Invisible ink was known as "sympathetic stain" during the Revolutionary War. By any name, it was an effective spying tool.
Vlogger Reuben Levine tells the story of the Colombian army in 2010 sending a message to prisoners of a revolutionary guerilla group by hiding a Morse code message in a concocted pop song. Watch this ...
An anonymous bidder has won the solution to a 35-year-old puzzle for nearly $1 million. The top-secret code could be used to solve Kryptos, an infamously enigmatic sculpture containing four hidden ...
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