Clive Thompson on Secret Messages in the Digital Age

Wired - In 440 BC, the Greek historian Herodotus first described a trick that spies used to send hidden messages. They’d write something on the wooden back of a wax tablet, then cover the message with wax bearing its own message. If enemies intercepted the tablet, they wouldn’t suspect it contained anything strange. It’s called steganography: hiding one message inside another.

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