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。
"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…”。
Thus I want to make a gift to you of this Mysterious Secret Message.
因此，我想把这个神秘的信息作为礼物送给你。
Thus I want to make a gift to you of this Mysterious Secret Message.
因此，我想把这个神秘的信息作为礼物送给你。
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