An idea came to my mind about using encryption only for sensitive data while transferring data.
Here's an example: When opening a web page you can see a lot of stuff that's accessible to other users. But a small portion of information on a website is user specific which needs to be protected. You send and receive this data through protected channel, all other are redirected to normal channels (non protected).
With that we can have less overhead that's caused by encryption.
Is this feasible and secure? Has this already been done?
EDIT: I understand from the comments that using two channels is a bad idea. I got another idea: You secure the non sensitive data with computational less demanding crypto algorithm. With sensitive data you use computational more demanding algorithm which provides better security. The data is send trough a single channel.