Unlocking LUKS with NitroKey/Yubikey: FIDO2, HMAC-SHA1, or OpenPGP? (thebrainbin.org)

submitted 2 days ago by modem_down@thebrainbin.org to c/linux@lemmy.ml

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Which approach do you think is better, and why?

Or do you think there is an even better way to use a hardware security token to unlock drives having LUKS full disk encryption?

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[-] modem_down@thebrainbin.org 2 points 1 day ago

Progress report 1

I'm ruling out HMAC-SHA1, because:
- Plain vanilla HMAC-SHA1 uses a shared secret. I don't want the PC/server to have a copy of the credential. May also be susceptible to MITM/relay attacks.
- Rolling-code HMAC-SHA1 only partially solves those problems.
- Encrypted rolling code HMAC-SHA1 solves those problems, but I haven't found a reliable source for using it with LUKS.
If using systemd, pick FIDO2:
- Avoids flaws of HMAC-SHA1.
- Native support in systemd, so "future-proof".
- Wider support than OpenPGP. More HST vendors to choose from, including cheaper options than NitroKey or Yubikey: useful if each sysadmin (or colleague, or relative) needs an HST.
- Compatible with QubesOS.
Otherwise, OpenPGP:
- Like FIDO2, solves HMAC-SHA1 flaws.
- However:
  - smartcard-key-luks seems unmaintained on GitHub and on GitLab.
  - LUKS with OpenPGP isn't well-documented for non-Debian-based distros.
TBD: Clevis/Tang:
- Remote/network-based unlocking.

[-] utopiah@lemmy.ml 2 points 1 day ago

https://support.nitrokey.com/t/unlocking-luks-volume-with-nitrokey-3-on-debian-12-2/5553/15 could be useful too

[-] modem_down@thebrainbin.org 1 points 1 day ago

Thank you for this! That thread is helpful in itself, and also links to other relevant resources - including by Lennart Poettering (controversial guy, but the canonical source on systemd).

[-] eldavi@lemmy.ml 1 points 2 days ago

wouldn't doing this require that building a ram disk image with the yubikey software included?

[-] kayohtie@pawb.social 5 points 1 day ago

All 3 mechanisms are native to a yubikey, and do not require yubikey-specific software/drivers to function as they use USB standards like FIDO2, keyboard for HMAC, and PIV/CCID for OpenPGP.

FIDO2 is built-in out-of-the-box, HMAC just requires adding the key to HMAC on slot 1 or 2 (tap vs long-hold key-inputs) using the personalization tool, or using gpg(2) to card-edit for OpenPGP.

None of these require YK software to operate.

[-] modem_down@thebrainbin.org 2 points 2 days ago

Which of the 4 recipes I posted are you referring to as "this"?

[-] eldavi@lemmy.ml 2 points 2 days ago

read them and you will see that only ones mentions initrd at all.

[-] modem_down@thebrainbin.org 2 points 2 days ago

I read them before writing my OP. I'm still not sure what you're getting at.

I would be grateful if you could say what you mean, instead of initiating an oblique guessing game.

[-] eldavi@lemmy.ml 1 points 1 day ago

instead of initiating an oblique guessing game.

i don't understand the hostility.

i asked a question about needing yubikey software in a ramdisk image to enable decryption at boot time and most of the sources you provided don't mention it at all.

[-] floquant@lemmy.dbzer0.com 3 points 1 day ago

It's not mentioned because it's not required, yubikeys in general mostly leverage pre-existing "smartcard" facilities

[-] kkremitzki@lemmy.ml 4 points 1 day ago

i don’t understand the hostility.

Bystander observation: you were asked to clarify but essentially refused in a way that took more effort than simply doing so.

[-] eldavi@lemmy.ml 1 points 1 day ago

Oic. They didn't understand that I was asking a question and thought that I was addressing one of their links

Thanks for helping clarify.

this post was submitted on 31 Jul 2026

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