# Directions for changing a system from password-based gpg keyfile # to smartcard-based gpg keyfile # Be sure that you meet the following requirements: # 1. GnuPG >= 2.1 installed with # * Smartcard support enabled (scdaemon must be built) # * Direct CCID access built into scdaemon # 2. A password-based gpg keyfile ${KEYFILE} (e.g. "keyfile.gpg"): # That is, a file containing the slot key for LUKS, which # has been encrypted symmetrically with GnuPG using # a password. # 3. Your public OpenPGP identity ${RECIPIENT} (e.g. "3A696356") # 4. An OpenPGP smartcard holding the decryption key associated # with your public identity # 5. A CCID smartcard reader # Notes: Requirement 4. and 5. can of course be one device, e.g. # a USB token with an integrated OpenPGP smartcard # Make a backup of your keyfile (assuming it lies on the boot partition) $ cp /boot/${KEYFILE} /safe/place/keyfile.bak.gpg # Change your keyfile from purely password-based to both # password-based and key-based (you can then decrypt the keyfile # with either method). As an example aes256 is chosen, the cipher # is not important to this guide, but do note that your kernel # must support it at boot time (be it built into the kernel image # or loaded as a module from the initramfs). $ cat /safe/place/keyfile.bak.gpg | gpg -d | gpg --encrypt --recipient ${RECIPIENT} --cipher-algo aes256 --armor -c > /safe/place/keyfile_sc.gpg # Verify that you can decrypt your new keyfile both with the password # and your smartcard. # (with smartcard inserted, you should be prompted for your PIN, unless # you already did so and have not yet timed out) $ gpg -d /safe/place/keyfile_sc.gpg # (with smartcard disconnected, you should be prompted for your password) $ gpg -d /safe/place/keyfile_sc.gpg # After verification, replace your old keyfile with your new one $ su -c 'cp /safe/place/keyfile_sc.gpg /boot/${KEYFILE}' # Export your public key to where crypt-gpg can find it $ gpg --armor --export-options export-minimal --export ${RECIPIENT} > /safe/place/crypt-public-key.gpg $ su -c 'cp /safe/place/crypt-public-key.gpg /etc/dracut.conf.d/crypt-public-key.gpg' # Rebuild your initramfs as usual # When booting with any of the requirements not met, crypt-gpg will default to password-based keyfile unlocking. # If all requirements are met and smartcard support is not disabled by setting the kernel option "rd.luks.smartcard=0" # crypt-gpg will try find and use a connected OpenPGP smartcard by prompting you for the PIN and then # unlocking the gpg keyfile with the smartcard.