, so if one back up is lost you have others you can rely on. And these other back ups need to be geographical separate, so if a natural disaster affects your city/town/village you have a back up in a different city/town/village which is unaffected.

It depends what type of metal you are using, but good stainless steel washers or thick plate blocks will withstand earthquakes, water and high temperatures.
Notebooks and laptops can survive only if you are using quality military protection brands like Thinkpad for example, but I can't be 100% sure what will happen f building crumbles.
Good Thinkpads are known to survive fire, water and fall on ground, but I wouldn't keep digital seed phrase in any laptop.

Best protection is to use passphrase and distribute seed phrase backups in multiple locations, cities or even countries, and multisig setup is  best for larger amount of coins.

This is not a good advice but may sometimes be the only option left. Turn your seed phrase to a national anthem and enjoy it every morning while reading it offhand. Do not trust your memory, but you can use it as the fourth backup that you should not rely on. People do have more than one seed phrase wallet, this can make this impossible. Again, not a recommended option.

While having the seed phrase in far different locations, passphrase would be recommended. But can it be in reality that people can have their seed phrase elsewhere far from them, like in another town, state or country? Most people will not see it possible or convenient for themselves to keep their seed phrase far from themselves, but it would be a good option to go for if it is possible for him and safe.

I think it depends if everything falls on the steel. If something does fall on it then I do not think it would survive a part of a building would destroy it or scratch it beyond repair. There is not a lot you can do to protect against a earthquake unless you can put your seed in a area where earthquakes do not happen. There has been no reports in the turkey news but I expect a lot of people lost their seeds during the earthquake through damage or it getting lost.

If there is a seismic hazard in your area, then along with waterproof and fireproof, you should think about protecting seed phrases from earthquakes. In my opinion, the most dangerous elements here are building structures, such as various heavy objects, such as concrete walls and metal elements. When crushed and dropped by their own weight, these parts can damage the metal crypto storage and make the information unreadable.

How can this be prevented? I think it will be necessary to use thicker metal plates, or even better, several at once, like a sandwich. That is, the main plate with text on both sides is covered by 2 other plates that take all the damage to protect the main plate from deformations and damaged text. The multi-plate construction will have greater rigidity and will not bend like a thin piece of metal.

https://jlopp.github.io/metal-bitcoin-storage-reviews/reviews/cryo/ - something like this, but I would replace the threaded bolts with hard-fixing rivets (as a bonus, it will be immediately noticeable if someone opened your vault) so that the threads would not be torn off and the plates would not separate from the impact.

It is better to have an extra margin of safety than later to have difficulties with the readability of the seed-phrase during restoration.

Let's say you manage to make the storage strong and reliable, but another question arises. Will it be possible to find your seed-phrase under a bunch of rubble and will you be the one who found it?

If a 1000 tonne building falls on your seed no thick metal is going to prevent it from getting damaged it would be damaged beyond repair. It would be crushed and two extra plates even if they were 2" thick would not protect the plate in the middle. Then there is the problem of recovering the plates because you are not the one digging up a 1000 tonne building it will be the emergency services and they will not allow you to go near so they will take that seed or metal not think any more of it and throw it in the trash pits which you have 0% chance of recovering.

The only way would be to remove your seed from a earth quake prone zone.

The durability is one thing but recovering it in the rubbles is the hardest part especially if you live on multiple floors building because you will need to remove all the debris which normally leave behind when there’s no people need to be rescued.

Having a backup of your seed phrase somewhere else is the only way to counter this event. I personally leave my backup private key on my grandma house in the province and the pther one stays with me. My grandma didn’t know what it used for same with their neighborhood. I feel safe when I have backup somewhere else instead of doing all in.

On the first point, I disagree with you. A 1000 ton building doesn't purposefully fall with its entire mass onto your seed-phrase plate, so the force applied to the plate will be less. This is due to the fact that the building, when falling on its way, will encounter obstacles in the form of walls and floor slabs, which will extinguish and take on the load. I assume that even in such a building the plate with seed-phrases will not be badly damaged and keep the text readable. Again, the random factor plays a big role here.

