Ooh, it might be a substitution cipher. We could start with basic cryptanalysis.

甚至有可能是替换式密码。我们可以从基本密码分析着手。

A big drawback of basic substitution ciphers is that letter frequencies are preserved.

基本替换密码的一大缺点是保留了字母频率。

This letter swapping behavior should sound familiar: it’s a substitution cipher!

这种字母交换行为听起来应该很熟悉：这是一种替代密码！

The Caesar cipher is one example of a larger class of techniques called substitution ciphers.

凯撒密码是称为替代密码的更大一类技术的一个例子。

Finally, to prevent the Enigma from being a simple substitution cipher every single time a letter was entered, the rotors advanced by one spot, sort of like an odometer in a car.

最后，为了让英格玛不只是简单的 "替换加密"，每输入一个字母，转子会转一格，有点像汽车里程表。