For thousands of years, if you wanted to send a secret message, there was basically one way to do it. You’d scramble the message using a special rule, known only to you and your intended audience.

The original version of this story appeared in Quanta Magazine. For thousands of years, if you wanted to send a secret message, there was basically one way to do it. You’d scramble the message using a ...

We may receive a commission on purchases made from links. Have you ever gotten a key copied in a sketchy store hoping to save a few bucks, only to realize that it doesn't fit the lock that well?

My sister got locked out of her house for the third time in six months last spring. She called from her porch, frustrated and embarrassed, waiting for a locksmith to charge $200 for ten minutes of ...