On the second and third points here I completely agree with you. In the ruins and rubble, it will be unrealistic to find a small piece of the plate (if you are allowed to do this), which will most likely end up in a landfill and be lost to you. In the worst case, someone else will find the seed-phrase and no one will like this outcome.

Therefore, the best solution, as you said, is not to store the seed-phrase in earthquake-prone regions, because, as discussed above, there will be no sense, even using a reliable storage method.

It's not convenient, but if the alternative is losing everything, then it is preferable. It doesn't have to be the only copy of your seed phrase - obviously you can keep one close by which is convenient to access should you need to - but any back up which is safe from catastrophes in your local area will by necessity be inconvenient for you to access.

Good quality stainless steel of a reasonable thickness would survive just fine, especially something 2" thick as you suggest.

If a 1000 ton building collapses, then that full 1000 tons will be spread out over the entire area that the building collapses on to, which will be the footprint of the building plus more, since the rubble will fall in all directions. An average steel plate is maybe around 10 square inches, a tiny fraction of the total footprint. And as I said above, Lopp's stress testing shows that such devices can easily withstand 20 tons of pressure. To have 20 tons of pressure on 10 square inches, you would need all 1000 tons of the building to collapse on to an area less than 2 foot by 2 foot, which is obviously crazy.

Try to imagine it: This is the building you used to live in.

https://cdn.theatlantic.com/media/img/photo/2023/02/turkey-syria-earthquake-photos/a01_1246837213/main_1500.jpg

Do you recognize your apartment? Can you see the walls of your room? Do you see the shelf where you kept your seed tucked away somewhere? Do your recognize your airgapped computer somewhere?

The question here is not if the plate will survive the disaster, it's how you will find anything in the wreck. After almost two weeks of digging and looking for survivors, it's time for heavy machinery to step in and clear the area. There won't be any place or time for you to look for a piece of metal.

Imagine a huge box of Lego sets that's empty. One person will fill it with Legos from a bucket while another one drops half an eyelash inside at some point while the box gets filled. Do you think you will find the eyelash? Maybe. I think your chances of finding your metal seed backup are much worse.   

Are there any reports from Turkey of people losing their cryptocurrencies due to earthquakes? I know that it is early, but most of us do not take such an option into account, and the operations to search for a piece of stainless steel metal in such debris will be difficult, as the focus of the authorities will be on saving lives or recycling the debris quickly, and not saving your coins.

We might never know as the people who could have lost their crypto backups might also be dead or seriously injured. :-[
I think the confirmed dead count is over 45.000 already. I am afraid you will be able to add a "1" in front of that number when the whole thing settles. Whole villages have disappeared together with many parts of cities. How does one even confirm the dead count in that case? You can only make estimates. 

I think human lives are more important than any crypto and metal plates, there are estimates that more than 50,000 people lost their lives in this earthquakes.
Most people and rescuers probably wouldn't know how valuable piece of paper or metal plate is in situations like this.
I heard several stories from rescue teams that found a lot of fiat paper money hidden inside furniture of one apartment.
In one examples they found $2 million in a bag, and owner didn't survive, he couldn't bring all that money with him in a grave:
https://punchng.com/turkey-earthquake-rescue-team-discovers-2m-buried-in-rubble/

Another case of rescuers finding $150,000 in rubble of residential building in Turkey:
https://tass.com/world/1576015

What if the metal sets to store one's seed came with a small tracker device which could be activated remotely from one's phone or from a computer? If the steel wallet is sturdy enough, the built-in device/chip could survive the earthquake and then it would be just matter of using one's phone to localize it while the cleanup operations are going on.

There are a lot of issues with such a concept.

Either it is placed on the outside of the device, in which case it could easily get destroyed in such an event as an earthquake, or it is placed inside the device, in which case the range will be very short (if at all) given that the signal needs to penetrate the stainless steel in order to get out. I suppose you could engineer a device encased in stainless steel with just a very small antenna reaching the outside of the device, but you are now adding a lot of cost. You would need to access your back up semi regularly in order to recharge or replace the battery, which increases the risk of it being discovered. And then of course anything which can broadcast a signal can have that signal intercepted or detected by malicious attackers. The last thing I want on my back ups is any kind of wireless connectivity which could be used by an attacker to locate them.

