Difference Between Cryptography, Cryptanalysis, Cryptology

We hear a lot of terms with the word “crypt”.

Cryptography.  Cryptanalysis.  Cryptology.

The Greek meaning of crypto is hidden.

I wish it meant change, because it is more appropriate when dealing with crypt-xxxxxx.

Change to the way a message is encoded.

Change to the way a message is decoded.

And even change to the way changes have occurred to the way it has been encoded an decoded.  Let’s take a look at an example.

Caesar Cipher

The Caesar Cipher is a simple monoalphabetic substitution cipher.

Monoalphabetic means it uses only 1 alphabet.

Polyalphabetic means it uses 2 or more alphabets.

Caesar Cipher works by taking a letter, going two spaces to the left of the alphabet, and using that as the substitute letter.

Officially, the Caesar Cipher shifts THREE spaces to the left, but this is not the example we are using.  We are using 2 spaces.

So A becomes C, B becomes D, C becomes E….

crypto terms

A B C D E F G H – Plaintext

C D E F G H I J   – Ciphertext

GCUA, TKIJV ?

Difference Between Cryptography, Cryptanalysis, Cryptology

Cryptography – Study of Hiding Messages

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To define cryptography for the Caesar Cipher, it would be the study of the monoalphabetic substituion cipher.  It would be the study of how this cipher encrypts messages.

It is also a study of the history of the cipher.  A study of the Roman leader Julius Caesar himself, and why he chose this particular cipher.  Maybe because it was one of the first ciphers, and decrypting it would be unbeknownst to anybody else?  Did only Julius Caesar know how to decrypt the cipher?

Cryptography is basically a study of the way the message is hidden, and a history of the cipher.

Cryptanalysis – Study of Breaking Messages

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This one is easy to remember.

In terms of cryptanalysis, it is the study of how to crack the code!

Think NSA, Anonymous, or World War 2 intelligence agents trying to find ways to decode the German Enigma machine.

Today it seems like cracking the Caesar cipher is child’s play, but maybe not so much back in the past.

In short, cryptanalysis is the study of breaking codes.

Cryptology – The Math Behind Hiding and Breaking Messages

Cryptology is the study of MATH!

This may or may not excite you as much as it does me.  I find the use of giant math numbers in order to encrypt information around us just amazing.

Don’t get me wrong, I SUCK at math.  But it’s still cool to learn.

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Cryptanalysis deals with studying the math behind the cipher and way the messages are encrypted or decrypted.

For the Caesar Cipher, it is the study of a single alphabet and the number of spaces used to determine the key of the cipher.  Today it would be an easy challenge.

But if you were studying say the Diffie-Hellman algorithm, then it would be the study of the mathematical functions of discrete logarithms.  Pretty challenging.

You need to perform a cryptanalysis before you can do a study of a cipher’s cryptology.

Cryptology is the study of the study of cryptography and cryptanalysis.

Summary

Cryptography – Study of encrypting messages

Cryptanalysis – Study of decrypting messages

Cryptology – Study of the mathematics behind encryption/decryption

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