Advice regarding storing a Metal backup of a multisig with a bank vault

[endocrinecompacted]

I am considering storing M number of keys with different bank vaults
I plan to keep the metal backup in a serialized tamper evident bag.

I am worried about 2 things.
1.  Custodian peeping into the metal plate engravings through the serialized tamper evident bag( I dont trust the opacity of it)
2. Custodian using high end Xray machines to read through the engravings without damaging the tamper evident bag

There are lead based sleeves sold by mineracks.com, Great product, But dont want to deal with toxic materials.

Does using a 24 engraved washers, Nut & Bolt setup protect me from a custodian using High end Xray machines to peep into the metal backup without leaving a trace?

I can combat the first problem easily by wrapping the metal plates with opaque stuff and then storing it in a tamper evident bag,
but 2nd problem is high tech!

what do you guys think about the 24 washer solution and defense from high tech Xray / CT machines?
Is there any other alternatives ?

Kindly keep " You are being too paranoid" advice to yourselves

I really appreciate response to this
Thanks

[dumpsterhawk]

Your concerns are valid. This is a possible attack vector and to make it worse you will probably never be able to prove that it was the custodian unless you get lucky and he does something stupid during the theft. For this case it is best to never store the full seed phrase at any location. Instead you can use Shamir's secret sharing to split it up into several fragments depending on your budget. With this it will essentially mimic a multi-signature address setup, where you may need 2 more fragments to reconstruct the seed phrase.

https://www.ledger.com/academy/topics/security/shamirs-secret-sharing

Does using a 24 engraved washers, Nut & Bolt setup protect me from a custodian using High end Xray machines to peep into the metal backup without leaving a trace?

I don't think you will find experts here that can answer this question with correct information. That's why I skipped it and provided an alternative. What one must also consider is not today's tech, but tomorrow's tech. If you create protections that are sufficient against scanners of today, that does not mean that it will work against scanners of tomorrow. There simply isn't a set it up and forget it solution.

Kindly keep " You are being too paranoid" advice to yourselves

Next time it will help you to create your thread as self moderated.

[Callido]

I feel you are exaggerating ways to backup your wallet, you not doing wrong but you overthink security layers, it's all difficult to go through this process, one way of maximizing security is to maintain simplicity while being preventive.

If i were you, i will save my self from the whole stress, get myself a hardware wallet get my private keys out and also prepare another security layer using passphrase. There is no need of bank vaults, engraving the keys on a steel is recommendable along side not being careless with whatever aside form you choose to secure your keys, either paper form or choose to encrypt before putting down in a physical form.

[BitMaxz]

I don't think these X-ray and CT scan can penetrate thick, solid metal vault to scan what's inside, so I think your plan of hiding the metal sheet with your seed backup in a thick, solid metal vault should be fine.

I also want to recommend instead of using a metal sheet why not try the cryptosteel capsule to save your seed phrase but it's only for one seed phrase so having a multiple of these for multisig and having a silica gel in tamper evident bag would be enough for long term holding and protections.

[coupable]

Does using a 24 engraved washers, Nut & Bolt setup protect me from a custodian using High end Xray machines to peep into the metal backup without leaving a trace?

I don't think you will find experts here that can answer this question with correct information. That's why I skipped it and provided an alternative. What one must also consider is not today's tech, but tomorrow's tech. If you create protections that are sufficient against scanners of today, that does not mean that it will work against scanners of tomorrow. There simply isn't a set it up and forget it solution.

Good point. There's really no guarantee that what is invulnerable today may become invulnerable tomorrow. There's a high probability that these small metal boxes will be vulnerable to new factors in addition to natural damage. An idea crossed my mind, but I'm not sure how viable it is. What do you think about equipping the box that will store the metal plate with as many layers of protection as possible? Then, keep up with the latest updates regarding advances in printers and radiation used. Then, if we discover a new update, we can update the protective layers of that box. What do you think?

Of course, this doesn't change the fact that it remains a major risk to store all the seed words in a single copy hidden in a single location controlled by a third party.

[Darker45]

I honestly don't have any idea about the exact capabilities of the latest X-ray technologies, but isn't it ironic for one to self-custody Bitcoin yet the backup is given to a third-party custodian? Or do you keep a copy of the backup yourself and keep another copy in a bank's vault?

If you're thinking of the most secure way to hide your backup and you think it's a bank's vault, but then you're worried that the custodians might find a way to peep into it, then perhaps it's not secure to store a backup in a bank's vault?

