During the 1920s, the German military came to learn exactly how successful the British had been

at decrypting their coded messages during the First World War.

And this led them to search for a more secure way to send coded messages.

By the Second World War, they had what they believed to be a system

for sending coded messages that could not be broken. It was called Enigma. Welcome to the history

of the 20th century. Episode 339, The Enigma Machine.

Today, we are going to talk about cryptography and cryptanalysis, or to put it in plain English,

writing messages in code and breaking the code to read the message, respectively.

One simple way of encoding a message is by substituting letters.

For example, you might decide to change every A in your message into an H,

every B in your message into a Y, and so on,

until you have a table in which each and every letter of the alphabet is assigned

to its own unique code letter. If you write your message using the code letters, it will come out as

gibberish. Other people will not be able to decipher your message unless they have a copy of the table

that tells them which

code letter represents which letter in the message.

And I already know what you're thinking. It is, in fact, possible to decipher such a message

without a copy of the table. In fact, in the United States, there is a daily syndicated newspaper feature called

crypto quote, which consists of a saying from a well-known person coded in exactly this way,

which is offered to the reader as a puzzle to solve. You can also buy puzzle books that include cryptograms for you to decipher,

and you can find web pages and apps that offer you cryptograms to solve for your entertainment.

If people are doing cryptanalysis of this kind of code for recreation,

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