Better to simply have at least two back ups stored geographically separately.

Fair points.
I am personally of a fan of the idea of having different backups in geographically distant places, I am paranoid on whether someone else could find one of the backups by chance. Granted, it can be done in a way which one would be the only one able to recover the information. I would consider to do it by splitting the seed in two and separate them in different places.

We aren't too different from pirates burying their gold, aren't we?

If you want to just store your seed phrase in two geographical location and you want to avoid inconveniences, you can use a strong passphrase while generating your seed instead which is the best for conveniences in my opinion. Or instead you can just go for a multisig wallet if you want to go for your choice of backup, instead of splitting the seed phrase.

I agree with Charles-Tim. Do a multi sig with one in your home, one is with you, one is someplace else and another is in yes another place.
Pick the amount you want to have and the amount you want to need to have to restore to move the coins.

Might not be as convenient but so be it.

-Dave

Does the average person really have that many places to store the credentials though? I feel like they don't, and by splitting it up in places which you don't own, you present yourself with even more risk. While, I like the idea of a multisig, storing the credentials in two different geographical places is pretty hard. Especially, securely.

Of course, we've all heard the stories of people digging in a random field, and storing various things. However, I've never been much of a fan of that. What happens when that gets dug up by a construction company to build the housing on it or whatever the circumstances is.

You ideally need to own, and no one else has access to it, even theoretically.

The little detail that keeps me from being fond of passphrases completely is the idea of lost coins, in the case something happens to me and my family cannot retrieve the funds. They barely understand the concept of a seed phrase.

I suppose it is matter of patience and time. Thank you all for your opinions, I don't intend to derail this thread any further.  :P

I too think something like that will be difficult to do, storing seed phrase in two geographical location, but we just assumed that the person wants to go for the option and know the disadvantages already.

They might lose the coins because they barely understand the concept of seed phrase? I think that is not hard to learn, also not hard to teach. Even it is a good idea to start teaching them about bitcoin and how to recover coins through seed phrase back up. All that is needed is just the time to teach them. You can teach them, send them bitcoin on a noncustodial wallet generated by themselves, tell them to delete it, install back the wallet app to spend the coin in a way they can convert it to fiat, just to let them know how valuable bitcoin is, instead of sending them fiat directly. No one will joke with what they know that it is money.

As long as they know how to access your back ups, it isn't a difficult concept to figure out.

If they came on this forum and said "Hey, I have a seed phrase which I have recovered but the wallet is empty/almost empty. I also have a password but I don't know what to do with it.", then they would very quickly be directed to use the password has an additional passphrase and recover the coins.

Can the average person think about all possibilities? I live in an area where there was no seismic or fires before, but we are near the sea, so I keep the seeds in its normal storage, it is in paper that is not a waterproof or fire. so if something like this happens, my wallet seeds will disappear.

The strange thing is that I feel safe and not even think about developing solutions for such days. I do not know, does everyone feel that?

Indeed, this is where storage gets way too complicated to make it a cheap thus affordable and reliable solution.

You either go for the cheap and easy way to deal with, like placing a tracker like an airbag in it, but which under 10 feet of concrete and rebar won't be detectable at all, Bluetooth doesn't penetrate that deep, or you go for a more complex and powerful solution which will need a third-party service, a huge battery that will increase the size, which might solve or add another problem on top of an existing one.

With a small box, it's highly possible it will not get noticed among the ruble just get thrown with the trash in a truck and dumped before you're even allowed to reach the scene of the disaster, with a huge box, there is the problem of it getting stolen as some might mistake it for safebox before you have the chance of getting it back. Plus if you make this big and durable, you have to hide it also pretty well in your house in normal times for the same reason, thieves getting in and thinking it's a safe box full of money, which actually it is  ;)


Yeah, easier said than done.
It was hard for me to find a place to store a pair of keys in case both me and my wife lost ours, (obviously, the inside of the house was a no), and with a hardware wallet, you must exclude a person keeping those, so, how many people have 2- or 3 properties with land so they can bury a case or a box far away from prying eyes?


If you're living above the third floor or even better you don't have tsunamis at all in your region there is not really a matter of concern. But you could at least laminate it to avoid normal degradation or accidents like your neighbor flooding your apartment.