Anyway, the impression is that this is a huge amount. You might want to consider dividing it into smaller amounts. You might not have to worry about high-end X-ray machines.

[SilverCryptoBullet]

I am considering storing M number of keys with different bank vaults

Why you want to ignore a great chance of having your own bank, being your self custodian, and want to return to banks?

Bitcoin with its private keys gives you perfect opportunity and tool to be your own bank, and if you can store your private keys safely and by yourself, you don't depend on any bank that surely never gives bank customers any keys to their bank vault including user bank money.

With either single signature or multi-sig wallet, you must do following steps that surely including "Stay away from banks or any custodians except yourself"

- Verify wallet software.
- Create your wallet offline.
- Make your wallet backup.
- Test your wallet backup for recovery.
- Fund it with small fund for testing.
- Funding it with big capital later.

How to backup a seed phrase?

[Lakai01]

I am considering storing M number of keys with different bank vaults

Why you want to ignore a great chance of having your own bank, being your self custodian, and want to return to banks?
[...]

I don't see it that way, he doesn't use traditional banking services but simply the possibility that banks offer "secure" storage of valuables. Other companies also do this, not just banks.
He is still the master of his finances, which is what the expression "be your own bank" is actually aimed at.


@OP
Have you thought about not engraving the seed correctly? For example, by swapping words and additionally storing the way in which the private key can be restored or having it stored by a notary?
My view is very similar to that of the previous poster: the technical possibilities are developing rapidly and we are always one step behind.

[m2017]

I plan to keep the metal backup in a serialized tamper evident bag.

The "serialized tamper evident bag" is not a guarantee (protection) that they will not be able to look inside. The "serialized tamper evident bag" will only have the function of an indicator that there was or was not break inside.

Also, after opening the bag and finding the contents, the outer package can be replaced with an identical one. It will not be a problem to replace.

I am worried about 2 things.
1.  Custodian peeping into the metal plate engravings through the serialized tamper evident bag( I dont trust the opacity of it)
2. Custodian using high end Xray machines to read through the engravings without damaging the tamper evident bag

There are lead based sleeves sold by mineracks.com, Great product, But dont want to deal with toxic materials.

I'm not sure the bank would allow a similar box to be placed in its vault.

You wouldn't keep this "toxic material" under your pillow, would you? So, there's no need to worry about it.

Does using a 24 engraved washers, Nut & Bolt setup protect me from a custodian using High end Xray machines to peep into the metal backup without leaving a trace?

And don't store all 24 words in one place. Divide, for example, into 2 parts and store in two different vaults in different banks. Or, keep some of the words yourself.

I can combat the first problem easily by wrapping the metal plates with opaque stuff and then storing it in a tamper evident bag,
but 2nd problem is high tech!

Wrap the seed phrase in a medical X-ray protective collar, for example.

If it is used in medicine, it can't be toxic (no direct contact with lead).

what do you guys think about the 24 washer solution and defense from high tech Xray / CT machines?
Is there any other alternatives ?

Washers are a good solution, and I described above how to protect it from X-rays.

Kindly keep " You are being too paranoid" advice to yourselves

Food for thought for the paranoid: bank employees will have questions if you pack the contents of your safe so carefully, and they may want to satisfy their curiosity.

[KiaKia]

Sorry I will never be able to trust anything that's centralised in this life anymore, this have always been me and that's why I choose Bitcoin, keeping my recovery seed on a steel and making sure this is always with me is all I care about, not in a vault of a bank somewhere else.

This idea is only considerable if I live in a country where natural disasters are like plague there, water, air and fire maybe, I am fine keeping the steel to myself and not in any bank vault.

To say the truth this is too much, going to the bank and keeping the keys in vaults because of what? It's why I will support those saying your point is too exaggerating, because it actually feels overexaggerated.

[endocrinecompacted]

With all due respect,
it could be a 3 of 5 multisig,
involving 4 different custodians vendors/ countries in different locations( Hypothetically).
So chances of each of them screwing over or coordinating is low!
reason  I might prefer this system is
1. It provides defense against rogue governmeny
2. 5 $ wrench attack
3. using different vendors of hardware wallets to defend against some backdoor that I cant think of
4. defense from calamities etc.
I have come to the conclusion of multisig after a deep analysis.

Kindly dont enforce single sig with passphrase upon me!!

