中国古代最早的通讯方式是使用公文，它的保密性不强，而且要用人来传递，如果这个人被敌人抓住，经不住严刑拷打，就有可能叛变，极易泄密。寻找一种安全的通讯方式成为兵家急务，于是密码诞生了。根据现有资料记载，中国古代最早发明密码通讯的人为北宋军事百科全书（武经总 The earliest means of communication in ancient China was the use of official documents. Its confidentiality was not strong, and it was transmitted by people. If this person was captured by the enemy and could not stand the torture, it would be possible to mutiny and be easily divulged. Finding a secure means of communication became a matter of urgency for the military and the password was born. According to the available information, the earliest people who invented the code communication in ancient China were the Northern Song Dynasty military encyclopedia