Google last week announced that it had enabled SSL encryption on international search sites.Using HTTPS by default for users logged in. This type of security was introdcued over a year ago by Google for google.com and now is being implemented on all of Google’s search pages. Google has said that feature will be pushed out to more Google search pages over the next few weeks. They also wished that this will encourage other companies to adopt SSL more broadly across there websites as well.
Source: Inside Search(Google Blog)