@everyone as part of spring 17 Lightning components can be added to unauthenticated sites using lightning out. below is the link

https://releasenotes.docs.salesforce.com/en-us/spring17/release-notes/rn_lightning_apps_public.htm

"Add the 'ltng:allowGuestAccess' interface to your Lightning Out dependency app to make it available to users without requiring them to authenticate with Salesforce." Technical implementation details are mentioned in the above link.

@everyone as part of spring 17 Lightning components can be added to unauthenticated sites using lightning out. below is the link

https://releasenotes.docs.salesforce.com/en-us/spring17/release-notes/rn_lightning_apps_public.htm

"Add the ltng:allowGuestAccess interface to your Lightning Out dependency app to make it available to users without requiring them to authenticate with Salesforce."

Technical implementation details are mentioned in the above link.