HTTP vs HTTPS performance

Question

Are there any major differences in performance between http and https? I seem to recall reading that HTTPS can be a fifth as fast as HTTP. Is this valid with the current g

Answer 1

I made a small experiment and got 16% time difference for the same image from flickr (233 kb):

http://farm8.staticflickr.com/7405/13368635263_d792fc1189_b.jpg

https://farm8.staticflickr.com/7405/13368635263_d792fc1189_b.jpg

Of course these numbers depends on many factors, such as computer performance, connection speed, server load, QoS on path (the particular network path taken from browser to the server) but it shows the general idea: HTTPS is slowser then HTTP, since it requesres more operations to complete (SSL handshaking and encoding/decoding data).