When a consumer signs up with a company that uses BlockScore, they will be asked for their name, address, date of birth, and passport number or the last four digits of their social security number. That info is then passed to BlockScore API and verified to make sure that it is real and that the person is not on any criminal watch lists. Then BlockScore asks the consumer questions to verify their identity, such as “which of these people do you know?” or “which make of car did you own in 1999?” Larger companies often request photo IDs, utility bills, bank statements, or leases to verify identity or rely on credit reporting agencies to verify identity.

http://techcrunch.com/2014/06/26/blockscore-lands-2m-in-funding-for-making-i-d-verification-easier/