An Opinionated Yubikey Set-Up Guide | Hacker News Reader

An Opinionated Yubikey Set-Up Guide

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143 pointsjustinludwig72 comments

The excellent guide by drduh should be mentioned here: https://github.com/drduh/YubiKey-Guide — I've been using this approach for years to store my OpenPGP keys on Yubikeys and use them for SSH.

I don't generate my keys on devices. That lets me be flexible and keep backups, as well as use the same keys on multiple physical devices. Using a single yubikey is a bad idea, as you're bound to eventually lose it or break it. Hasn't happened to me yet in 5 years, but I expect it to happen.

I wish more sites supported hardware keys instead of only TOTP tokens, or (heaven forbid, but corporate idiocy is plentiful) SMS.

I've been using his guide forever as well, except that nowadays you can just use the native OpenSSH support for deriving Ed25519 or ECDSA keys from FIDO. The main advantage is that you do not have to deal with the very subpar GPG Agent anymore... https://www.maths.tcd.ie/~fionn/misc/fido_ssh/

Besides, 1Password now has a very convenient agent, which prompts users permission for an application to use a key - which is added security https://developer.1password.com/docs/ssh/get-started/#step-4...

And yes, Yubikeys do break - My keychain'd 5Ci is missing a huge chunk of plastic, exposing the PCB, and among the two new C Bio I received last week, one has already fried after just a few days.

It’s super good!

I love my Yubikey - it’s way less friction to use than other forms of 2fa, and I get to use it for stuff like storing my PGP keys. I don’t feel like it use it to its full potential (mostly signing commits and ssh) but it’s super satisfying seeing that little “Verified” badge next to my signed commits :)

I do generate them on device, I just have multiple Yubikeys. Of course there's a significant cost there, but OpenPGP cards are a good backup and cheaper.

Yep, thats the same guide I used a few years ago as well!

I use it daily for Github/ssh in general - and the 2 slots are used for part of passwords for a couple of other things.

I have a couple that are used daily, one in a safety deposit box (which is the "master" key), and a stack of new ones on my desk in case anything breaks. (I used that Cloudflare offer to get a hefty discount on them).

I also have a paperkey copy that lives elsewhere.

I feel like leaving the "backing up" section of this till last is burying an important part of realistic threat analysis here: i.e. the risk of losing access to data from losing, accidentally destroying, or a malfunction of your Yubikey is substantially higher then the risk of compromise.

If you set all this up, then it would be an expected outcome that the most likely thing you'll be doing is needing to recover from a disaster, not prevent a compromise.

>or a malfunction of your Yubikey

Can't stress this enough. I had a yubikey nano that I literally never pulled from my laptop, that sat on my desk for basically the entirety of COVID. It just up and died after about 14 months. Fortunately, I had only set it up for testing purposes because I was worried about this exact scenario, and while I had a backup in my safe, had I been on my normal travel schedule that wouldn't have helped much.

The fact that it died after 0 abuse was a MAJOR turnoff for me ever proceeding down the path further. I'm sure my failure was a one-off but it left an extremely bad taste in my mouth.

I get a failure of a key that's on a keychain or being beaten up on the regular, but failure from literally just sitting in a usb-c port for less than two years is... not a great look.

I guess this might be an expected failure mode too, because their warranty is only 1 year for manufacturing defects.

On the flipside, I’ve had a Yubikey 4C for around 4 or 5 years on my keychain in my pocket, and it’s holding up OK.

Backup is a serious question though. I once started down this rabbit hole trying to type up a guide for using my yubikey and I found myself giving up when I realized there was no perfect solution.

I have Yubikey nano in my laptop, desktop, and Linux PC. All of them are still going strong. I have four Yubikeys on my keychain, two of which I bought in 2014, and they also are still working without issues. None of my keys have ever failed.

Think about it this way: forcing electrons through a circuit is abuse. Since they bumble around like flowing honey looking for the easiest way out.

Yubikeys are well constructed. I don’t think they die frequently before several years.

