Google has good feature available for Blogger blogs where one can take a back up of the blog. One has an ability to export your blog into the Blogger Atom export format. You can do this to move your blog to another blogging service or simply to store your blog on your own hard drive. Don't worry, your blog will still remain on Blogger until you delete it.
The below screenshot is for old blogger templates.
The below input is for new blogger templates and procedure is as listed below:
Login your blogger account>Template>Settings>Other>Reach Screen where you can back up blogger
Above is a screenshot of the data made available from Google and thus it is an authenticated data. You can watch the video for importing and exporting blog below: