You type at the keyboard words that you want to encrypt.

你从键盘上键入你想加密的单词。

哈佛公开课 - 计算机科学课程节选

But how many of you have ever called Facebook up or called Amazon up and kind of whispered into their ear I'm going to encrypt this with the number 13.

但是有谁听过Facebook或者亚马逊,稍微低声地告诉他们,我将用密钥13加密这个消息？

哈佛公开课 - 计算机科学课程节选