“This is going to cause a huge shift in consumer use of the Internet,” said John Clippinger, co-director of the Law Lab at Harvard’s Berkman Center for Internet and Society in Cambridge, Massachusetts. “There’s going to be a huge bump and a huge increase in the amount and kind of data retailers are going to have.”

Most companies have separate systems for signing on to e- mail accounts or conducting secure online transactions, requiring that users memorize multiple passwords and repeat steps. Under the new program, consumers would sign in just once and be able to move among other websites, eliminating the inconvenience that causes consumers to drop many transactions.