Why not use HTTPS for everything?

Question

If I was setting up a server, and had the SSL certificate(s), why wouldn\'t I use HTTPS for the entire site instead of just for purchases/logins? I would think it would make

Answer 1

For high latency links the initial TLS handshake requires additional round trips to validate the certificate chain (including sending any intermediate certificates), agree on cipher suites and establish a session. Once a session is established subsequent requests may utilize session caching to reduce the number of round trips but even in this best case there is still more round trips than a normal HTTP connection requires. Even if encryption operations were free round trips are not and can be quite noticable over slower network links especially if the site does not leverage http pipelining. For broadband users within a well connected segment of the network this is not an issue. If you do business internationally requring https can easily cause noticable delays.

There are additional considerations such as server maintenance of session state requiring potentially significantly more memory and of course data encryption operations. Any small sites practically need not worry about either given server capability vs cost of todays hardware. Any large site would easily be able to afford CPU /w AES offload or add-on cards to provide similar functionality.

All of these issues are becoming more and more of a non-issue as time marches on and the capabilities of hardware and the network improve. In most cases I doubt there is any tangable difference today.

There may be operational considerations such as administrative restrictions on https traffic (think intermediate content filters..et al) possibly some corporate or governmental regulations. Some corporate environment require data decryption at the perimeter to prevent information leakage ... interference with hotspot and similiar web based access systems not capable of injecting messages in https transactions. At the end of the day in my view reasons for not going https by default are likely to be quite small.