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Non-Technical Articles on Cryptography

Earlier Forms of Cryptography (Non-Technical)


(Notes: Continuing the series of articles on cryptography, here I will discuss the two early cryptographic techniques to better prepare readers for succeeding topics where I plan to cover symmetric key cryptography that will run up to the Russian One-Time Pads and the German Enigma which are the highlights of the second world war.)

Spartan SCYTALE. A device used for
early transposition cipher.

Previous: Introduction to Cryptography (Non-Technical)

Earlier Forms of Cryptography

Cryptography is a science and art that is continuously refined by one civilization after another. Some says it dates back to the Egyptians heiroglyphics which are intentionally cryptic to give it importance. Other says that it began with the ancient Chinese whose language have hidden meanings in their words.

Before I continue my discussion, we have to first know what a “cipher” is. Basically, a “cipher text” is what we call the gibberish stuff we see when a message is encoded. And ciphers are methods or set of steps that are followed during encryption and decryption.

In 5BC spartans developed a device that they used to send and receive secret messages called SCYTALE. It is probably one of the earliest “transposition ciphers”. Transposition ciphers, are types of ciphers where the letters of the plain text are jumbled or rearranged or “transposed”.

For example, if I want to say

I A M S E N D I N G A M E S S A G E (I am sending a message.)

I can say

I D E A I S M N S S G A E A G N M E

Where my cipher looks something like this:

I A M S E N

D I N G A M

E S S A G E

The principle of the SCYTALE is something similar.

[The] device, a cylinder called a SCYTALE, was in the possession of both the sender and the recipient of the message. To prepare the message, a narrow strip of parchment or leather, much like a modern-day paper streamer, was wound around the SCYTALE and the message was written across it. Once unwound, for transport to the receiver, the tape displayed only a sequence of meaningless letters until it was re-wound onto a SCYTALE of exactly the same diameter.

The transposition is one kind of cipher that became the basis of some modern day ciphers. [Read further on SCYTALE]

What is probably the most instinctive of all cipher is the substitution cipher and you don’t need a degree in mathematics or computing to do this. Remember when you were a kid and you (and your friends) used to have this “secret alphabet” so that your parents (and other people) wouldn’t know how to read it? That is what we call a substitution cipher where each element or letter is substituted to make the message incomprehensible to those who do not have the “key”. Well, this kind of cipher is the easiest to break due to the fact that there are certain letter whose probability of appearing is high depending on the language. In the English language, in particular, the letters E, T, A, O, N and S (ranked accordingly) have the highest probability of appearing in a message. So by applying our statistics, math and logic, we can easily break these kinds of ciphers. However, our parents doesn’t have a degree on math and computing either (and they don’t have the time to bother with math and statistics) so your secret as a kid are pretty safe.

One more example of the substitution cipher is the famous Caesar cipher (or Caesar’s cipher or Caesar shift). In this kind of cipher, the letter in the plain text is “substituted” by some fixed number of positions down the alphabet. Take for example, this picture, the key is B3 which means that the letter B would become E in the cipher text.

For example, if I want to say

I A M S E N D I N G A M E S S A G E (I am sending a message.)

I can say

 L D P V H Q G L Q J D P H V V D J H

Caesar recoded the use of this scheme and have been known to have used more complicated ciphers. There are evidence supporting that there had been more complicated substitution ciphers even before the time of Caesar. And this day, we cannot know how effective this cipher had been in the time of Caesar. [Read further on Caesar cipher]

Now that you have a basic knowledge of the substitution and the transposition cipher, it will be useful when studying more complex ciphers but before we move on to more complex ciphers which are basically the combination of the two, I will first introduce you to the concept of “symmetric ciphers”.

Basically, the idea with symmetric ciphers is that you have the code, and you have a key to unlock that code. In this type of cryptography, both the sender and the receiver shares the key.  In the case of the Caesar cipher example mentioned above, the key is B3 (or shift 3). Taking again the analogy of the house that I used in the previous article, the sender and the receiver are holding identical copies of keys for the front door. Now this can provide a relatively good security if the key is guaranteed to remain secret. Or in the case of the house analogy, if the key will remain solely in the hands of the sender and the receiver.

Symmetric Key Cryptography paved the way to two of the world’s strongest and most unforgettable encryptions: the German Enigma and the Russian One-Time Pads. They played a very important role on the second world war, and understanding them will help us better understand the importance of information and its security in our times. Understanding the role they played will provide us the insight necessary in understanding the arm race between cryptographer and cryptanalysts as well as the different cryptographic techniques that generations after generations have tried to shape and reshape inventing and re-inventing the cryptography and information security that we know today.

Terms covered in this article:
Cipher, Transposition cipher, Substitution Cipher, Symmetric Cipher/Symmetric Key Cryptography

Sources and Further Readings
Cypher Research Laboratories. A Brief History of Cryptography [pdf] [web]
Wikipedia. History of Cryptography [web]
Fred Cohen. A Short History of Cryptography [web]
images are courtesy of Wikipedia.

Next: Symmetric Key Cryptography (Non-Technical)

(Notes: For practical and obvious reasons, I cannot keep explaining cryptography, cryptanalysis, encryption, decryption, etc. in every article so it is advised to read the previous article before reading this one. Feedbacks, corrections and suggestions will be appreciated. 🙂 )

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About princess of antiquity

Abbi Cabanding is a member of the Security Bloggers Network and had been blogging on information security since 2006. She is also a member of the Association for Computing Machinery. She studied Computer Science and Fine Arts at the University of the Philippines - Diliman.

Discussion

8 thoughts on “Earlier Forms of Cryptography (Non-Technical)

  1. This is a well written article! I look forward to the next installment of this series; I’ve long found an interest in the use of crypto back in the late 30’s and into 40’s during WWII…which just reminded me of a silly GeoCache I hid several years ago with a non-historically correct WWII crypto theme (http://tinyurl.com/5aok4d) 😉

    Posted by Steve Zenone | June 24, 4:43 am, 4:43 am
  2. what is your name?
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    thankyou 😀

    Posted by asjhgblsg | November 9, 6:01 pm, 6:01 pm
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    Posted by Michael Tim | March 1, 1:02 am, 1:02 am
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    Posted by Ted Burrett | April 22, 2:39 pm, 2:39 pm
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Trackbacks/Pingbacks

  1. Pingback: Interesting Information Security Bits for June 24th, 2008 « Infosec Ramblings - June 25, 2:24 am

  2. Pingback: Symmetric Key Cryptography (Non-Technical) « Princess of Antiquity - April 30, 6:39 pm

  3. Pingback: Introduction to Cryptography (Non-Technical) « Princess of Antiquity - April 30, 6:50 pm

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