The alternative is symmetric encryption, but with symmetric encryption you must have a secret key known only to the parties involved in a message exchange.

另外一种方法是对称加密，但是使用对称加密时，您必须拥有只有参与消息交换各方才知道的密钥。

youdao

"And when you want to read a secret invisible message," said Sam, "you push the hair-dryer button on this part of the machine, and..."

“如果你想要阅读这条隐形的秘密。”萨姆说，“请打开吹风机的按钮吹一下，然后…”。

youdao

"And when you want to read a secret invisible message," said Sam, "you push the hair-dryer button on this part of the machine, and..."

“如果你想要阅读这条隐形的秘密。”萨姆说，“请打开吹风机的按钮吹一下，然后…”。

youdao