Its a multisig for sure.
And I dont have 3 -5 houses ,people or secure locations to keep keys safe!
so naturally I am inclined to professional locker vault rentals!
instead of suggesting alternatives, I would really appreciate if you think of it as a puzzle and solve it for me!
1. I trust serialized tamper evident bag as a rogue locker employee cant replace with same serial number bag after tearing it thus giving me enough information that whether its compromised or not!
2. a) I just want a type of metal backup setup that will provide defense against someone peeping into metal backup without damaging the tamper evident bag( i dont trust the opacity of the bag)

   b) and defense from High end xrays and ct scanning  seeing through the engravings.

what do you guys think of 24 washers stacked on a bolt method to defend against xrays/ct?

[Cricktor]

During my university time I worked with X-ray diffraction machines and had a course to become a radiation protection officer. It's a long time ago but I know a thing or two about X-ray stuff. Clearly, diffraction machines wouldn't be suitable to peek into a metal backup as described by OP, so from that side I don't have hands-on experience to peek into opaque bags.

It's a matter of power of the X-ray source and how well your imaging detector is capable to display small deviations of X-ray transparency of your probes.

I understand the concerns OP has, but in my opinion this is way over the top. An adversary would have to take your metal backups in opaque temper evident bags and bring it to very costly X-ray equipment like the stuff used at airports or similar. All this to hide from you they could peek into your backup while remaining undetected. I don't believe this would play out like what you are concerned about.

I have no practice if airport X-ray scanners are able to actually make imprints in metal visible. If not, you would need even way pricier X-ray scan equipment. Your adversary doesn't even know if all the X-ray hassle is worth the effort, unless you brag about your Bitcoin holdings.

It's easier to rip open the bag, torture you in a 5$ wrench attack and believe me, there are ways to make humans talk.

In my opinion it's more likely you screw up your multi-sig setup or something else than some adversary scan your opaque bags with a suitable X-ray scanner. Be reasonable, the likelyhood isn't zero, but very very close to it. In a risk assessment I would put such a risk into the "not realistically going to happen" camp and thus a negligible risk not worth to cope with. It's probably more likely that you're involved in an accident which leaves you with broken memories and not remembering enough details of your redundant backup scheme. Do you have redundant and safe documentation for you or your heirs?

[Mia Chloe]

~snip

Firstly you should store your seed phrase yourself. Those stuff about X-ray detecting your seed through metal plates can only be done if you don't keep your seeds private. Basically no one will go looking for something where they didn't keep them and based off of that condition no one will attempt to make use of detectors of any kind in search of your seed if they are not aware that you have a seed there.
Security and privacy actually go hand in hand and you can't separate them. As much as you are actually trying to make sure your Seed is safe you should also make sure that your seed is private.

[Ojima-ojo]

We don't need to go this far, storing Bitcoin and having a generateble backup storage, it make sense for us to be flexible enough irrespective if how technical Bitcoin storage can be.


Let look beyond all the toughness in Bitcoin storage and achieve the most common security that we can and being able to recover them at will and as asap as possible.

[SilverCryptoBullet]

I don't see it that way, he doesn't use traditional banking services but simply the possibility that banks offer "secure" storage of valuables. Other companies also do this, not just banks.
He is still the master of his finances, which is what the expression "be your own bank" is actually aimed at.

I really disagree with you and I believe most of experienced Bitcoin users disagree with you too.

If you store your money in banks, gold in banks, bitcoin in any vaults or purchase bitcoins through Bitcoin ETF shares, you don't have your own bank. "Be your own bank" means you own your Bitcoin private keys, and only you have access to your Bitcoin private keys as well as your bitcoin.

Surely it requires you doing things right: choosing a good wallet (open source, non custodial) and practice your download, verify and install as well as wallet creation and backup well too.

[dumpsterhawk]

I don't see it that way, he doesn't use traditional banking services but simply the possibility that banks offer "secure" storage of valuables. Other companies also do this, not just banks.
He is still the master of his finances, which is what the expression "be your own bank" is actually aimed at.

I really disagree with you and I believe most of experienced Bitcoin users disagree with you too.

If you store your money in banks, gold in banks, bitcoin in any vaults or purchase bitcoins through Bitcoin ETF shares, you don't have your own bank. "Be your own bank" means you own your Bitcoin private keys, and only you have access to your Bitcoin private keys as well as your bitcoin.

You are mistaken, and it is you who does not understand what any of this means. If you store a backup of your seed phrase within some vaults, whether with a custodian (bank or company) or not (your own home or other secret location without a custodian) it is still you who owns those private keys. You are confusing two concepts that have nothing to do with each other. If you store your coins with a service such as an exchange, then you do not own the private keys for those coins. If you store your phrase or even physical hardware wallets in vaults, you are still your own bank.

