Invisible Ink is taken to the next level as a digital file with “Wizard of Oz” text hidden inside the letter.

AUSTIN, Texas— Invisible ink was taken to the next level after scientists hid a digital file with text from “The Wonderful Wizard of Oz” inside ink on a letter. They say the results of their experiment are reliable enough for the method to be used by anyone who wants to hide secret messages in letters or plastic objects.

With recorded information now almost entirely digitized, more and more people are looking to use digital encryption to keep their messages hidden and private. This requires a digital key to lock and unlock the information so that only the intended recipient can read it. Encryption uses algorithms to scramble information that can only be revealed by entering the correct code, such as a PIN or password.

Researchers have developed ways to store encryption keys in polymers, which are long chains of molecules, called monomers, linked together. They can be man-made, as in plastics, or natural, like DNA helices. The problem is that the longer the polymer, the more difficult it becomes to determine what information is stored in it.

So chemist Dr. Eric Anslyn and his colleagues at the University of Texas at Austin have developed a method to decode polymer information sequentially so that it can be read more easily. The process involves the use of liquid chromatography-mass spectrometry (LC/MS) – a method of reading chemical information.

A molecular encryption key was embedded in the ink (left image) of a letter (right image), which was mailed and scanned to decrypt a file. (Credit: adapted from ACS Central Science 2022, DOI: 10.1021/acscentsci.2c00460.)

The researchers wanted to see if their method would reveal a complex key stored in a unique blend of polymers hidden inside ink that would then be used to reveal a text file. First, the chemists generated a 256-character binary key that could encrypt and decrypt text files when entered into an algorithm. They then coded the key into eight polymers each made up of 10 monomers, the molecules that bind together to form polymers.

The eight coded pieces of information had to fit together in the correct order to unlock the binary key, and instructions on how to do this were stored in a monomer at the end of each polymer. Then the researchers mixed these eight polymers together and devised a step-by-step method of reading the polymers using LC/MS which, when followed, would reveal how they were originally designed and render the information codes available.

Finally, a group of researchers combined the polymers with soot and two colorless liquids – glycerin and isopropanol – to make an ink which they used to write a letter to other scientists who did not know the information. coded.

These scientists extracted the ink from the paper and followed the same sequence analysis created by Dr. Anslyn and his colleagues to reconstruct the 256-character binary key. When they entered this key into the algorithm, they found a plain text file of “The Wonderful Wizard of Oz”.

The research is published in the journal AEC Core Sciences.

Reporting by South West News Service editor Danny Halpin.

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