For example, the Da Vinci Cryptograph was commonly used in the Tang Dynasty. If the messages were retrieved in a wrong way, the letter with the white phosphorus would be self-destroyed.

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However, these self-destruction approaches could not provide sufficient confidentiality. Then the steganography technique was developed, by which the information could only be present after special treatments, like dipped in alum water, instead of being read directly with naked eyes.

In 1854, the Playfair cipher invented by Charles Wheatstone made the English alphabet frequency statistical analysis useless. This method is convenient and safe to be used, which also provides a great reference to our password books.

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Recently, two biological encryption systems built on the spores of Bacillus subtilis have been used to safely send a key and an encrypted message, respectively. Based on the previous work, we planned to establish a DNA-based information storage and transmission system of high safety using the knowledge and techniques of synthetic biology and computer science, and this time, we used yeast to achieve our goal.

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