CSEC 630 Lab Assignment 1 Introduction To Cryptography
Lab Assignment 1 - Introduction to Cryptography
Laurel Schneider
CSEC 630 - Prevention and Protection Strategies in Cybersecurity
University of Maryland University College
Jeffrey Daniels
February 21, 2015
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?
The Caesar cipher is a substitution cipher that substitutes one character for another and shifting the alphabet by a determined number of spaces. This type of cipher is vulnerable to statistical analysis. (Kendall, 2008). Therefore, a Histogram would be the most effective tool to use. The Histogram can be used to show “the relative frequency of each of the characters in the document”. (CSEC 630 Lab Assignment 1 – Introduction to Cryptography, n.d.). Since there are only 25 possible encryptions keys…”if we know how one letter should be deciphered, then we can determine the shift and decipher the entire message.” (Bryant & Ward, n.d.).
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?
Unlike the Caesar cipher, you do not see the high peaks and low valleys visually making it more difficult to identify the usage patterns. Because the Vigenère cipher is polyalphabetic and “works by adding a key repeatedly into the plaintext”(Anderson, 2008), frequency analysis is more difficult and is not as reliable. The Vigenère cipher can be broken using statistical techniques provided that “the ciphertext is long enough relative to the value of m”. (Goodrich & Tamassia, 2011)
Q3. There is an error in the following ciphertext representation of this quote, what is it? What should the correct ciphertext be?
Using the CryptTool and the Playfair encipher option, decoding the following ciphertext:
SDAHFOWGRABSSRERIVBYBSCIMQTFNIVETGHBSNQCNCSDTDHBSNQCD ECNICIFCTIC
Gave me this result:
THE DIFXFERENCE
Laurel Schneider
CSEC 630 - Prevention and Protection Strategies in Cybersecurity
University of Maryland University College
Jeffrey Daniels
February 21, 2015
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?
The Caesar cipher is a substitution cipher that substitutes one character for another and shifting the alphabet by a determined number of spaces. This type of cipher is vulnerable to statistical analysis. (Kendall, 2008). Therefore, a Histogram would be the most effective tool to use. The Histogram can be used to show “the relative frequency of each of the characters in the document”. (CSEC 630 Lab Assignment 1 – Introduction to Cryptography, n.d.). Since there are only 25 possible encryptions keys…”if we know how one letter should be deciphered, then we can determine the shift and decipher the entire message.” (Bryant & Ward, n.d.).
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?
Unlike the Caesar cipher, you do not see the high peaks and low valleys visually making it more difficult to identify the usage patterns. Because the Vigenère cipher is polyalphabetic and “works by adding a key repeatedly into the plaintext”(Anderson, 2008), frequency analysis is more difficult and is not as reliable. The Vigenère cipher can be broken using statistical techniques provided that “the ciphertext is long enough relative to the value of m”. (Goodrich & Tamassia, 2011)
Q3. There is an error in the following ciphertext representation of this quote, what is it? What should the correct ciphertext be?
Using the CryptTool and the Playfair encipher option, decoding the following ciphertext:
SDAHFOWGRABSSRERIVBYBSCIMQTFNIVETGHBSNQCNCSDTDHBSNQCD ECNICIFCTIC
Gave me this result:
THE DIFXFERENCE
References: Anderson, R. (2008). Security engineering: A guide to building dependable distributed systems. New York: Wiley. Bryant, L., & Ward, J. (n.d.). Caesar Ciphers: An Introduction to Cryptography. Retrieved February 21, 2015, from http://www.purdue.edu/discoverypark/gk12/downloads/Cryptography.pdf. CSEC 630 Lab Assignment 1 – Introduction to Cryptography. (n.d.). University of Maryland University College. Retrieved from https://learn.umuc.edu/d2l/le/content/57178/viewContent/2562147/View. Dent, A. W., & Mitchell, C. J. (2004). User 's Guide to Cryptography and Standards. Boston, MA: Artech House. Goodrich, M. T., & Tamassia, R. (2011). Introduction to computer security. Boston: Pearson. Kendall, J., Dr. (2008, June). Cryptographic Techniques for Network Security. University of Portsmouth. Retrieved from https://learn.umuc.edu/d2l/le/content/57178/viewContent/2562147/View. Rogaway, P. (2011). Evaluation of Some Blockcipher Modes of Operation. Cryptography Research and Evaluation Committees (CRYPTREC). Retrieved February 21, 2015, from http://web.cs.ucdavis.edu/~rogaway/papers/modes.pdf