Can you encrypt data more than once?

A simple example is accessing a website while you are on wifi. The website itself can offer either an unencrypted connection ("http") or an encrypted one ("https", which uses SSL/TLS to hide the data being transferred. Independently, a wifi connection encrypts everything with some scheme like WPA2.

So if you connect to an HTTP site, your webbrowser will encrypt the data using SSL/TLS, your computers wifi driver will encrypt the encrypted data using WPA2, your wifi router will strip off the WPA2 encryption and send the SSL/TLS stream to your internet provider and eventually the remote website, and their web server will decrypt the SSL/TLS.

/r/askscience Thread