Steganography is a technology and science about information hiding. The so-called information hiding refers to not letting anyone know the transmission event or content of information except the intended recipient.
Invisible ink, digital watermark and letter frequency are all principles of steganography.
Bacon cipher is a kind of steganography invented by Francis Bacon. The encryption principle first converts each letter in the text into a set of five English letters. The conversion table is as follows: for example, the plaintext "ILOVEYOU" is converted into abaaababbabbabbabbabbabbabbababababababa.
The third party knows neither the existence of secret information nor the existence of secret information. Therefore, keys, digital signatures and private information can be transmitted safely in an open environment, such as the Internet or intranet. This paper mainly introduces the basic principle and various applications of steganography.