I can't stress this enough, risk of losing (or breaking) your security keys is the number 1 threat when a service (correctly) offers no way to circumvent it's absence.

This is the same for encryption: the number 1 threat is lost encryption keys; the number 2 threat is broken backups; the number 3 threat is stolen encryption keys. Having #1 occur is equivalent to being ransomwared with no way to pay.

In both cases, you need multiple copies, or if you are using non-copyable aspects of security keys like U2F or OTP, then you need multiple backup keys registered to the same services.

It's for this reason that I eventually decided upon pencil+paper secrets in a bank safety deposit box, which can be backed up or even split up in a 2/3 fashion for things super critical.

The yubikey ends up being solely for convenience for less important things(it's easier to press the yubikey physically than it is to bring out my google authenticator app and copy/paste a TOTP).

Agreed that the article goes into extreme technical depth from a security/cryptographic perspective, whereas losing/breaking/being_stolen is actually the vastly more likely scenario.

> It's for this reason that I eventually decided upon pencil+paper secrets in a bank safety deposit box

This is not an option for the vast majority of people. But While we are at it, if the government wants to confiscate your bank locker they totally can and have access to all your secrets. So then what do you suggest?

> This is not an option for the vast majority of people

A bank SD box costs $50/year. Why is this not an option for a majority of people? If anything, it's more accessible to use a bank SD box than being a technical enough person to run code from a GitHub repo.

> But While we are at it, if the government wants to confiscate your bank locker they totally can and have access to all your secrets. So then what do you suggest?

The bank SD box isn't full proof (as any bank employee could take a peek), which is why you'd want to shard the secret into multiple SD boxes. I.e. if your secret is ABC, you could store three secrets of AC + AB + BC, wherein you need only 2/3 to recover the entire secret. This scheme is effectively the same as Shamir Secret Sharing, but way easier to recover.

If your threat level is that the government might confiscate your bank locker, then you're probably at the level that you'd want geo-distributed sharded secrets in privacy-centric countries like Switzerland.

This is interesting, never heard of Bank SD box and the way you describe distributing the secret is novel. Do you have any links to a practical implementation?

The government can totally take and use your Yubikey as well.

Or often also just ask the service that you’re protecting a login for for your data directly.

If you're using a service.

But there are actual setups where storage can be encrypted with a Yubikey, and the Yubikey is protected by a PIN that's in your head, and other possible factors, so now we're in $5 wrench territory.

Yeah the only thing that can beat the $5 wrench is plausibly deniable encryption + training to pass a polygraph.

Very few people have this threat level and the will power to go that far.

And all YubiKeys die it is just a question of when.

> This is the same for encryption: the number 1 threat is lost encryption keys

This is so true. I worked on v1 of BitLocker. Key management was a much bigger feature than the actual full-disk encryption. I only recently got a Yubikey because I know how easy it is to shoot myself in the foot, and I’m still very nervous about it.

Agreed. Turns out the best backup medium is paper: print out the secret bits and store them in a safe. The paperkey tool can do this and QR codes can make it really convenient. I even added binary decoding interfaces to zbar to support this exact use case.

https://www.jabberwocky.com/software/paperkey/

https://wiki.archlinux.org/title/Paperkey

  gpg --export-secret-key $KEY | paperkey --output-type raw | qrencode --8bit --output $KEY.png
  zbarcam --raw --oneshot -Sbinary | paperkey --pubring $KEY.gpg | gpg --import

Not every key needs to be backed up. Signing keys are ephemeral, losing one is inconsequential. Losing an encryption key means it'll be impossible to decrypt data later so backups could be interesting. The master key should be kept permanently offline in a physical safe.

Like the other comments, the risk of losing data/access/etc is not enough.

The article even actively suggesting you DO NOT make backups of things.

