HTTPS Everywhere is a Firefox extension, encrypts your communications with a number of major websites. Many sites on the web offer some limited support for encryption over HTTPS, but make it difficult to use. For instance, they may default to unencrypted HTTP, or fill encrypted pages with links that go back to the unencrypted site.
The HTTPS Everywhere extension fixes these problems by rewriting all requests to these sites to HTTPS. It will encrypt all communication with several major websites.
The license of this software is Free, you can free download and free use this browser plug-ins software.