It’s a bit of math, split into two pieces.

You hand out one piece, that’s the public key. It’s tiny and simple.

You keep the other piece, that’s the private key. It’s long and complex.

The public key can scramble data that only the large piece can unscramble.

The private key can create a piece of data that only the public key can verify.

In practice, these keys can be kept in a database or a file, and they can be held in a hardware security key (yubi/fido). They can be stored on your phone, in Bitwarden, and just about anywhere that keeps passwords, they’re really just a few thousand bytes of data.

In many cases, You can store them in your phone’s private password storage, then when you log into a website, it will trigger a popup on your phone to authorize your login, so you don’t even have to keep them on the computer you’re using to access the secured site. Most of the implementations require you to have a biometric component. You need to face scan, fingerprint scan, or, worst case, use a password to unlock/verify the passkey on the device.

The upside here is that the keys are unique to every site. The public key is completely safe to hand out to everyone, it can’t be reverse engineered. This means that websites can’t leak your login credentials in any meaningful way. edit: Also since you’re using math to change a piece of data, it’s impervious to a replay attack and the communication even unencrypted would be reasonably safe even if someone was actively reading it.

As far as storing for loss, I’d consider regenerating them. I prefer using a password manager that stores them, that way my phone/computers all have access to the same keys.

You could make automatic breaking without a full blown computer, but it’s so much cheaper to put a full-blown computer than it is to do it all in hardware. Everything uses turing complete equipment now, it’s actually less expensive at this point.

There’s absolutely no reason not to put multiple computers in the car I think the real win is not surfacing it to the end user.

The first worry are vectors around the Synology, It’s firmware, and network stack. Those devices are very closely scrutinized. Historically there have been many different vulnerabilities found and patched. Something like the log4j vulnerabilities back in the day where something just has to hit the logging system too hit you might open a hole in any of the other standard software packages there. And because the platform is so well known, once one vulnerability is found they already know what else exists by default and have plans for ways to attack it.

Vulnerabilities that COULD affect you in this case for few and far between but few and far between are how things happen.

The next concern you’re going to have are going to be someone slipping you a mickey in a container image. By and large it’s a bunch of good people maintaining the container images. They’re including packages from other good people. But this also means that there is a hell of a lot of cooks in the kitchen, and distribution, and upstream.

To be perfectly honest, with everything on auto update, cloud flares built-in protections for DDOS and attacks, and the nature of what you’re trying to host, you’re probably safe enough. There’s no three letter government agency or elite hacker group specifically after you. You’re far more likely to accidentally trip upon a zero day email image filter /pdf vulnerability and get bot netted as you are someone successfully attacking your Argo tunnel.

That said, it’s always better to host in someone else’s backyard than your own. If I were really, really stuck on hosting in my house on my network, I probably stand up a dedicated box, maybe something as small as a pi 0. I’d make sure that I had a really decent router / firewall and slip that hosting device into an isolated network that’s not allowed to reach out to anything else on my network.

Assume at all times that the box is toxic waste and that is an entry point into your network. Leave it isolated. No port forwards, you already have tunnels for that, don’t use it for DNS don’t use it for DHCP, Don’t allow You’re network users or devices to see ARP traffic from it.

Firewall drops everything between your home network and that box except SSH in, or maybe VNC in depending on your level of comfort.

I’m not sure the list is really that big of a deal for a home gamer. They’re probably more in danger from their choice of home audio appliances and that microwave that has been sitting on their network for 10 years which no longer gets updates. Or that 2019 Plex server they have put forwarded straight outside.

It’s actually one of my beefs with containers, You can’t keep track of The versions for everything and you’re at the mercy of the maintainers to keep individual packages updated.