在第二次世界大戰結束之前，人們研究的方向是如何以更多的替換以及位移來防止密碼字典或加密機制外洩，但增加更多的替換以及位移勢必會增加進行加密以及解密的難度，也會增加操作員失誤的可能，因此當時的德軍發明了進行加解密專用的機器 — — 「謎」。
「謎」式密碼機，或稱啞謎機、恩尼格瑪密碼機，在1940年代被德軍大量使用。「謎」有著幾個重大的進展，除了用機器來取代人力進行運算以外，另一個重點在於密碼已經沒辦法單純用觀察單字的方法解回來了。（Wikipedia：恩尼格瑪密碼機）
Before the Second World War ended, the direction of people's research was how to use replacement and displacement to prevent password dictionary or the leakage of encryption mechanism, but increasing more replacement and displacement is bound to intensify the difficulty of encryption and decryption, as well will increase the possibility of operators making mistakes, therefore the German military at the time invented a special machine dedicated to decryption, that is called -- "Enigma".
The Enigma machine was used broadly by the German military in the 1940's. "Enigma" had a few major advancements, in addition to using machines to replace manual operations, another main point is that passwords are no longer decryptable simply using observations of words or vocabulary. (Wikipedia: Enigma machine)
二戰後計算機（也就是電腦）與電子學的發展促成加密方式的改變。由於電腦可以對任何儲存在其中的資料加密，且多數電腦的加密都是在二進位字串上操作，不像古典密碼學是直接作用在原始字母、數字，以語言學為基礎的破密術因此失效。
不使用頻率分析來破解一個訊息需要知道目前是使用何種加密法，因此才會促成了諜報、賄賂、竊盜或背叛等行為。直到十九世紀學者們才體認到加密法的演算法並非理智或實在的防護。
The advancements of the World War II calculator, (aka the computer) and electronics caused changes in the ways of encryption. Since the computer may encrypt any saved documents, plus most computers encrypt based on binary string, unlike classical cypher which used original letters, numbers, and linguistics-based decryption, therefore, failed for that.
To not use frequency analysis to crack a message, you must know what kind of encryption method used currently, thus brought about activities of spying, bribing, burglary, or betrayal. Only until the Nineteenth century where researchers finally understood that the operational analysis of encryption was irrational or gave actual protection.
