Breaking Ciphers

Breaking a cipher, also known as CRYPTANALYSIS, without having the key is quite difficult and very time consuming. And, depending on the type of cipher system used to create the secret message, there may be more than one key that cracks the code!


To break a message, it helps to know something about the message.


>> Who sent the message?    >> What language is the message written in?
>> Who was it sent to?         >> Is there a key word you can look for?


After answering these questions, try counting the number of times each letter is used in the message - this is called a FREQUENCY COUNT. Knowing how often letters are used can help you guess which cipher letter equals which plaintext letter. From there you can make other guesses based on language rules.


Today, high level encryption is done with complex mathematics and computers, and the same is needed to break them.

Helpful Hints About the English Language

Rather than trying to break the cipher randomly with different decryption methods, try using these English factoids the next time you try to break a secret message!

Letters

* The MOST COMMON letters used in the English language are E, T, N, O, R, I, A, & S.
* More than HALF of all English words end in E, T, D, & S.
* T is the most common FIRST letter of a word.
* E is the most common LAST letter of a word.
* Q is always followed by a "U."
* There are NO English words that end in "Q" or "J."

Words

* If a letter stands alone in a sentence, it can easily be identified as an "A" or an "I."
* The MOST COMMON word used in the English language is the word "THE."
* The word "STOP" replaces "." at the end of a sentence.

For example:
MEET AT SIX STOP BRING CANDY STOP

Doublets

* The MOST COMMON Doublets (when the same letter is used twice in a row) found in the English language are:


EE, TT, OO, SS, LL, FF
Examples include:
EERY ATTIC ROOM STOP ACCESS STILL CUTOFF STOP

2-Letter Combos

* The MOST COMMON 2-Letter combinations found in the English language are:
HE, RE, AN, TH, ER, IN
Examples include:
HELP STOP RESEND MAN WITH WATER INSIDE STOP

3-Letter Combos

* The MOST COMMON 3-Letter combinations found in the English language are:
ION, AND, ING, THE, ENT
Examples include:
UNION DISBANDING STOP TIMING THE DESCENT STOP