How do we define "airgap" around here?

[goldkingcoiner]

Depending on how old the laptop is, and how much you used it, you might find data destroying viruses, bugs and faulty hardware/software could lead to a complete destruction of any Bitcoin data that you save on it.

That's what shred is for

This does not work reliably on SSDs, it works only for HDDs.

Usually it comes down to the TRIM implementation of SSD. But since there's no easy/quick way to know it works properly, people sometimes recommend to fully fill the disk with random data or use drive-level encryption (as prevention).

I was also just going off of the less techy perspective of airgap that can be attributed to the majority of Bitcoiners (I would think). I doubt they will go that far as to use shred. But LoyceV is right, making backups is without a doubt, very important. Since OP brought up the subject of preferring to use old computers, I am also talking about the physical parts. Every backup will eventually age. Meaning degradation of the disk, physically, through age and temperature and etc...

Perhaps it would be wise to make backups of your Bitcoin device every n amount of years with new devices? Old computers do seem convenient for the short term though.

[ABCbits]

people sometimes recommend to fully fill the disk with random data

That's exactly what shred does.

I forget shred also work on /dev/* directly. From what i've seen, using command such as dd if=/dev/urandom of=/dev/sda ... is more common.

Shredding individual files doesn't work on SSD due to wear leveling, but shredding the entire disk works fine: it fills the entire disk with random data (multiple times by default).

Even shredding or filling entire disk doesn't give 100% guarantee, due to feature called over-positioning (some people call it spare NAND flash/chip).

--snip--

I was just going off of the less techy perspective of airgap that can be attributed to the majority of Bitcoiners (I would think). I doubt they will go that far. And LoyceV is right, making backups is without a doubt important. But I am also talking about the physical parts. Every backup will eventually age. Meaning degradation of the disk, physically, through age and temperature and etc...

Perhaps it would be wise to make backups of your Bitcoin device every n amount of years with new devices?

Fair point. What i say is more related to prevent our data being recovered, rather than possible issue you mentioned earlier.

[LoyceV]

Even shredding or filling entire disk doesn't give 100% guarantee, due to feature called over-positioning (some people call it spare NAND flash/chip).

That's why I don't sell disks after using them, but when I get a second hand laptop, this isn't something I'm concerned about. What terrible virus is going to hide in spare disk storage and comes out when I'm running Linux?

[rightscope]

Built a computer ages ago for the company I work that only printed the same ten different documents for like a decade.
The computer never touched either the network or the internet because there is no LAN ports.

Now the computer has been given to me and I've done and offline installation of Linux and installed Bitcoin Core 31.1, everything seems to work great and obviously I cannot connect to any peers to get the first block since there is no LAN present in the machine.

Question: where can I get the first block and how can I "deliver" the first block to Bitcoin Core without any network or internet present? (I do not want to sync the blockchain on an online machine and later insert the complete blockchain into the machine in one take, I want to do this one block at the time from the very first block)

something like: $ bitcoin-cli --accept-new-block --ignore-not-connected --assume-good --trust-anyway --path-to-next-block="/media/small-device/block00001.dat"

[Cricktor]

...

What exactly are you trying to achieve with this tedious procedure, if it were possible to feed Core one block at a time? I fail hard to see the point in this.

If your premise is to keep the device all the time offline, that's a valid point. But then I would provide verified blockchain data files from an online node which has done a proper IBD, which is not what you want, for whatever reasons.

I'm asking what makes your desired method any better than just copying block data files over?

A blknnnnn.dat file contains usually multiple blocks and not necessarily in order. For more details, see https://learnmeabitcoin.com/technical/block/blkdat/

[rightscope]

...

What exactly are you trying to achieve with this tedious procedure, if it were possible to feed Core one block at a time? I fail hard to see the point in this.

If your premise is to keep the device all the time offline, that's a valid point. But then I would provide verified blockchain data files from an online node which has done a proper IBD, which is not what you want, for whatever reasons.

I'm asking what makes your desired method any better than just copying block data files over?

