How to compute with data you can't see

Not long ago, hackers stole about 40 million debit- and credit-card records from Target, another 56 million records from Home Depot, and nearly 5 million patient records from hospital operator Community Health Systems. And this past June, personal information about millions of federal employees was taken from the U.S. Office of Personnel Management. These are just a few thunderclaps in the perfect storm of cyberattacks and data breaches making headlines recently.