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

There isn't a single answer for this.

Encryption will always consume more CPU. This can be offloaded to dedicated hardware in many cases, and the cost will vary by algorithm selected. 3des is more expensive than AES, for example. Some algorithms are more expensive for the encrypter than the decryptor. Some have the opposite cost.

More expensive than the bulk crypto is handshake cost. New connections will consume much more CPU. This can be reduced with session resumption, at the cost of keeping old session secrets around until they expire. This means that small requests from a client that doesn't come back for more are the most expensive.

For cross internet traffic you may not notice this cost in your data rate, because the bandwidth available is too low. But you will certainly notice it in CPU usage on a busy server.