Not many. I know I don't, unless I enlisted the support of family members. However, how many people are prepared to trust extended family members? Since, closeness, and therefore trust of family can vary depending on the individual. There's only a few people in the world I'd trust without any questions asked, but I'm not sure I could trust their security. As a person, they might be the ultimate trustworthy person, but because they aren't aware or as concerned about security, I wouldn't trust them to handle something so sensitive.

I'd like to see some alternatives rather than just saying to new users store it in multiple locations, because the reality is not many people can do that without additional risks.

Hey, now you mention it. I had not considered to actually instruct them to come here for advice if they needed instructions during the recovery. That a very good idea.    :)

Better than them crossing paths with someone asking them for the seed and the pass to "help" them.

Don't hide the seed backup in a crack house two blocks away, where you have to fear that someone may one day find it. Different geographical locations could be your parent's house if they live in a different city. Your grandparents or your siblings' place of living. It should be with people you trust most in your life where you don't need to worry about them stealing from you. If you have such trust issues, better keep the seed backups all to yourself and try to find an alternative method of storage. Even if it's in the same location. 

Don't forget to tell them never to share or make pictures of the passphrase or seed to anyone on the forum. You don't want it to become a case of your family saying we have this weird bitcoin thingy and then pictures of the seed and passphrase. How do we use it? It might sound silly, but I am sure it wouldn't be the first time someone makes a mistake like that.

Even if you live in an area with no earthquakes, tornadoes, floods, etc., your home is still not immune to a simple fire. The point is that if your only back up is stored in the same place you store your actual wallets (be they hardware wallets or software wallets on a computer), then your entire system has a single point of failure.

Yeah. Just tell them not to share any information about your back ups and to keep everything in a public thread and don't respond to any PMs. There are many examples of such threads on this forum and the community are always very willing to help someone recover their coins.

From Amazon I can find water and fireproof safe box starting from $35+ (https://www.amazon.com/s?k=water+and+fireproof+safe+box+for+home&crid=2OYU5UWUVG3FJ&sprefix=water+and+fireproof+%2Caps%2C485&ref=nb_sb_ss_ts-doa-p_1_20) so its worth buying and can be more cheaper with some deals and coupons or nearby shops, but more compact the safe then it will be easier to keep it secured and hidden since we are only going to keep piece of paper(s).

With the climate change I can feel unusual rainy season and pour all of sudden which is supposed to rain for over s period so taking precautions before losing our assets is the smart decisions.

Honestly, I wouldn't cheap out on a good safety deposit box if you really want it to be water and fireproof. I am sure it would be a horrible feeling getting one that turns out to be semi-water/fire proof. $30 for a good product seems like a toy for children. I am thinking more like $100 if you want something worth the trouble. And I would also Google any safe I intend to buy and look for professional reviews where they show if the product really protects the contents against water and fire.   

Here's the thing though - if a fireproof safe was a completely, 100% reliable method of storing things, then you could just put a paper wallet in it and be completely safe. There would be no need for safe deposit boxes at banks throughout the world. Cloud storage would be unnecessary, since an external hard drive in a fireproof safe would be 100% safe. And so on.

A fireproof safe is not a bad suggestion if you absolutely can't have offsite back up, but these things fail, they are not immune to physical damage, they are not immune to theft, etc. And as Pmalek points out, there is a degree of trust required in the manufacturer and the manufacturing process.

There simply isn't a way to completely reliably replace an offsite back up.

I said we can get from 30 so for someone who just looking for basic boxes can consider these inexpensive which also got have 4+ ratings the actual sturdy one which I noticed is 299 if I am not wrong and it looks good.

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But keeping paper in our hands is easier when we comparing with keeping gold and fiat money that is why bank deposits were famous for but nothing is completely safe so keeping at least two backup in different secured place can give us chances to recover the wallet in case one thing lost due to natural calamities and we are still alive out there and need money for survival.  ;D

I checked a few of those and there are 5 ratings from people that do mention they haven't been through the fire with it, so, are those ratings completely true if the box wasn't actually put to the test?

