Lab Assignment #1:
Introduction to Encryption Algorithms

CSEC 630
University of Maryland University College
Professor Jingyu Zhang

1. Which tool or technique would be most effective for a cryptanalyst to use to decipher a text encrypted with the Caesar cipher, and why?
The best analysis tool to break the Caesar cipher is histogram because it performs a statistical analysis on cipher text which shows the frequency of each letter used in the file. This can later be compared and matched to the frequency of letters in the English language.
2. 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?
Histogram simply gives the frequency of each individual letter in cipher text without taking the plaintext into consideration. Since in Caesar cipher the relationship between plaintext and cipher text is one to one, histogram is more efficient to break the cipher. Since the key in vigenere is somewhat random the histogram shown below seems random as well.
3. There is an error in the following cipher text representation of this quote, what is it?
The original unencrypted message is:
TH ED IF FE RE NC EB ET WE EN ST UP ID IT YA ND GE NI US IS TH AT GE NI US HA SI TS LI MI TS
The original encrypted message is: THE CORRECT CIPHERTEXT
SD AH FO HL AR ST RE AS YL BS CI MQ TF NI VE TG HB SN QC NC SD TD HB SN QC DE CN IC IF OT IC
This is the error example:
SDAHFOWGRABSSRERIVBYBSCIMQTFNIVETGHBSNQCNCSDTDHBSNQCDECNICIFCTIC
This is the decrypted quote of the error example:
TH ED IF XF ER EN CE BE TW EX EN ST UP ID IT YA ND GE NI US IS TH AT GE NI US HA SI TS LI SC TS
I can see that the difference is that there are 2 letters inserted into the wrong one. There is an additional letter put in position 7 and 20. In the encrypted one it is displayed as an