    Now you’re ready to generate a new set of OpenPGP keys on the YubiKey, using the generate command:

        gpg/card> generate
        Make off-card backup of encryption key? (Y/n)

    Enter n to ensure that the private keys never leave the YubiKey, and enter the admin PIN when prompted:

I suppose this is why it's an Opinionated guide as my opinions on how the actual target of a "remote adversary" should go about balancing security with risk.

Yeah, if you're paranoid about the key being stolen when generated, just unplug the network, boot a live DVD image, store it directly to a USB stick, and then unplug the USB stick before rebooting.

I usually don't go through quite so many steps, so if my machine was already actively compromised when I generated my keys, then the attacker has my keys.

The simple solution is to buy two, or more. Mind you, Yubi could be more upfront about the risk and the solution. But it's pretty obvious pretty quick that if your access depends on a single physical key that one key isn't enough.

I don't enable Yubikeys unless I can assign at least two to my account.

It's that simple. Yubi should just be a bit more transparent about the need for two or more.

I have this same discussion about people using Vault and having secret unseal keys.

If you're all in on the idea and have a robust process around key custody it's great, but if you just deploy it without thinking especially to an environment that may not be fully rebooted for 1-2 years at a time, it's far more likely someone will lose the keys and then only months or years later when the entire thing is restarted realise they lost all their data. And I'd put this as more likely than encryption at rest ever saving most people from data privacy.

You have to include availability and user experience in your "threat model".

I was gifted a Yubikey about a month ago, and I planned to use it as 2FA instead of having to open up Google Authenticator 10-20 times a day and copy 6-digit codes.

It took a little effort to set up, but now it's working as intended. And I didn't realize it, but every time I had to pull out my phone and enter one of those stupid 6-digit codes, I was grinding my teeth! It was just such an annoying little chore. My mouth feels so much more relaxed now that I just tap the little button on the Yubikey.

I also set up the long-press functionality to store a static password, and that has been the cherry on top.

I would consider PIV and SSH through PIV/OpenPGP legacy and undesired nowadays. If you're only interested in state of the art second factor instead of passwords for sensitive use cases, a simple FIDO2 security key w/o all the extra features on a yubikey 5 is enough.

You can solve most of those with only FIDO2 nowadays:

Webauthn with fido/u2f is supported on most websites and oidc providers.

SSH with FIDO and resident / non-resident keys is supported.

PAM -> as documented in the guide, although setting origin and type manually isn't necessary and you can save keys in ~/.config/Yubico so non-root users can manage their keys. I would recommend enabling PIN verification with pamu2fcfg --pin-verification.

LUKS hard disk encryption with FIDO2 for unlocking isn't covered but is possible, systemd-cryptenroll can set this up on modern linux distributions.

| Webauthn with fido/u2f is supported on most websites and oidc providers.

I wish that was true. I’ve found that webauthn is becoming more common in the last year, but is still relatively rare. Many “important” sites and services make use of them. https://www.yubico.com/works-with-yubikey/catalog/ is a great place to see them, but they’re still quite rare as a whole.

The author's idea that writing down your unlock codes and PINs on paper is an acceptable/reasonable backup system is, I think, a bit wishful, and quite impractical for most people.

I recommend getting 5 Yubikeys, generating unique PGP keys on all of them, then storing two offsite in different locations, such as your vacation home or safe deposit box or office. Three are for your keychain and one each for your desktop and laptop or two laptops.

Then, PGP encrypt your text file with all of these details to all five keys.

I have two Yubikeys (a primary and a backup) in each of two safe deposit boxes in different states (4 total), one on my keychain, and one nano in each of my 5 computers. I encrypt my long term data to 10 recipient keys.

Threat model aside, I think expecting people to maintain multiple PGP keys, do multi-key encryption, and geographically distribute those keys is probably less practical than writing their pin down.

99% of users are probably better served by Tarsnap and its ilk than attempting to roll this kind of thing themselves.

Eleven years ago I got four yubikeys, two pairs as recommended by Yubico. One pair for personal use and one for work.

I tested the personal key pair first. The primary yubikey I had on my (physical) keyring failed spontaneously after less than three weeks of being carried around in my pocket. That was the end of that.

