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Show HN: Qrkey – Offline private key backup on paper

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Re: Show HN: Qrkey – Offline private key backup on paper

#21

Tangential, but why is there a docker image for a simple command line tool like this? Surely a git clone is enough, especially for a Go app, no?

Some people prefer to manage (or simply test) CLI tools, as simple or complicated they are, with Docker. You can setup an alias like 'alias qrkey=docker run --rm ghcr.io/techwolf12/qrkey:0.0.1' and run it as it was normally installed. In this example, as the image is created from scratch, the size would only be marginally bigger than the executable.

Re: Show HN: Qrkey – Offline private key backup on paper

#22
Nice, I'll add to the list of similar thing I made, specifically for keepass.

You tag entries in your keepass DB with "safe-print", then point the tool to the db file, unlock it, then it generates a printout to put in your safe.

https://github.com/kardianos/safekeysheet

Re: Show HN: Qrkey – Offline private key backup on paper

#23

Something similar, but encrypted, is PaperAge [1]. Admittedly, I haven't used it, but it seems like a nice solution for secure physical backup of small secrets. The catch, of course, is now you need to make sure you never forget your passphrase or back that up off-site somewhere else. [1]: https://github.com/matiaskorhonen/paper-age

Something similar again is my little tool hemlis [0]

It uses Shamir's secret sharing algorithm to generate shares where the private key is split in n shares with k needed to reconstruct it. The bytes are encoded as word on a PDF (either 'burnt in' or written manually with pen to minimise the risk of storing them on printers etc).

That way you can spread the risk of loosing the physical key, while still maintaining some assurance that e.g your friends can run away with the key (or be compelled to hand it over to some threat actor).

[0]: https://github.com/filleokus/hemlis

Re: Show HN: Qrkey – Offline private key backup on paper

#24
post #15

How safe is printing a private key, considering potential vulnerabilities in the printer software, firmware, and its online connectivity?

You're posing a good question but, if you look at things from this perspective, then every time you type the password to decrypt your private key you should worry about the possibility of some software running on your machine reading it and sending it somewhere.

While you pose a valid concern, I think most people don't have to worry about this. The reason is that printing private keys isn't a common practice, so I think it's unlikely that nation-states mandate backdoors in printer firmware to collect private keys, and most people don't have to worry about targeted attacks.

EDIT: On a second thought, your comment reminded me of that creepy time many years ago when a printer randomly regurgitated a partial print of a document I printed some time before (read: days or even weeks before), clearly showing that the printer kept it somewhere in memory. So it still possible that some printers memorize what you print. IIRC it was a Brother printer. At the end of the day, you can't account for every possible attack vector. Pick a reasonable threat model and act accordingly.

Re: Show HN: Qrkey – Offline private key backup on paper

#25

> Recover from a PDF with QR codes with a barcode scanner Barcode scanners scan bar codes, not QR codes.

Many barcode scanners these days can scan QR codes. I have a NetumScan NSL5 that I got for €30 or so that can handle QR, DataMatrix, and even Aztec codes.

Re: Show HN: Qrkey – Offline private key backup on paper

#26
post #2

What is the benefit of using a QR code over just printing and storing the document itself in a human-readable format? I'm trying to think of when/why I would want to add the extra step of converting to/from QR codes for the documents I keep in my safe, but I'm not coming up with any reasonable use case. I'm sure I could just be missing the use case(s) the author has in mind, perhaps they should be suggested in the re…

Error correction?

Yep, if I'm using a physical medium like paper I want to allow for some degradation. Here's a Veritasium video on QR codes: https://youtu.be/w5ebcowAJD8

Re: Show HN: Qrkey – Offline private key backup on paper

#27
post #24
post #15

How safe is printing a private key, considering potential vulnerabilities in the printer software, firmware, and its online connectivity?

You're posing a good question but, if you look at things from this perspective, then every time you type the password to decrypt your private key you should worry about the possibility of some software running on your machine reading it and sending it somewhere. While you pose a valid concern, I think most people don't have to worry about this. The reason is that printing private keys isn't a common practice, so I th…

This certainly applies to office printers. Printers that accept new jobs while printing have to store them somewhere. There have been many incidents of finding old documents on disposed printers because it doesn’t occur to anyone to wipe them first. This especially applies to “copiers”, because a copier is just a printer in the same box as a scanner.

Re: Show HN: Qrkey – Offline private key backup on paper

#29
post #27
post #24

Earlier quoted context omitted.

You're posing a good question but, if you look at things from this perspective, then every time you type the password to decrypt your private key you should worry about the possibility of some software running on your machine reading it and sending it somewhere. While you pose a valid concern, I think most people don't have to worry about this. The reason is that printing private keys isn't a common practice, so I th…

This certainly applies to office printers. Printers that accept new jobs while printing have to store them somewhere. There have been many incidents of finding old documents on disposed printers because it doesn’t occur to anyone to wipe them first. This especially applies to “copiers”, because a copier is just a printer in the same box as a scanner.

There was a conspiracy theory that China was buying old office printers/scanners hoping to recover secret documents remaining in the cache. Plausible, but seems like a lot of effort hoping for a diamond in the rough when I expect 99% of prints are boring day-to-day information.

Re: Show HN: Qrkey – Offline private key backup on paper

#30

I keep meaning to do something like this in combination with Shamir’s secret sharing (which allows you to split a secret into M blocks, of which any N can be combined to recover the key, and M and N are configurable) to distribute a private key among family members in case of my untimely demise so they can more easily access my financial accounts and stuff. Has anyone done that before, and if so, what tools do you pr…

Codex32 allows you perform Shamir secret sharing operations and error correcting code without using a computer. Instead, you can perform the operations by hand using cardboard code wheels called volvelles.

It is a really fun idea and does not require deep technical knowledge to operate. The intent is for Bitcoin secret keys, but it can be used for any secrets.

https://secretcodex32.com/

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