凯撒密码的过程,再用配对字母取代讯息里的原始字母位移加密法(shift cipher)：模数计算。Ek(x)=(x+k)mod 26，Dk(y)=(y –k)mod 26 如：k=5 “hello world”加密为：mjqqt…. -Caesar the process of password, and then matching the letters to replace the original message encryption letters displacement (s