Cryptographers Solve Decades-Old Privacy Problem

We all know to be careful about the details we share online, but the information we seek can also be revealing. Search for driving directions, and our location becomes far easier to guess. Check for a password in a trove of compromised data, and we risk leaking it ourselves.

These situations fuel a key question in cryptography: How can you pull information from a public database without revealing anything about what you’ve accessed? It’s the equivalent of checking out a book from the library without the librarian knowing which one.

Concocting a strategy that solves this problem—known as private information retrieval—is “a very useful building block in a number of privacy-preserving applications,” said , a cryptographer at the University of Texas,