How people secured their secrets before encyption

Centuries before encrypted texts and secure video conferencing, people relied on physical engineering to keep their written messages sturdy, sealed, and secure against eavesdroppers.

In a new book, researchers Jana Dambrogio and Daniel Starza Smith outline the “letterlocking” techniques used by figures from Queen Elizabeth I to poet Emily Dickinson to protect their paper letters—and the methods Dambrogio, Smith, and a growing number of other scholars have developed to reverse-engineer those historic documents...