Repo / key of Skype [duplicate]
Solution 1:
The problem is that after installing skype using its deb installer, it will add skype's repositories into your sources file, after adding a repository to your sources, you should add its public key too, however it seems that Skype did not add its public key to your system so you should add it manually:
As here states:
curl https://repo.skype.com/data/SKYPE-GPG-KEY | sudo apt-key add -
If you don't have curl:
wget -O - https://repo.skype.com/data/SKYPE-GPG-KEY | sudo apt-key add -