I am not going back to physical tokens, except for RSA tokens and purely mechanical keys. Those have an adequate track record.

I have four Yubikeys.

One of them is a black one that work gave me for use with the work computer. I’ve had this Yubikey for over 1 year.

Three of them are blue ones I bought from Amazon, that I also added to my SSO profile at work. I’ve had these Yubikeys for several months.

One of them I keep in my wallet most of the time. One of them I keep on my desk and bring in my backpack when I go somewhere. One I keep in a box. One is somewhere in the room.

I rotate between these, and I switch which one I keep in the wallet, which one I keep in a box etc.

It’s worked well for me so far. None of them have failed yet, and when one does fail or get lost I will remain confident that the other ones I have will continue to work long enough that I can order even more Yubikeys to replace which ever ones went bad.

Yeah, if you want to be a charity donating to Yubico, godspeed. Not my cup of tea.

Yubikeys are $50. Ten are $500. Mine protect keys that can decrypt data worth hundreds of millions of dollars.

My $500 worth of Yubikeys has lasted me 5 years and counting, so we're at <$10/month TCO. That's to have 10 of them.

Data worth hundreds of millions of dollars? What’s an example of data that an entity would realistically pay hundreds of millions of dollars for? The only thing that comes to mind would be the database backups of user data of a large company’s software, which is literally irreplaceable if lost (but then infinity is larger than one hundred million…)

I am the co-founder of Keyternal.

https://keytern.al (website painfully out of date)

I estimate the hundreds of thousands of cryptocurrency private keys we safeguard (in conjunction with the keys held in other organizations, via multisig) have at points in time protected somewhere on the order of single digit billions USD.

We're not a wallet provider, just a backup key storage service, so I couldn't get exact figures even if I wanted to: by design we don't have that information about our customers.

The PGP-encrypted keys are held completely offline (cold) in vaults, the set of Yubikeys (in other, different vaults) is used during signing ceremonies to temporarily decrypt them (only in ram, on offline computers without storage) to produce recovery signatures when our customers run out of other options. We're the last resort in a DR plan.

It requires careful coordination with another keyholder (a different organization) to produce valid transactions; neither ours nor theirs alone is sufficient. Transactions need two signatures: one from each. In that sense, neither key is "worth" anything by itself, but together they protect large sums.

What happens when someone that stores their keys with you pass away? Do you have contact details for who in their family to reach out to, to help them recover the money of the deceased person?

I have a lot of yubikeys. The one I still use the most is my first one: the rfid enabled that isn't even on their history pages. It's been on my keys for more than 10 years and I wouldn't say it looks new but not very much unlike the 5s it's next to. Neither has ever failed me.

I have around 4 Yubikeys on my (physical) key ring. I purchased two of them back in 2014. None of my keys have ever had an issue.

For me the track record has been perfect.

You've got the wrong perception of even the most sophisticated end-users out there. 5 GPG keys, deposit boxes / vaults in different states.. I mean what the hell? Even an old beardy maintainers won't be bothered by that. You're talking about government-level threat models here.

Heck, even the idea of having to renew your resident GPG keys is a nightmare, let alone in different states. If you even let your master key expire on the device, you won't ever be able to renew it or it's derived SSH keys, and will have to reset the device. That's not to mention fried keys, stolen keys, etc. Consumer-grade vaults can be picked in minutes, and most large banks do not issue new deposit boxes anymore.

Any paranoid/sophisticated users would be more than happy with having their SSH keys in 1Password & using their agent, or having one key at home w/ home alarm, one key on them.

> You've got the wrong perception of even the most sophisticated end-users out there. 5 GPG keys, deposit boxes / vaults in different states.. I mean what the hell? Even an old beardy maintainers won't be bothered by that. You're talking about government-level threat models here.

You seem to misunderstand me.

They're not in vaults for protection from the government; the state can access them at will. They are in vaults for fire safety.

