I was happy when the announcement was made on Blogger Buzz yesterday that Google is now extending HTTPS to just like their other products such as G-Drive,Google search e.t.c.
In case you are unaware of the importance of HTTPS:
it makes it harder for bad actors to steal information or track the activities of blog authors and visitors, it helps check that visitors open the correct website and aren’t being redirected to a malicious location, and it helps detect if a bad actor tries to change any data sent from Blogger to a blog visitor.

Once enabled, your blog will become accessible over both HTTP and HTTPS connections. authors should be aware that if they choose to encrypt at this time, some of the current functionality of their blog may not work over HTTPS.

TO ENABLE :
Simply log into https://www.blogger.com, click on the blog you’d like to make HTTPS enabled, navigate to the Settings page, and select "yes" for "HTTPS Availability". Unfortunately, blogs with custom domains are not supported in this first version.

NOTE : The new HTTPS support dose not support costume domain yet. i.e https://www.yourblog.com(not supported), https://yourblog..com(supported)

Thanks for d update