From my army training and the years I spent with inspections on the farm's buildings, there are a few things you need to look at in those so-called safe boxes, the temperature they are rated and the amount of time they are rated for at that temperature.
So if it's safe for 2000C without the time then it means it's garbage.
No safe box should ever have under an hour of constant +1000C, the average house fire goes to 800 and it can keep those for more than half an hour without intervention, so most of those "silicone fiber glass " and other stuff is useless, they throw at you a certification that really means nothing, like the 30$ box that shows a UL94 classification which is for the material itself, not for the protection of the content.
Two guys are asking for the fire rating and the shop owner just avoids the question going bla bla bla.

I don;'t know maybe it's just me but storing more than 1 BTC in a cheap $20 alibaba safe (yeah I know it's amazon but I've seen enough resellers to not care anymore about the brand)  seems like a really not so good idea!

It goes back to testing this sort of stuff out yourself, in order to be sure. There's so much misdirection with advertising, and specifications you really can't trust the manufacturers word on this sort of thing. It'll come at an expense obviously, but I'd rather be safe than sorry.

I doubt many users would be willing to one, and test it out or even have the means to do so, but it's a valid point that should be considered when storing anything of value in anything that apparently has a certain specification. Same as when it comes down to metal specifications, how many times I've had mixed metals when it's suppose to be pure is beyond a joke.

As an example that I just stumbled across via Reddit this morning - a lockbox called the MojoBox. Selling on Amazon for $70. Lots of boasting from the manufacturer (https://hello.showmojo.com/mojobox/) about operating between -30 and 140^oF, being water resistant, having a hardened enclosure, tested against physical force and pry attacks, yadda yadda. Then the Lock Picking Lawyer comes along and shows that it can be opened by slapping it. No, seriously. https://www.youtube.com/watch?v=k3bS1oLEbIM

Which goes back to my point above. If a simple fireproof safe was actually completely safe, then everyone would use one and there would be no need for anything else. But this is simply not the case.

I wouldn't waste money on some state of the art fireproof safe, but it's not a bad idea to buy fireproof bags that are not very expensive and they can have multiple use cases.
Similar bags can also protect from RFID electronic attacks, and there are waterpoof bags that can be very useful for everything.
This can be later hidden anywhere you want, it doesn't have to be safe deposit.

I don't see any difference between seed phrase stored on paper and fiat money that is printed on paper  ;)
You could say that seed phrases are better, safer and you print them yourself, but I don't trust banks on keeping money...it's all fake numbers on screen.

I agree.
Jameson Lopp did amazing job with testing all kind of metal seed backup options, and there are guys who are testing cars, smartphones, and everything else... so why not.

Resellers are out there who is buying from chinese website and resell them on Amazon and just wanted to mention that we can get the least protection instead of nothing with 30 dollars.

Personally I don't use any of those safe boxes because we have a vault which is almost weigh half a ton from my assumption where every documents are stored and its completely fireproof but never been tested as far as I know but on the paper iron can withstand upto 1500°c so it's good against fire and I don't think there will be any kind of flood or something where I am living.

I think that when we create a bitcoin address, we should consider absolutely everything:
1. Where do you live? How often do earthquakes, Tsunamis, storms and other natural disasters happen? How resistant is your building against natural disasters? If you have house, penthouse and your area is safe, you can risk for a while and save your seeds there but if you live in apartment, you should always be more cautious.

2. The best way to save yourself is to memorize seed phrase. There are a lot of people who hold bitcoin for years. Imagine, you have memorizing seed phrases absolutely every day, up to 30 minutes a day at first and then reading it up again and again. You have to imprint it in your brain. You have to imprint it so well that even if you get amnesia, you should be able to recover that information :D I mean, at some point seed phrases should become obsession for you.

3. Remember rule N1 and N2. Print seeds on Metal Storage, save it in two possibly safest area, don't waste time and start memorizing of seed phrases. When you think you have truly memorized them and there is no way you'll forget that, then either destroy your seeds or come up with a better plan.

Analyze these steps yourself, be sure in your cognitive capabilities. I think this is the safest option but options are very individual. You may live in a very safe area, your house is built well, there aren't happening severe natural disasters, people don't know about bitcoin, no one has doubt about you, so on and so on, this is a very individual case, I just say what I think is generally the safest option to my mind.

