Progress report 1

• I’m ruling out HMAC-SHA1, because:
  • Plain vanilla HMAC-SHA1 uses a shared secret. I don’t want the PC to have a copy of the credential. It may also be susceptible to MITM/relay attacks.
  • Rolling-code HMAC-SHA1 only partially solves the problems of ordinary HMAC-SHA1.
  • 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:
  • It avoids the flaws of HMAC-SHA1.
  • It’s supported natively in systemd so should be “future-proof”.
  • It’s a more widely-supported standard, than OpenPGP, with more HST vendors to choose from, including cheaper options than NitroKey or Yubikey. This could be useful in environments where each sysadmin (or colleague! or family member!) needs an HST.
  • It’s compatible with QubesOS.
• Otherwise, OpenPGP:
  • Like FIDO2, it solves the HMAC-SHA1 flaws.
  • However:
    • smartcard-key-luks seems to be unmainted both on GitHub and on GitLab.
    • Unlocking LUKS with OpenPGP isn’t well-documented for non-Debian-based distros.
• TBD: Clevis/Tang:
  • Permits remote/network-based unlocking.