凯撒密码作为一种最为古老的对称加密体制，在古罗马的时候都已经很流行，他的基本思想是：通过把字母移动一定的位数来实现加密和解密。例如，如果密匙是把明文字母的位数向后移动三位，那么明文字母B就变成了密文的E，依次类推，X将变成A，Y变成B，Z变成C，由此可见，位数就是凯撒密码加密和解密的密钥。个人原创。-Caesar password as one of the most ancient symmetric encryption system in ancient Rome have been very popular, his basic idea is: by the letters move a certain number of bits to achieve encryption and decryption. For example, if the key is the number of bits of plaintext letters backward move three, the plaintext letter B into a ciphertext E, and so on, X will become Y-become a B,, and Z becomes C Thus, the median is the Caesar cipher encryption and decryption keys. Personal originality.