They are in multiple states for safety against natural disasters. If one bank floods or is destroyed, a copy exists elsewhere.

Each vault has two Yubikeys, to protect against fried keys. Two locations in case one is stolen, etc.

It's not about threat model, it's just about DR.

> Any paranoid/sophisticated users would be more than happy with having their SSH keys in 1Password & using their agent, or having one key at home w/ home alarm, one key on them.

Storing the keys in software makes them vulnerable to software malware, which is ridiculously common. No "paranoid" required.

Most people are at home most of the time. If one key is at home and one key is "on [you]" and your house burns down, you lose all your keys and all your data so protected.

It's not some state-sponsored attacker that requires you to keep an extra key offsite in a fireproof room.

5 Yubikeys? That's fine if you're really serious about this, but to me even one Yubikey is too expensive for personal user.

Most people don't have a vacation home, or a safe deposit box. I didn't even think you could still get those at most banks. Plus, I suspect most security conscious people would not want to leave anything at their office.

You can leave them at friends houses, but that's not exactly always a secure location.

Phone numbers can at least theoretically be recovered, so my unpopular opinion is that SMS is pretty great for personal stuff.

Five whole YubiKeys at the cost of $500+ sounds extortionate when memorizing your Ed25519 private key is a free option.

How do you keep your keys up to date? Or, if you need to onboard a new key because you lost one, how do you know it's been registered with all your services?

I don't know what you mean by "up to date". The keys do not change.

I don't lose keys.

When I get new accounts, I simply enroll each of the keys in each computer, plus my keychain key, in the U2F for the new account. This doesn't happen often due to SSO.

But that means you have to go out of state to enroll the keys you have in storage there. Not exactly practical.

Although I think that for the general (ie not ultra-critical) U2F use-case, not having all the keys enrolled is acceptable, if you're able to log back in without them, say by using codes stored encrypted with the GPG keys of all the others.

Oh, only the computer (and keychain) keys are used for U2F. There is one 24/7 resident in each computer (the C Nano variant) and an extra on my keyring. Each of these also has a PGP key.

The 4 in the vaults are only used for PGP.

I have a script that will PGP encrypt a file to all 10 of the Yubikeys. I keep track of all of the fingerprints and pubkeys in spreadsheet.

Neat, but this too hard I think. Have used a key with websites and that is doable for a regular (or busy) person. The rest of this should be done by the OS, through a wizard, at install time and/or later. Maybe a control panel app.

Nits:

- Model: Ideal device is 5C.

- GPG: S key should not also be C. The point is the C key should be the root of S, E, and A so they can be expired, revoked, and rolled individually.

- NFC: Disable it or don't buy it. It's a wide attack surface. USB-C works with iPads and Android devices, iPhones <= 14 with an adapter, and iPhone >= 15.

- Backup & recovery: Contrary to YK doc, there are too many issues with multiple card-generated YK secrets and identifiers for practical use. Create an identical device (apart from card no) with a 2nd YK kept offsite in secure physical storage by loading secrets to both rather than generating them on-card. It's possible to do so securely on a trusted machine (say running Tails or Qubes OS on a physical new machine without internet).

- Reset PIN: It's foolish to not create one.

- FIDO2: Setup your own (deprecated but still works) private, firewalled behind NAT server from https://developers.yubico.com/u2fval/

- Linux and Mac workstations: Setup gpg-agent ssh-agent compatibility instead of the PIV method because it doesn't require their custom PKCS#11 module with an unproven security track record. And update the firmware with the Yubikey Manager app.

What would be the ideal suggestion for a Yubikey setup -- where I’m not hounded by authorities, don’t want to act out the James Bond lifestyle, and am just an ordinary person interested in extra security for him and his family?

I want to be able to have Yubikeys for (i) my primary desktop at home, (ii) my travel Laptop & other devices (iii) backup (at least two) if any of the primary ones fail. Rinse and repeat for each family member.

