Carrying messages across enemy lines, setting up midnight rendezvous, or secret attacks all have been strengthened by using secret codes. Ciphers and codes have been used since ancient times in many different shapes and forms to protect messages from being intercepted. Ciphers and codes have even crept into many popular mediums from Harry Potter books to the hit movie and book, The Da Vinci Code. (1).
Today, we still see ciphers in the form of encryption. Encryption is the ability to render a message unreadable without special knowledge to decrypt it. It's everywhere, from encrypted government secrets to emails sent around the office; the use of encryption has become a part of everyday life.
Ciphers and Codes
Though ciphers and codes are often thought to be the same they are, in fact, two separate methods for disguising communication data.
Codes provide exchanges for pictures, words, or numbers for words or phrases and will only have a set amount of words or phrases that can be decoded.
Ciphers exchange individual letters for other letters or numbers breaking down messages to a far greater degree (1). a
Ciphers also have the advantage of being able to be shifted very quickly since instead of having a set number of phrases or words in a code it uses an algorithm to define any possible word or phrase.
Through the complex and systematic nature of ciphers, which are used over codes for encryption. By looking at the history of ciphers we can get a better understanding of how and why encryption works in today's world.
Atbash - A Basic Cipher
Early religion provided us with some of the most basic ciphers we know about. Judaism brought forth the Atbash. Atbash is a "substitution cipher", which means that every letter is exchanged for another in the alphabet. In this case, it's the first letter of the alphabet for the last. While this is very basic, most people couldn't read let alone break codes at 600BC.
When in Rome, Keep Secrets: The Caesar Shift
Ancient Rome and famed emperor Julius Caesar carried ciphers to new level. Caesar used a cipher as a means to carry commands to his generals and allies. Using what would be later dubbed "Caesar shift", he made his messages unreadable to those who didn't have the shift sequence.
Another form of substitution cipher the method was to simply shift the letter wanted by three later for example, A > D, B >E and C >F. If a message said "spy" would look like this in the Caesar Shift:
S > V, P >S and Y >B. vsb
The phrase "ad astra," shoot for the stars would translate to "DG DVWUD" in the Caesar Shift
It was quickly adapted to be any variable amount of places in the shift.
Rot13 - A Cipher Novelty
ROT13 sounds like something Hermione Granger uses on her O.W.L.s.(2) , but is a variation of the Caesar Shift, it uses a 13 letter/character replacement sequence. Rot13 is still used often today, though more as novelty than keeping any secrets.
Message boards that reveal the ending of a book or movie have used the Rot13 method to protect others from accidentally reading spoilers. Harry Potter fans, you may just find out what "he who must not be named" means to do to young Mr. Potter in book seven, the Deathly Hallows.
Modern Encryption
The advent of the computer revolutionized the world of codes. All of the ciphers above could be cracked with computer programs in a matter of seconds with the right software. Both the building and breaking of stronger ciphers have been blazing along as technology provides new tools that have forever changed cryptography. Modern uses of ciphers have led to advanced computer technology that is known as encryption.
One method of encryption is Public Key Encryption (PKE). The PKE cipher is radically stronger than those used in ancient times. Imagine two prime numbers (a number that can only be divided by one and itself) for example 17 and 13. When you multiply these two numbers you come up with 221, and is known as the modulus.
To an outsider, 221 would have no meaning since there are plenty of factors that could be broken down. There also needs to be a random number that has a value somewhere between 1 and the product of the two prime numbers. In a PKE cipher, a formula is made where the a variable will be sought out:
Prime#1 * Prime#2= A
Random# must be between 1 and A
Solution Must be a whole Number
(X * random# )-1 = (Prime#1-1) * (Prime#2-1)
X will be the private key used for the encryption and the two prime numbers will be the public key given out. As you can see, if PKE is Superman, Atbash is an amoeba.
To find each number's code you would take the value of a number (A=1 and... Z=26) and raise it to the power of the random number used earlier. After that each number is figured out using a system called "modular arithmetic" (3) .
If all this sounds confusing don't worry that's the point of cipher! The prime numbers used in software encryptions are hundreds of digits long. Making it dramatically more secure and difficult for someone to try and discover how the code can be broken. It would take the Bat computer, Professor Dumbledore and a legion of Scooby's to break a PKE cipher.
For encrypting computer files, the same process occurs where the file is broken up into sections of bits. The smaller the number of bits per section, the stronger the level of encryption will be. Instead of letters being converted it is 0 and 1 of binary.
Evolution of Encryption: Email Anti-Theft, Locking Down Your Email
Not only has the strength of encryption increased by leaps and bounds with computer speeds, but it has become used in everyday actions. Email Anti-Theft software can allow individuals who know nothing about encryption to apply heavy protection settings to outbound email files with the same ease as an unencrypted email. Email anti-theft technology allows a system where there's no manual key exchange, yet the outbound email files don't lose any encryption strength when sent outside your company.
Importance of Encryption
Computers aren't the expensive and slow behemoths they were in the 1970s, 1980s and 1990s. Today the even the most affordable PC is able to store countless files and run thousands of scenarios a minute. To protect private information the encryptions has to be strong enough to endure computerized attacks.
A weak cipher can have its algorithm discovered and deciphered quickly; where as strong encryption could withstand almost any length of deciphering assaults (4) . While you may not be sending commands to you armies in the east, your email messages, banking documents and other private bits of data still deserve the highest level of security.
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End Notes:
1) Also referred to as "cyphers," in British English, a secret method of writing, as by transposition or substitution of letters, specially formed symbols, or the like. Dictionary.com, 29 March, 2007. http://www.dictionary.com
2) Secrets have been a mainstay in the popular book series, Harry Potter. O.W.L. (Ordinary Wizarding Level) exams are the wizarding world's equivalent to the S.A.T.s
3) Pincock, Stephen. Codebreaker: The History of Codes and Ciphers, From The Ancient Pharaohs to Quantum Cryptography. New York: Holtzbrinck, 2006.
4) Ibid
