密码学用于什么领域？要学什么科？需要什么条件？

不一定
越战时中国不用浙江温州人的温州话做密码吗

用于政府信息加密、用于军事、商业、金融的保密通信，用于分析外太空信号的解密、分析自然界与古迹信息的内容规律。
The next generation keyboard, future keyboard!
challenge and subverting the global computer keyboard, keyboard music instruments in 25 years ago，
The pioneer of the Chinese people firstly entered this area. who sent it into the modern house of CEO of Microsoft?
To challenge AT&T of the United States by improving communication deficiencies
Improving communication deficiencies, Chinese people challenge AT&T of the United States.