It is not often that you get an SEO tip directly from Google. But, last week Google officially announced that they are now including whether sites use secure, encrypted connections as a signal in their search ranking algorithms. However, Google says that this update will not have a large effect on search results:
For now it’s only a very lightweight signal — affecting fewer than 1% of global queries, and carrying less weight than other signals such as high-quality content — while we give webmasters time to switch to HTTPS.
This change reinforces Google’s stance on keeping user security a top priority, which has already been seen in their other services (Search, Gmail, and Google Drive) which automatically have a secure connection. Read the full article on the Google Webmaster Central Blog Official Google Webmaster Central Blog: HTTPS as a ranking signal.