1. ## Cryptanalysis 101

Bear with me, this is my first one!  To start, I better explain why we aren’t reading up on cryptology and studying cryptanalysis instead.  Technically cryptology is the study of encrypting messages into a form only readable by the person who holds the key.  Cryptanalysis is the study of breaking the encryption and being able to read the message.  In most cases we will not be given the key or the key is hidden from us, by applying cryptanalysis we can either reveal the message or gain further insight into what the key may look like.  Either way we succeed in reading the message.  A message that hasn’t been decoded and is in readable form is referred to as plaintext while the encrypted message form is called ciphertext.  The ciphertext is the form we will be studying to search for recognizable patterns and help in deciding what sort of encryption or cipher is being used.  A cipher is the process of encrypting a message.

The focus of our study and the most basic encryption forms are the simple substitution ciphers.  These ciphers use a symbol, number or another letter to replace a single letter in the message.  That symbol, number or letter is a constant throughout the cipher and will not change.  For example if the plaintext 'E' = the ciphertext 'Y', every Y throughout the ciphertext will represent the E, always.  I will first introduce the most easily recognized ciphers so if one happens to cross your path, you already have the key and do not need to waste the time trying to crack it.  After that we will be looking at the methods to deciphering and cracking simple substitution ciphers.

The common substitution ciphers that replace a one letter for another letter are the shift cipher (also called the caeser cipher,) Atbash cipher, and the mixed alphabet cipher.  The shift cipher simply translates the cipher alphabet any number of spaces to the right (shift of one to tweny-six.)  Here is an example of a shift cipher by using the key 'shift of two':

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z      = plaintext
Y  Z  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X      = ciphertext

which turns the phrase 'this is fun' into 'rigq gq dsl'

An Atbash reverses the ciphertext alphabet, looking like this:

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z     = plaintext
Z  Y  X  W V  U  T  S  R Q  P O  N  M  L  K  J  I  H  G  F  E  D  C  B  A     = ciphertext

turning the phrase 'this is fun' into 'gsrh rh ufm'

The mixed alphabet cipher takes it one step further, usually using no or a very sporadic pattern in assigning letters.  This type of cipher can be commonly found in your Sunday paper's cryptograms or cryptoquotes.  A mixed alphabet cipher will look similar to this:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z = plaintext
H F Y U I Z D A R W M V B P C E J X G L N K O Q S T = ciphetext

*To be continued....*

2. Originally Posted by Nitefyre
A &#194;quackB &#194;quackC &#194;quackD &#194;quackE &#194;quackF &#194;quackG &#194;quackH &#194;quackI &#194;quackJ &#194;quackK &#194;quackL &#194;quackM &#194;quackN &#194;quackO &#194;quackP &#194;quackQ &#194;quackR &#194;quackS &#194;quackT &#194;quackU &#194;quackV &#194;quackW &#194;quackX &#194;quackY &#194;quackZ &#194;quack &#194;quack &#194;quack= plaintext
Y &#194;quackZ &#194;quackA &#194;quackB &#194;quackC &#194;quackD &#194;quackE &#194;quackF &#194;quackG &#194;quackH &#194;quackI &#194;quackJ &#194;quackK &#194;quackL &#194;quackM &#194;quackN &#194;quackO &#194;quackP &#194;quackQ &#194;quackR &#194;quackS &#194;quackT &#194;quackU &#194;quackV &#194;quackW &#194;quackX &#194;quack &#194;quack &#194;quack= ciphertext

which turns the phrase 'this is fun' into 'rigq gq dsl'
LOL!
This really did turn out to be quite fun!

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