A blknnnnn.dat file contains usually multiple blocks and not necessarily in order. For more details, see https://learnmeabitcoin.com/technical/block/blkdat/

If my goal was to keep an updated version of the blockchain on the offline machine I assume one of the easiest routes would be to simply transfer an updated version of the .bitcoin dir to the offline machine.
I feel the need to explain that there is no specific goal I want to reach with this exercise, I am just tinkering with the program because I like it and I want to see what happens when I feed it with the very first block manually and when I have studied that I want to manually feed it the second block and so on. Also I want to figure out if it is even possible to do this because I get the feeling that others have asked similar questions in this forum and they are all getting questions why they want to do it rather than if it is possible to do it. Somehow it would make sense that it could be done since there is a way for an online machine to get a block and process it which assumes the block would be processed even if the internet connection would break during the process?

Thank you for the link you provided, that link answered some of my questions.

[LoyceV]

If my goal was to keep an updated version of the blockchain on the offline machine I assume one of the easiest routes would be to simply transfer an updated version of the .bitcoin dir to the offline machine.

To stay a bit on-topic in this thread, it's good to realize you don't need the full blockchain on your airgapped system. The airgapped system is meant to keep your keys secure, the blockchain can be updated on an online watch-only wallet.

[Cricktor]

...

To my knowledge the Genesis block is hard-coded and every node knows about it from the start, because you can't fetch it trustlessly and verify it to be genuine.

...

Exactly. The cold/offline signing wallet doesn't need an up-to-date blockchain, it doesn't need it at all. It takes an unsigned transaction via PSBT, you verify all details of the to-be-signed transaction and if all is good, you sign it with the required private keys that are securely stored in this cold/offline wallet. You then export the signed transaction as PSBT and move it to the online watch-only wallet to broadcast it.

Cold/offline storage has to remain offline to avoid any potential malicious exposure. And repetition doesn't hurt: cold storage usually doesn't need blockchain data, be it old or current.

You can play this out with a Testnet coin wallet. There are still free faucets to get enough Testnet coins to practice such stuff.

[rightscope]

To my knowledge the Genesis block is hard-coded and every node knows about it from the start, because you can't fetch it trustlessly and verify it to be genuine.

...

Say that I have synced til block 100 on the offline machine, how can I while the machine is still offline provide it with block 101?

If my goal was to keep an updated version of the blockchain on the offline machine I assume one of the easiest routes would be to simply transfer an updated version of the .bitcoin dir to the offline machine.

To stay a bit on-topic in this thread, it's good to realize you don't need the full blockchain on your airgapped system. The airgapped system is meant to keep your keys secure, the blockchain can be updated on an online watch-only wallet.

I am well aware, my question is not about what the minimum requirements are to maintain an air-gaped machine but how to manually provide an offline machine with block 101 if the machine is synced til block 100 if I wanted to.

[LoyceV]

Say that I have synced til block 100 on the offline machine, how can I while the machine is still offline provide it with block 101?

That's not how it works. But if you really want it: connect it to a fully synced offline Bitcoin Core on your offline local network, set it to sync using addnode, and use invalidateblock to prevent it from syncing block 102:

Code:

invalidateblock "blockhash"

Permanently marks a block as invalid, as if it violated a consensus rule.

Arguments:
1. blockhash    (string, required) the hash of the block to mark as invalid (code -1)

But again, you shouldn't do this. If you want to continue this quest, you should open a new topic.

[PrivacyG]

This is the type of Topic I like!

Airgap is making sure that device has no way of communicating with the external World.  Tails could be one way, but if you do not set up Persistent Storage then you are going to have to keep inserting the Seed every single time you want to use your Bitcoin.

My way is.  Purchase an older computer.  Make sure there is no way it will be able to communicate with the outside World.  No Wi-Fi, no Ethernet, no Bluetooth and other such things.  To make sure I actually do not make any mistake, I generally like to block any easily accessible USB port so that I do not accidentally plug in a flash drive.

