Well this is for sure a noob question, so I decided to put it here than in security
I've been a faithful Slacker for more than 5 years, but now I installed a linuxmint on my laptop.
Using synaptic pm to install glade specifically, I've been warned that I cannot check authenticity, and this could result to malicious blah blah blah...
What's up about it? Are there issues we must have in mind before installing, tricks, etc?