Classic Cryptography: Making and Breaking Codes


In our previous entry on steganography, we mentioned its application of building secure communications between two individuals by concealing a message within another. We also mentioned cryptography, the practice of writing in a secret code, and another method of allowing two parties to communicate without having a third party intercept. 

 [Photo credit: The University of Manchester website]

Like steganography, cryptography has also been practiced widely throughout history, such as for protecting wartime strategies. Its modern use also includes keeping your own data secure from theft, such as when you make transactions or correspond with others over the Internet. For web sites to be secure, data transmitted between computers have to be encrypted

 [Photo credit: Comp Ed Online website]

Imagine making an online purchase with your credit card, only to find that your account information has been compromised, or sending an email to someone, only to find that another party has read it! This highlights the importance of keeping your data secure. 

In this entry, we'll introduce two simple historical methods of cryptography. 

The Atbash Cipher

This simple substitution cipher (also sometimes referred to as a mirror cipher) was originally used for the Hebrew alphabet, but can be adapted for the Latin alphabet. 

If our plaintext (original message) is: MEET ME TONIGHT

To encrypt this into our ciphertext (altered message), simply follow this key: 

[Photo credit: Geocaching website]

Substitute each letter in the plaintext with the corresponding letter on the other line. This will give you the following ciphertext: ZRRG ZR GBAVTUG.

Decrypting the message is equally simple: replace the ciphertext letters with their corresponding letters on the other line. Because it is very easy to solve and only has one key, this is considered to be a weak cipher. 

The Scytale Cipher

Considered as the oldest military cipher, the Spartans used this method to communicate during their campaigns. The scytale is a baton with a papyrus band or parchment wound around it. When given the papyrus, you would see a seemingly jumbled sequence of letters: the ciphertext. 

[Photo credit: Bekkah Walker's website]

The recipient would then wrap the parchment around a baton with the same diameter to read the message imprinted on it. Spartan general Lysander was said to have used the scytale in the 5th century BCE. This is an example of a transposition cipher, where the letters are rearranged or scrambled to form the ciphertext. 

 [Photo credit: Flylib website]

Want to learn more about cryptography and other intriguing espionage techniques? Join our CSI 101: Night at the Museum activity on September 26 (7PM - 12MN) for a fun night out with your friends! Complete mental and physical challenges, gather evidence, and solve the case! 


To register for the event, click on the following link: Registration Form
Also join our Facebook event page for updates at: Event page
The deadline for registration is on September 23, so sign up now!

REFERENCES: 

1. Kessler, G. C. (July 8, 2015). "An overview of cryptography". Retrieved from: http://www.garykessler.net/library/crypto.html
2. Kozdron, M. (2006). "Transparencies from June 27, 2006". Retrieved from Cornell University website.
3. Yashchenko, V. V. (2002). Cryptography: An introduction. USA: American Mathematical Society.
4. Sheldon, R. M. (2008). Espionage in the ancient world: An annotated bibliography of books and articles in Western    languages. USA: McFarland.

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