pps_core: module verification failed: signature and/or required key missing - tainting kernel

pps_core taints the kernel:

# dmesg|grep -i4 taint
[ 1.370203] Write protecting the kernel text: 6356k
[ 1.370257] Write protecting the kernel read-only data: 2644k
[ 1.370260] NX-protecting the kernel data: 5932k
[ 1.388264] systemd-udevd[90]: starting version 204
[ 1.441543] pps_core: module verification failed: signature and/or required key missing - tainting kernel
[ 1.441754] pps_core: LinuxPPS API ver. 1 registered
[ 1.441759] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <email address hidden>
[ 1.441991] PTP clock support registered
[ 1.458240] ahci 0000:00:1f.2: version 3.0

Can this be corrected?

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: linux-image-3.11.0-12-generic 3.11.0-12.18
ProcVersionSignature: Ubuntu 3.11.0-12.18-generic 3.11.3
Uname: Linux 3.11.0-12-generic i686
ApportVersion: 2.12.5-0ubuntu1
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: lightdm 1522 F.... pulseaudio
Date: Wed Oct 9 15:01:03 2013
HibernationDevice: RESUME=UUID=765ea940-a006-4825-a979-c4ec48d81572
InstallationDate: Installed on 2013-10-08 (0 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release i386 (20130424)
MachineType: Acer Extensa 5230
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-12-generic root=UUID=5a5a0960-705c-4925-88fa-bcb05eb87c12 ro crashkernel=384M-2G:64M,2G-:128M noquiet nosplash
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-3.11.0-12-generic N/A
 linux-backports-modules-3.11.0-12-generic N/A
 linux-firmware 1.116
SourcePackage: linux
UpgradeStatus: Upgraded to saucy on 2013-10-09 (0 days ago)
dmi.bios.date: 10/30/2009
dmi.bios.vendor: Phoenix Technologies LTD
dmi.bios.version: V1.36
dmi.board.name: Homa
dmi.board.vendor: Acer
dmi.board.version: Rev
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvrV1.36:bd10/30/2009:svnAcer:pnExtensa5230:pvr0100:rvnAcer:rnHoma:rvrRev:cvnAcer:ct10:cvrN/A:
dmi.product.name: Extensa 5230
dmi.product.version: 0100
dmi.sys.vendor: Acer