SAN FRANCISCO — Yahoo has added more layers of security in its effort to shield people’s online lives from government spying and other snooping.

The measures announced Wednesday include the completion of a system that encrypts all information being transmitted from one Yahoo data center to another. The technology is designed to make the emails and other digital information flowing through data centers indecipherable to outsiders.

Search requests made from Yahoo’s home page are also now automatically encrypted, and the Sunnyvale, Calif., company is promising to make it more difficult for unauthorized intruders to hack into other services, including video chats, within the next few months. Yahoo strengthened the security of its e-mail in January.