It's been encrypted pretty naively, pretty simplistically, but it's actually an English sentence that's been somehow scrambled; but scrambled in a reversible way.

它被天真地，相当简单地加密了，但是它实际上是一个被加密的英语句子,但是加密方式是可逆的。

哈佛公开课 - 计算机科学课程节选

It's a secret number so that if Julius Caesar scrambled his message with the key 13, well, then the recipient had better know what that number is or realistically, -- and this is why it's kind of hard to buy -- into some of these age old algorithms, -- what would an alternative approach be to figuring out Julius Caesar's messages to his generals if he didn't know that secret number was 13?

它是一个机密的数字，以至于,如果凯撒大帝使用密钥13加密了它的消息，然后接收者最好知道那个数字是什么,实际上--这就是为什么很难,破解这些古老的算法-,有什么变换方法使凯撒大帝的将军,可以解密凯撒大帝的消息，如果他不知道,那个机密数字是13呢？

哈佛公开课 - 计算机科学课程节选

So something the Germans used on their U-boats and the output of that is a scrambled message.

德国人在他们的U型潜水艇所用到的东西的输出,是一个加密消息。

哈佛公开课 - 计算机科学课程节选