# What is cryptography and how does it work? Interested in the history of the Zodiac killings, but have never really understood cryptography. Thanks

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What is cryptography and how does it work? Interested in the history of the Zodiac killings, but have never really understood cryptography. Thanks

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Cryptography is the science of encryption and decryption or more simply the study of how to code a message and decide it. Believe it or not, it’s a lot of math. There are tons of techniques and encoding methods, some thousands of years old. However, I’ll admit a lot of the specifics are above my head.

If you’re curious in some famous cryptography this video on the WWII German enigma code is an excellent way to get the idea of how modern encryption works. https://youtu.be/G2_Q9FoD-oQ

Basically, it’s a way to hide a message by somehow changing it into something you can change back.

For the Zodiac messages, the different symbols replaced letters and words. Complicating things, the same symbol wasn’t always used for the same letter.

An easy to implement, on a sheet of paper, rearrange the alphabet, next to the alphabet. Then look at your message. Where the message has a letter, replace it with the rearranged one. This works best when the message is short, especially if the message is also coded. So your “chicken left the roost” message becomes “xptxyu wyzm mpy gbbem” or whatever. Better is to rotate the letters after each use, so that you can’t look and try “m looks like it replaced t.” Then share the rearranged letters and encrypted message separately.

Or use numbers or glyphs or whatever.

More advanced techniques exist, but that’s where it starts.

It’s important to understand that modern cryptography goes way beyond the 5-year old children stuff Zodiak did.

With modern cryptography, the process of encryption is exactly documented, short of one short piece of information, called “key”. This key in most applications is about one page of quite large hand written text in size, or equivalent in bits.

With Zodiak, the entire process was unknown, and the cipher was created to be cracked without even knowing the cipher method. In very important ways, goals of those using cryptography and people like Zodiak are total opposites. Zodiak killer wanted his cipher to be cracked, and he presented cracking it as a game. So he would craft it more or less as a puzzle game.

People using cryptography don’t care about games, they do not want their cipher cracked, and there is this extra requirement of being able to re-use same cipher trillions of times every week using different keys, and have it always give correct message to those with key and nothing for other people.

Basically, Zodiak differs in that, there is no legit recipient to his message. It’s a puzzle game presented to investigators.