Using invisible ink to hide messages is a technique which was used several years ago. During the World War, spies used acidic liquids like lime juice to create a pattern on paper which was visible only when exposed to heat. Sometimes even much more sophisticated inks with special decoding solutions were also used for the purpose. However, when you enter the digital world, no one uses juice to write secret messages since the methods have evolved.
Researchers at the Columbia University have found a smart way to hide the text when written with basic fonts like Times New Roman and Helvetica. In order to make the text convert into an encrypted message, you will need Fontcode. The Fontcode takes a secret message, translates it into numbers and then uses the numbers to make changes in the shape or size of a single character of a font. This process cannot be performed with your eyes and the neural nets are trained to do the job for you. They will translate the modified characters back into number and then back into the original message.
The process is similar to methods which hide messages by fitting specific numbers of invisible-zero width characters in the normal letters. These methods keep the secret information while they are copied and pasted all over the web, but as soon as you get a print of them, you lose the encoded message.
With Fontcode, losing the information is not an option. Even after you take print of the message, you can still be able to view the message. The researchers behind this technology have huge ideas for its application. This can be used to embed metadata in a document. This can also be used for security or for an invisible watermark.