My suggestion for a regular person is to not deal with Yubikeys. The risk of me somehow shooting myself in the foot trying to use them is much higher than the risk of getting hacked. My most important thing by far is my bank account, which has 2FA via the Chase app on my phone. Doesn't even support Yubikeys. A few other things are like this.

That's good enough for my personal life. I only use a key at work, where they manage all that for us.

If you travel overseas a Yubikey (or equivalent) is apparently a good way of escaping the account lockouts that Google applies when it detects suspicious behaviour. While TOTPs and regular passwords can travel a continent in a few milliseconds, a hardware key cannot, so anyone using it overseas is much more likely to be you.

I've yet to test this but adding a hardware key is the advice I've found online around this particular issue.

(Yes, I also have my own domain in the case I get fully locked out, I am paranoid)

For purposes of Fido/U2F, almost every service that lets you use U2F will also let you set up TOTP, and with TOTP you can save/print the QR codes. And TOTP is good enough to let you enrol a new U2F key.

So you don't need the expense of buying multiple yubikeys if most of them will end up in safety deposit boxes. Just put a printout of a TOTP QR code in the safety deposit box.

(This doesn't apply if you want to use the non-U2F features of the yubikey, like PGP, but who needs that?)

Use the "FIDO (both U2F and FIDO2 flavors)" capability to protect your Gmail account. You don't want your email compromised.. it's the most important.

Next, use 1password with the family. It too has FIDO support.

You could buy "nano" keys for each computer and just leave them installed all the time. And the backup would be one on your keychain. This is how I do it.

I'm not really that concerned about someone gaining physical access to my system compared to how concerned I am about someone on the Internet gaining access to my passwords somehow. Of course I look the doors to my house and don't leave my laptop just lying around :)

I need such a guide as well. If I want to sign up for a new service and use the yubikey as a factor is it required that I have all of them including the backup keys at hand to register them or can I keep them outside the house ?

I was looking for a cheaper alternative than Yubikey etc - then I found token2.

Their FIDO U2F costs only 5 euro.

Now I can say to people I talked to that they no longer have any reason not to use security key.

https://www.token2.com/shop/product/token2-t2u2f-security-us...

I feel like convenience is an important part of making security keys work effectively. These are definitely cheaper, but once you move out of the large bully USB-A keys to those that might not require adapters, might be smaller, more useful with things like NFC, they get a lot more expensive. Still cheaper than Yubikeys, but similar ballpark. I’m not sure this would change the maths on whether to use a security key or not for that many people?

So... I just save my 2FA stuff in keepass... Works fine and can be backed up and replicated for free vs needing several yubikeys.

This works until you get malware on your workstation.

That’s why you assign all of them random names which are recorded in a separate BitWarden store. That one only opens with a password which is “YUBIKEY”.

One can use the TPM so at least the secrets can't be mass exported. Doesn't stop keylogging individual ones of course (but a browser extension might).

I'm totally confused by the "backing up" section.

> The best back-up is the buddy system: make sure at least one other person has an equivalent set of credentials for every application for which you use your YubiKey.

Why is this the best option? How is it even a good idea at all? We're talking here about someone you deeply trust, I assume? I have a second Yubikey which is accepted everywhere my primary Yubikey is. Why is that the second-best option and not the best option? I must be missing something basic here. Can someone help me out?

The issue is something could happen to you and if your PIN is lost, it doesn't matter how many second Yubikeys you have.

Seems like this advice assumes you're using your Yubikey to protect data you want to outlast you?

Oh I see. Yeah that maybe applies to a small subset of the things I use my Yubikey for, but fair enough.

Might also want to check out https://github.com/FiloSottile/yubikey-agent as a very simple way to setup a yubi-key as an ssh-agent.

What vendors for hardware keys would be recommended besides yubico? Isn't it a bit risky when there is mainly one (known) vendor for hardware keys? Or is this just the wrong impression that you get from HN?

There's no alternative with the same set of capabilities: Fido2, OpenPGP, PIV all in one. For the individual capabilities there's many alternatives.

Why is the adversary assumed to be female?

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