Then install a Linux Distribution on it.  Install Electrum, get a cheap web camera and use Bitcoin through QR codes only.  Use the airgapped computer to sign transactions, use another online device to view balances and broadcast transactions.  I just imported my bc1q76xwrcslun45tt8trlklpec8kywg7f4qznwdmh as a watch only Address in to Electrum while using non persistent Tails and with out even owning it, I could prepare a transaction to send around 0.0025 Bitcoin to the public Bitcoin Talk Address of LoyceV,

Code:

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

Now I could go to my airgapped computer, import it using the QR code with the above content and sign it, then I would have to get the signed transaction QR code and import it this online computer to broadcast it.  It is a lot more complicated but being unable to connect to the external World in any way, this is the one setup that makes me feel the most comfortable.

And now it kind of feels like I turned him in to my laboratory rat for experimental purposes.  I am sorry, LoyceV!

You can even import all your transactions to the offline Electrum by QR and it will then show your updated, full balance.  Then you can create and sign transactions directly off of it and only use the online computer to import the signed transaction and broadcast.  I used to do this but after a while it got pretty exhausting so I stopped.

If you are ever paranoid about QR codes you could use an old offline phone to check the code contents before using the same QR on the online computer.

Airplane Mode and similar other Software side switches are not things to rely on.  First of all.  Even if it actually does what you think it does, as in turn Wi-Fi, Bluetooth et cetera off, you might instantly turn them back on by accidentally pressing the Fn key in combination with the right button.  Some computers do not even require the Fn key, but only the 'Airplane Mode' key instead which is even easier and worse.

[Satofan44]

My way is.  Purchase an older computer.  Make sure there is no way it will be able to communicate with the outside World.  No Wi-Fi, no Ethernet, no Bluetooth and other such things.  To make sure I actually do not make any mistake, I generally like to block any easily accessible USB port so that I do not accidentally plug in a flash drive.

Don't forget to plug the 3.5 jacks while you are at it. 

Airplane Mode and similar other Software side switches are not things to rely on.  First of all.  Even if it actually does what you think it does, as in turn Wi-Fi, Bluetooth et cetera off, you might instantly turn them back on by accidentally pressing the Fn key in combination with the right button.  Some computers do not even require the Fn key, but only the 'Airplane Mode' key instead which is even easier and worse.

Although such models are less common these days, this is why machines with actual physical switches are better for this purpose. Although removing the Wi-Fi card on most laptops is going to be fairly easy, so one might as well just take it out completely. If you like these kinds of experiments, try building a small Faraday cage and measure whether you can block all of the signals effectively.

[BlackHatCoiner]

[...]

So basically what you're describing is a SeedSigner, except that:

- you're choosing a custom Linux Distribution
- you're manually removing the hardware parts that could be used to connect to a network
- and you don't use a dice to generate the seed.

What I do like with your setup is that you don't trust the SeedSigner devs! 

[PrivacyG]

So basically what you're describing is a SeedSigner,

To be honest with you, I always thought SeedSigner was a product like a Ledger, a Trezor et cetera.  Only now that I looked it up I found out it is actually a 'Do It Yourself' airgapped wallet.  This is going to be an exciting rabbit hole to go in, particularly because I have some Pis sitting unused for many years in a box.

[philipma1957]

If I securely reinstall a barebones linux distro, or run Tails, do you folks consider this airgapped, even if at some point this computer was online?

I'd say airgapping is more about future actions than about past actions: make sure the data on it can never reach the internet in the future (including accidentally plugging in an ethernet cable).

 

Seeds are not important on an air gapped electrum server.

Passphrase is important.

As for air gapped.

Remove wifi
 remove bluetooth
Remove ethernet.

Use a USB to ethernet adapter when you end the airgap. Ie empty the wallet.

To make a clean install erase the hard drive/ssd/nvme.2,securely then load some kind of Linux i like mint.

THEN INSTALL Electrum.

Then make a 12 or 24 word seed

Copy it . Put it  on washers bla bla bla. It is not important.

Here is the important part. Buy the tiles below

https://www.amazon.com/dp/B07MBJ3DLR?psc=1&ref=ppx_pop_dt_b_product_details

Write 100 as 00 if you pull it.

