Introduction to Cryptography Using CrypTool - Coursework Example

? CrypTool Labs 2 (School) This particular report will include the responses to the questions regarding the first two labs that utilize the CrypTool software. Keywords: CrypTool, analysis, software, cryptography, labs Lab Part 1: Introduction to Cryptography Using CrypTool 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 text used for the purpose of this lab is the first few paragraphs of Douglas Adam’s Hitchhiker’s Guide to the Galaxy, along with additional text stating this is where the sample text was pulled from. The N-gram list of Caesar encryption of the document itself would be the most effective for a cryptanalyst to use to decipher a text encrypted with the Caesar cipher as it shows the frequency of each character used in the document. As E is the most commonly used letter of the alphabet, seeing that the highest frequency letter is H with 148 different instances of the letter would indicate that H is the substitute for the letter E. With this known, it can be seen that there is a shift of 3 present in this particular cipher. Once that has been determined, it would be a simple enough task to pair up all the other letters with their associated substitutions, and then translate the document back to its original text. Q2. What do you notice about the histogram results when text is encrypted with the Vigenere cipher in comparison to the results of the Caesar cipher? Why is this the case? The histogram results of the Vigenere cipher show an increase in the frequency of the letters that were used in the code word “applesauce” that encrypted the document. The Caesar cipher does not show this kind of across the board increase in particular letters due to the fact that it does not work off of an encryption key of this nature, but works instead off of an alphabet shift. Q3. There is an error in the following cipher text representation of this quote; what is it? What should the correct cipher text be? SDAHFOWGRABSSRERIVBYBSCIMQTFNIVETGHBSNQCNCSDTDHBSNQCD ECNICIFCTIC The error in the following cypher text occurs in the fourth to last letter of the text. The second to last C that is listed in the above cipher text should be an O instead. The cipher text for the quote, “The difference between stupidity and genius is that genius has its limits” should read: SD AH FO WG RA BS SR ER IV BY BS CI MQ TF NI VE TG HB SN QC NC SD TD HB SN QC DE CN IC IF OT IC. Q4. Of the three ciphers discussed (Caesar, Vigenere, Playfair), what are their relative degrees of security and why? Of the three ciphers discussed, the Caesar is the easiest cipher to break. This particular cipher may be found and used by anyone of any age; I can remember using it back in elementary school in order to pass notes in class. The Vigenere cipher is a bit stronger, requiring a more complex method of analysis in order to determine the proper code needed in order to unlock the “secret message.” It is the Playfair cipher, however, which shows itself to be the most secure of the three ciphers, as it removes all spacing, or generates its own spacing after every second character, making it impossible to guess the word without the need to “crack the code” first. Lab 2: Advanced Cryptography Functions Q5. For each of the following, state 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 For an online bank statement it would be most appropriate to use the CBC method of encryption, as this is the more secure of the two methods; the block chaining that is done in order to encrypt the document makes sure that this private information does not get into the wrong hands, while the ECB may show repetitive blocks, allowing for patterns to be shown and ultimately leading to the bank information being deciphered. An encrypted VoIP session would utilize the ECB method of encryption, as this would be the second layer of encryption, and as such, should there be any repetitive blocks, the person attempting to decipher the information would not end up with the information, but end up with the originally encrypted session, which utilizes a different form of cipher completely. For the viewing of a website using TCP/IP, it would be most appropriate to use ECB, for while the data itself may have a higher likelihood of being deciphered, the sites that contain personal information are already secured, and the only person or entity who may care about another’s browsing history would be a corporation interested in data mining for product information. The large majority of the populace will not care that a person visited 342 separate pages on http://lolcats.com. 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 encrypting a message with the values of p = 49, q=71, and e=13, the numbers input in base ten format are in blocks of three, and the cipher text encryption is broken into blocks of four. When using the values of p=673, q=619 and e=13, the numbers input in base ten format are in blocks of five, and the cipher text encryption is broken into blocks of six. Due to the way RSA keys are generated, and the myriad different keys that can be created, it would be difficult, but not impossible for these ciphers to be susceptible to statistical analysis. There are only a certain amount of prime numbers, and it would be possible, though not likely, for a person to use that information to be able to ascertain certain statistical data from the generated ciphers. Q7. Analyze the data encrypted with the RSA cipher. How does this encryption method compare to the other methods the Lab has covered? The RSA cipher generates text that looks similar to the output provided by the DES (CBC) cipher that was covered earlier in the lab. The text output of the encrypted file, while with different output, it is the same type and style of output that is presented for both of the ciphers. These two provide the closest comparative output to each other, with DES (EBC) following at a semi close third. The other ciphers that have been addressed throughout the course of this lab do not offer output that looks remotely close to the output provided by those three, or even by those initial first two, ciphers. 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 Hybrid RSA-AES cipher is the most secure of the ciphers that have been discussed throughout the course of this lab. It utilizes a separately generated RSA key in conjunction with the advanced encryption standard, which is specifically designed for the encryption of electronic data. By using two completely different types of cipher and combining them into one, there is a highly decreased likelihood of decrypting the data without the proper key. The combination of these two methods serves to provide the most secure method of encrypting data discussed so far. Read More