The origin of the number nine can be traced back to ancient civilization. In ancient Egyptian civilization, the number nine was regarded as a mysterious and sacred number, because nine was the product of three groups.
In ancient China, the number nine was also given a special meaning. According to the Book of Changes, the number of yang is odd, the number of yin is even, and nine is the pole of yang, so the number nine is regarded as an auspicious number. Some religions and myths and legends also involve the number nine. For example, the Jewish tradition holds that the number nine represents perfection and sacredness.
The magical characteristics of the number nine are manifested in many ways. In the traditional culture of China, nine is the extreme number, and it is the extreme number of yang, so it has the reputation of "the respect of the Ninth Five-Year Plan".
In mathematics, nine is an important number, which can be expressed as the square of three. Is the largest multiple of 3, and has a special status. Jiugongge is also a classic application of the number nine, which is a game of filling numbers in nine squares, and it is the basis of many intellectual games.
Decimal system is a counting system based on 9, which is widely used in some fields. For example, in computer science, decimal is used to represent the conversion between binary and decimal, because the cardinal number of nine is consistent with the number of fingers, so it is easier to do manual calculation. In some encryption algorithms, hexadecimal is also used. This binary system is simpler and more efficient in dealing with some complex problems.
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In cryptography, the number 9 is usually used to generate various complicated passwords. For example, there is a cryptographic algorithm called Vigenere, which consists of 26 letters and 27 symbols, of which 26 letters represent 26 English letters and 27 symbols represent different numbers and special characters.
In this cryptographic algorithm, each letter or symbol can be encrypted and decrypted by adding a fixed offset, which is a key composed of a group of 9 letters.
Some modern cryptographic algorithms also use the concept of the number 9. For example, there is an encryption algorithm called "cube cipher". The process of encryption and decryption is to divide plaintext or ciphertext into several small cubes according to certain rules, and then perform specific transformation and displacement operations on each cube. The security of encryption algorithm depends on the number of cubes and the complexity of transformation and displacement operations. These parameters are also set based on 9.