Write 1 as 01 if you pull it
Write 2 as 02 if you pull it.


Pull a tile return it until you have

00,01,02,03,04,05,06,07,08,09
00,01,02,03,04,05,06,07,08,09
00,01,02,03,04,05,06,07,08,09
00,01,02,03,04,05,06,07,08,09
00,01,02,03,04,05,06,07,08,09
00,01,02,03,04,05,06,07,08,09

 this is a random 400 bit number no one is cracking it.

Your security is solid

You need be sure the electrum download is clean

You need to not attach the pc to the net via eth cable  unless you want to empty wallet.

You need to store the seed safely
You need to store the 120 digit passphrase safely.

You need to track addresses you made for deposit.

And it is air gapped until you empty it

[LoyceV]

As for air gapped.

Remove wifi
 remove bluetooth
Remove ethernet.

For the truly paranoid:

malware can leak data over an air-gap by transmitting sonic and ultrasonic signals from a computer speaker. In order to eliminate such acoustic covert channels, current best practice recommends the elimination of speakers in secured computers, thereby creating a so-called ‘audio-gapped’ system.

In this paper, we present ‘Fansmitter,’ a malware that can acoustically exfiltrate data from air-gapped computers, even when audio hardware and speakers are not present. Our method utilizes the noise emitted from the CPU, GPU, and chassis fans. We show that a software can regulate the internal fans’ rotation speed in order to control their acoustic signal

Using our method we successfully transmitted data from audio-less, air-gapped computers, to a mobile phone in the same room.

So use a fanless laptop, remove the speakers and don't have any listening devices (commonly known as phones) nearby.

[zabzob]

Another thing for the truly paranoid to worry about:

Data can be exfiltrated from a computer's screen. A surveillance van parked outside your home can reproduce the image on your screen by intercepting EMF radiation from your location. This might also be possible with keyboards, giving direct access to your keystrokes. So the only way to be truly airgapped is to use your device inside of a Faraday cage. Good luck, and stay safe.

[nc50lc]

So use a fanless laptop, remove the speakers and don't have any listening devices (commonly known as phones) nearby.

Interesting paper,
it's similar to the built-in Electrum plugin "Audio Modem" which can export/import PSBT using speakers and mic.
I never thought that the fans can be exploited using that method.

At least on desktop, there are desktop fans that can directly use the PSU's sata/molex cables to power it at max output without any control from the system.
Maybe disabling one or two pin(s) that detect and control the rpm of the laptop's fans can do something similar (for existing laptops that heavily rely on fans)

[LoyceV]

Data can be exfiltrated from a computer's screen. A surveillance van parked outside your home can reproduce the image on your screen by intercepting EMF radiation from your location.

I'd be more worried about a random attack using malware, than a targeted attack with allocated manpower.

it’s possible to “read” the wirelessly recorded EM radiation with up to 70 percent accuracy.

This might also be possible with keyboards, giving direct access to your keystrokes.

Recent studies have also shown that even wired keyboards can be exploited via the RF emanated along their cable.

So the only way to be truly airgapped is to use your device inside of a Faraday cage. Good luck, and stay safe.

At this point, just make the entire house a Faraday cage.

[Satofan44]

Another thing for the truly paranoid to worry about:

Data can be exfiltrated from a computer's screen. A surveillance van parked outside your home can reproduce the image on your screen by intercepting EMF radiation from your location. This might also be possible with keyboards, giving direct access to your keystrokes. So the only way to be truly airgapped is to use your device inside of a Faraday cage. Good luck, and stay safe.

Most users here do not have enough value to protect to justify building a big Faraday cage.   A lot of these attacks are nice theoretical proof of concepts, but there is nobody out there actually using them do accomplish something in practice. There are different possibilities, we could go on and bring out a few more research papers on what is theoretically possible.

However, if we consider what is actually realistic on the other hand, then why would someone bother with this when either a phishing attack or a wrench attack works much better? Pretty much every single non-anonymous forum user is completely exposed to both of them.