anchor.diff:                description = "Whether to use a passphrase and a Yubikey (true), or only a Yubikey (false)";
               };
   
  +            multiUser = mkOption {
  +              default = false;
  +              type = types.bool;
  +              description = "Whether to allow multiple users to authenticate with a Yubikey";
  +            };
  +
               slot = mkOption {
                 default = 2;
                 type = types.int;
  
positive.code:         mount -t ${yubikey.storage.fsType} ${toString yubikey.storage.device} ${yubikey.storage.mountPoint}
  
          local uuid_r
          uuid_r="$(take 32 ${yubikey.storage.mountPoint}${yubikey.storage.path})"
  
          local uuid_luks
          uuid_luks="$(cryptsetup luksUUID ${device} | take 36 | tr -d '-')"
  
          local k_user
          local challenge
          local k_blob
          local aes_blob_decrypted
          local checksum_correct
          local checksum
  
          for try in $(seq 3); do
  
              ${optionalString yubikey.twoFactor ''
              echo -n "Enter two-factor passphrase: "
              read -s k_user
              ''}
  
              challenge="$(echo -n $k_user$uuid_r$uuid_luks | openssl-wrap dgst -binary -sha1 | rbtohex)"
  
              k_blob="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
  
              aes_blob_decrypted="$(drop 32 ${yubikey.storage.mountPoint}${yubikey.storage.path} | hextorb | openssl-wrap enc -d -aes-256-ctr -K $k_blob -iv $uuid_r | rbtohex)"
  
              checksum="$(echo -n $aes_blob_decrypted | drop 168)"
              if [ "$(echo -n $aes_blob_decrypted | hextorb | take 84 | openssl-wrap dgst -binary -sha512 | rbtohex)" == "$checksum" ]; then
                   checksum_correct=1
                   break
              else
                   checksum_correct=0
                   echo "Authentication failed!"
              fi
          done
  
          if [ "$checksum_correct" != "1" ]; then
  
negative.code:             local new_k_blob
              new_k_blob="$(echo -n $new_challenge | hextorb | openssl-wrap dgst -binary -sha1 -mac HMAC -macopt hexkey:$k_yubi | rbtohex)"
  
              local new_aes_blob
              new_aes_blob=$(echo -n "$k_yubi$k_luks$checksum" | hextorb | openssl-wrap enc -e -aes-256-ctr -K "$new_k_blob" -iv "$new_uuid_r" | rbtohex)
  
              ${optionalString yubikey.multiUser ''
              sed -i -e "s|^$user_id_hash$user_record|$user_id_hash$new_uuid_r$new_aes_blob|1"
              ''}
  
              ${optionalString (!yubikey.multiUser) ''
              echo -n "$new_uuid_r$new_aes_blob" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
              ''}
          else
              echo "Warning: Could not obtain new UUID, current challenge persists!"
          fi
  