Memorization is the worst possible way to back up your seed phrase.

People with amnesia (from any cause, of which there are many) can forget their own name and fail to recognize their immediate family members. They can easily forget a seed phrase.

This is awful advice. If you are ever in a situation where your only back up is your memory, you should either immediately write down what you can remember and test it is still accurate, or you should move all your coins to a new wallet with a properly backed up seed phrase.

Why is it the worst possible way?
When I was a teen, I created bitcoin wallet and remembered seed phrases. Still, today, I remember those phrases. I mean, 8 years have passed and I still remember them. The problem is that I was using words from seed phrases with some additional combinations as a password and I'm never gonna return to that wallet but I still memorized the seed phrases of my recently created wallet and I always memorize my card numbers in case something happens. I also have different passwords for everything, never had a problem since my childhood. So, what's wrong with it? Why is that a bad practice?
Amnesia was a fun example. Definitely, if you get severe amnesia, nothing can help you, you may won't remember what bitcoin is and whether you have it or not but in light cases, there is a chance.

Because your brain is incredible fragile, and millions of people each year suffer significant brain injuries which can lead to memory loss, at no fault of their own and with absolutely zero warning. And even without such an injury, people forget things all the time. I certainly don't want the possibility that my back ups simple cease to exist at any moment in time.

The brain deals with numbers better. For example, you can remember your bank account if it has numbers less than 10 digits, and remember one-to-five different password, but you will not remember all your passwords or phone numbers on your phone.
Many psychology experiments have found that the maximum number of words can be remembered, which is 7 words on average, which means that you need to write 5 words, otherwise trying to brute force It will cost you a lot.

The day you stop using it regularly, your brain will become a little more fragmented. The thing is, our brain is somewhat good at short term memory, however the longer you leave it the worse it gets. That's without considering aging, various conditions the brain can be subject too, and the fact that no one can predict a fall which could damage the brain.

I know of someone who died while riding their bike, but it was probably just as easy for them to have sustained brain injuries (which is what happened), not died, and have memory loss as a result. In fact, it was determined that if they did survive, they'd have significant brain damage. That's just riding a bike, but we all drive cars or even walk has a little bit of risk associated with it.

There's a ton of things in life that can happen, that you just can't prepare for. You can try, and plan ahead, but you'll unlikely cover all the basis' unless you have others that can help you, i.e trusted people within your life.

Yes, Metal can survive a house toppling down (see stresstest links below), but you shouldn't rely on it. You should have redundancy backups.

Make 3 seed backups in steel washers (or titanium). And ideally encrypt them with a simple cipher (easiest and fastest) or use a passphrase and store that separately.

Earthquake proof, Low cost, affordable, easily scalable, indestructible, fireproof 1400°C (a house fire is around 1100°C), waterproof, corrosion proof, shock proof, offline cold wallet, seed or passphrase backup.

https://i.etsystatic.com/41503409/r/il/689efd/4813988559/il_1588xN.4813988559_fcds.jpg (https://www.etsy.com/listing/1434977816)
Picture taken from here: https://www.etsy.com/listing/1434977816 (https://www.etsy.com/listing/1434977816)

More information on that topic here:

https://jlopp.github.io/metal-bitcoin-storage-reviews/ (https://jlopp.github.io/metal-bitcoin-storage-reviews/)
https://incoherency.co.uk/blog/stories/diy-cryptosteel-capsule.html (https://incoherency.co.uk/blog/stories/diy-cryptosteel-capsule.html)
http://bulletproofbitcoin.com/ (http://bulletproofbitcoin.com/)
https://blog.lopp.net/a-treatise-on-bitcoin-seed-backup-device-design/ (https://blog.lopp.net/a-treatise-on-bitcoin-seed-backup-device-design/)
https://www.econoalchemist.com/post/backup (https://www.econoalchemist.com/post/backup)
https://blockmit.com/english/guides/diy/make-cold-wallet-washers/ (https://blockmit.com/english/guides/diy/make-cold-wallet-washers/)
https://bitcointalk.org/index.php?topic=5389446.0 (https://bitcointalk.org/index.php?topic=5389446.0)