Researchers have developed a rewriteable paper coating that can encrypt secret information with relatively low-tech invisible ink -- water. A message printed out by a water-jet printer on a ...

In this challenge, I used a Smiggle Spy Pen to draw a full doodle using invisible ink that only appears under UV light! 🔦🖊️ Drawing without seeing the full lines in real time was tricky—but the ...

Coded messages in invisible ink sound like something only found in espionage books, but in real life, they can have important security purposes. Yet, they can be cracked if their encryption is ...