Cryptography is yet another domain of the CISSP exam which is exciting and fascinating. I have already written several posts on Cryptography on my blog(Caesar cipher)
To refresh, cryptography involves hiding the information to be transmitted so that only the receiver is able to view it. This is done by encoding the information to be sent at the sender’s end and decoding the information on the receiver’s end.
With so many blog articles written about the subject, our focus will be mostly on the Scytale cipher in this post.
The text that is to be transmitted which can be commonly read is known as ‘plaintext’. This plaintext is converted to unreadable format by the process of encryption and it is then known as ‘Ciphertext’. This ciphertext can now be transmitted over insecure channels confidently without the danger of snooping. Once it has been successfully transmitted, it has to be decrypted at the receiver’s end and the ‘plaintext’ is again recovered. An algorithm is a complex mathematical formula that aids in encrypting the information along with the “key”. The “key” is a long sequence of bits which is used to encrypt and decrypt text. This is the basic and fundamental concept behind cryptography. There are two modes of encryption – the symmetric algorithm and the asymmetric algorithm. In the symmetric cipher – both the sender and receiver use the same key. In asymmetric cipher – both the sender and receiver use a different key.
The Scytale cipher:
The Scytale cipher is a transposition cipher which is a type of symmetric cipher. A transposition cipher is one where the plaintext is shifted according to a certain pattern to encrypt it. To decrypt it, the shifting is reversed to obtain the original plaintext.
Now moving onto Scytale cipher – it is one of the most interesting of all the ciphers. It is again an ancient form of encrypting messages and it is said to have been used by Greeks and Spartans to send secret messages during military campaigns.
The basic idea behind the Scytale cipher is to wrap a long belt of characters (written on the wrong side) around a log or piece of wood of the correct diameter. Once that is done, the encoded message will be decoded. The key here is to obtain the log or piece of wood of the correct diameter. If the correct diameter is not obtained, the message will be gibberish.
Practical example of the Scytale cipher:
| Start | 1 | 2 |
| D | ||
| G | ||
| U | ||
| O | ||
| K | ||
| L | ||
| O | ||
| C | ||
| 1 | 2 | End |
For those very eager to try this cipher, consider this table given above. Cut the three strips of paper along the columns and tape them one below the other without any overlaps.
Once that is done, wrap the paper strips in order around an empty paper towel roll without any overlaps. This will reveal the message. What was the message? 🙂
The important point again is to make sure that an empty paper towel roll is used to decipher the message. Rolling it on any other medium of different diameter will result in gibberish message. (The Scytale Cipher)
Cryptography is a growing field with modern day’s requirements and many other ciphers like the substitution ciphers are a good read too.
Bibliography
Harris, S. All in one CISSP. In S. Harris.
The Scytale Cipher. (n.d.). Retrieved from http://library.thinkquest.org/04oct/00451/scytale.htm
Answer is this:
