Packages cannot be authenticated

WARNING: The following packages cannot be authenticated!

sudo apt-get install  gstreamer1.0-pulseaudio

Reading package lists... DoneBuilding dependency tree     
Reading state information... DoneThe following packages were automatically installed and are no longer required:  libdirac-encoder0 libopencore-amrnb0 libopencore-amrwb0 libsvga1 libvo-aacenc0 libvo-amrwbenc0Use 'apt-get autoremove' to remove them.The following NEW packages will be installed:  gstreamer1.0-pulseaudio0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.Need to get 57.6 kB of archives.After this operation, 220 kB of additional disk space will be used.WARNING: The following packages cannot be authenticated!  gstreamer1.0-pulseaudioInstall these packages without verification [y/N]?

To solve:

sudo apt-key update $ sudo apt-get update  

Related:

sudo apt-key list
sudo apt-key remove FBB75451
sudo apt-key list