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# Lab Assignment Essay

Q1. Which tool or technique from the above list would be most effective for a cryptanalyst to use to decipher a text encrypted with the Caesar cipher, and why?

Floating frequency is the most effective tool used to decipher a text encrypted with the Caesar cipher. Floating frequency replace one letter of the plaintext with another to produce the cypher text, and any particular letter in the plaintext will always, in the simplest and most easily breakable of these cyphers, turn into the same letter in the cypher. For instance, all E’s will turn into X’s. Floating frequency is based on the fact that certain letters, and combinations of letters, appear with characteristic frequency in essentially all texts in a particular language (Introduction To Codes, Ciphers, & Codebreaking, 2010).

Q2. What do you notice about the histogram results when text is encrypted with the Vigenère cipher in comparison to the results of the Caesar cipher? Why is this the case?

I’ve notice between the two ciphers the Caesar cipher was easier to see a pattern between the alphabets oppose to the Vigenere cipher which was much harder to see a pattern. The Caesar cipher would be much easier to crack because one would be able determine a pattern rather than the Vigenere cipher which would be much harder to break.

Q3. There is an error in the following ciphertext representation of this quote, what is it? What should the correct ciphertext be? (Hint: when using the CrypTool there are several ways to decode one that you can use is “Playfair” encipher option, the plaintext and key provided in the lab information, and DESELECTING the “separate duplicate letters only within pairs” option)

SDAHFOWGRABSSRERIVBYBSCIMQTFNIVETGHBSNQCNCSDTDHBSNQCD
ECNICIFCTIC

The error is the ciphertext included additional alphabets located below in Red: THE DIFXFERENCE BETWEXEN STUPIDITY AND GENIUS IS THAT GENIUS HAS ITS LIMITS

The correct ciphertext should be:
The difference between stupidity and genius is that genius has its limits.

Q4. Of the three ciphers discussed (Caesar, Vigenère, Playfair), what are their relative degree of security and why?

The Caesar cipher is less secured because it is very easy to the key. For the Caesar cipher there are 26 alphabet characters meaning there are 25 possible keys and the 26 key would be in plaintext. All someone have to do to crack the code is to try all alphabet shift until the coded message is revealed (Caesar Shift Cipher, 2011). The Vigenere cipher can be crack as well because the security of this cipher is directly related to the length and security of the keys. The code can be crack simply by guessing the key length (Vigenère Cipher, 2011). As far as Playfair goes it is more secured because then instead of the 26 alphabet characters the Caesar cipher uses, Playfair instead uses 600 possible characters to determine the code (Playfair Cipher, 2013).

Q5. For each of the following say whether ECB or CBC would be most appropriate and give a brief explanation as to why.
a. an online bank statement
b. an encrypted VoIP session
c. viewing of a website using TCP/IP

A. CBC would be used for an online bank statement because bank statements included a lot of personal information such as account numbers, bank transactions and account balances.

B. ECB would be used for an encrypted VoIP session because VoIP protocols are connectionless.
C. When viewing of a website using TCP/IP I would recommend CBC because TCP/IP delivers packets in order and TCP/IP is not connectionless which means it the delivering packets needs to be more secured.

Q6. What difference do you notice in the block size, discuss whether or not this cipher would be susceptible to statistical analysis and why.

When a smaller value is used for “p” and “q” the block size is smaller, however the number of blocks become much larger. When the “p” and “q” value is larger the block size increases, however the number of block are now much smaller. Since this cipher uses both numbers and characters to encrypt/decrypt it is not susceptible to statistical analysis.

Q7. Analyze the data encrypted with the RSA cipher. How does this encryption method compare to the other methods the Lab has covered?

RSA cipher is on the same level of security as Caesar and Vigenere meaning it is less secured then Playfair. Furthermore, smaller RSA key sizes are becoming obsolete due to their vulnerability to specific cracking algorithms because the use of higher performance computers. RSA uses both public key and private key. However the private key is not secured but if a larger value was inputted it would take a little longer to crack. As for the public key that too is less secured because if public key value is known, then the private key can be easily known.

Q8. What are the advantages of the Hybrid RSA-AES cipher? How does this encryption method compare to the other methods the Lab has covered?

The advantages of the Hybrid RSA-AES cipher is that any data with encryption and decryption the key is secured. RSA using a key size of 128-bytes. When both the public and private keys are generated. The public key will encrypt the data that is being sent to the recipient. When the recipient receives the data it will be decrypted using both public and private keys. This encryption is more secure than the other methods covered in the lab both the encrypt/decrypt data key is secured.

References:

Introduction To Codes, Ciphers, & Codebreaking. (2010, July 13). Retrieved from Vectorsite: Introduction To Codes, Ciphers, & Codebreaking