You need to think about this in the proper way. If you have Bitcoin stored at your home, you can still get robbed. If you have Bitcoin stored in a bank vault, it can still be robbed. Who the robber is whether the custodian or a random criminal, does not matter. There are just different kinds of risk profiles that you need to evaluate before proceeding with this.

[Lakai01]

I don't see it that way, he doesn't use traditional banking services but simply the possibility that banks offer "secure" storage of valuables. Other companies also do this, not just banks.
He is still the master of his finances, which is what the expression "be your own bank" is actually aimed at.

I really disagree with you and I believe most of experienced Bitcoin users disagree with you too.

If you store your money in banks, gold in banks, bitcoin in any vaults or purchase bitcoins through Bitcoin ETF shares, you don't have your own bank. "Be your own bank" means you own your Bitcoin private keys, and only you have access to your Bitcoin private keys as well as your bitcoin.

You are mistaken, and it is you who does not understand what any of this means. If you store a backup of your seed phrase within some vaults, whether with a custodian (bank or company) or not (your own home or other secret location without a custodian) it is still you who owns those private keys. You are confusing two concepts that have nothing to do with each other.

Thanks for the clarification, he seems to have completely misunderstood the concept. In times of ledger leaks, where among other things the addresses of hardware wallet owners were published, one could even argue that storing the private key/mnemonic code in a safe deposit box is even more secure than storing it in a house where it is known that potentially higher crypto holdings are stored.

As I said, the whole thing has little or nothing to do with “Be your own bank”.

[m2017]

I have no practice if airport X-ray scanners are able to actually make imprints in metal visible. If not, you would need even way pricier X-ray scan equipment. Your adversary doesn't even know if all the X-ray hassle is worth the effort, unless you brag about your Bitcoin holdings.

It's easier to rip open the bag, torture you in a 5$ wrench attack and believe me, there are ways to make humans talk.

If take a random photo from the Internet, then on the X-ray of the luggage can see the well-known $5 wrench, on which the factory engraved text on the handle is slightly visible, which allows us to assume that, in theory, the text from the metal backup can be seen in this way.

But there are nuances. For example, if the metal backup is not on one plate, but several (like round washers fastened together), but I assume that the text will not be read because all the symbols on one plane will "merge" into one mess of symbols (create "noise" in the image). Also, if the washers are placed on their edge, that will also not allow reading the text from them. I want to say that in order to see your seed-phrase under the X-ray image, several factors must coincide and, if desired, the chances of this can be minimized.

After all, x-rays are used to identify prohibited items, not to read fine print on small items. If you haven't put 12\24 words on the handle of a gun or the blade of a knife, then it's unlikely that your luggage will be of interest to anyone (in the case of an airport).

[dumpsterhawk]

I have no practice if airport X-ray scanners are able to actually make imprints in metal visible. If not, you would need even way pricier X-ray scan equipment. Your adversary doesn't even know if all the X-ray hassle is worth the effort, unless you brag about your Bitcoin holdings.

It's easier to rip open the bag, torture you in a 5$ wrench attack and believe me, there are ways to make humans talk.

If take a random photo from the Internet, then on the X-ray of the luggage can see the well-known $5 wrench, on which the factory engraved text on the handle is slightly visible, which allows us to assume that, in theory, the text from the metal backup can be seen in this way.

It is risky, and the main problem is that you can't know for sure. You can't be sure whether XRAY scans are stored in any way, who has data to access them and so on. If someone does manage to read it off of the scan, you would never be 100% sure and you could not prove who the thief was and would unlikely be able to prove it. I would not carry an engraved metal piece through the airport. For this purpose the classic metal seed backups are better, as you can overlay the individual letters with each other to prevent the readout or just reassemble it on the other side from a small paper note.

With that now I wonder how easy it is to crack a seed phrase if you have all the starting letters for 24 words but without order. That would be 96 individual metal plates with letters on them. Maybe someone good at numbers could check.

[CryptoYar]

[...]

It is true that if text is clear on simple piece of metal X-ray might pick it up. However it is very unlikely this would actually happen. Your suggestion to use layered or jumbled metal pieces would make text unreadable airport X-rays are made to find dangerous items not these kind of tiny words and with so much luggage no one is looking for or would likely even spot such small details. And it is far too difficult for thieves to get our seed this way compared to other methods so unless our seed backup looks like weapon we are probably safe.