This assignment is designed to help you improve your critical thinking and problem solving skills, as well as your information literacy skills (i.e. the ability to select and organise information and to communicate it effectively and ethically).
1.What can organizations do to fight back against typo squatting? Research the Internet to find out how companies are combating this growing problem. How can these typo squatting sites be taken down? What must a company do in order to stop these sites? And why has it been so difficult to do this? What proactive steps can a company take? Write a short report on your research.
2.Attacks that exploit previously unknown vulnerabilities are considered some of the most dangerous attacks. Use the Internet to research these attacks. How are the vulnerabilities discovered? What are some of the most recent zero-day attacks? What defenses are there against them? Write a short report on your research.
3.How does Diffie-Hellman key exchange protocol works? Use the Internet to research this key-exchange protocol. Then visit the website http://www.dkerr.com/diffie hellman calc.html to see how values are created. Provide a numerical example and show how the ‘man-in-the-middle’ attack works in this protocol. write a short report on your research.
4.In this question you learn a classical polyalphabetic substitution cipher (known as Vigen´ere cipher), and are required to cryptanalysis a given cryptogram. Cryptanalysis of an information system is the study of mathematical techniques for attempting to defeat information security services. A cryptographic system is said to be breakable if a third party (i.e., cryptanalyst), without prior knowledge of the key, can systematically recover plaintext from corresponding ciphertext within an appropriate time frame.
Julius Caesar used a cipher which moved each letter of the alphabet to the letter three to the left in the predetermined order of the letters of the alphabet. Figure 1 shows original English alphabet and corresponding cryptogram alphabet in Caesar cipher:
a b c d e f g h i j k l m n o p q r s t u v w x y z
d e f g h i j k l m n o p q r s t u v w x y z a b c
In order to use mathematical notations, let convert letters of the alphabet to integers. The most natural conversion is to assign to each letter an integer which indicates the position of the letter in the alphabet. That is, assign 0, 1, · · · , 24, 25 to a, b, · · · , y, z, respectively. Using this conversion, Caesar cipher can be expressed as:
where ‘C’ is the cryptogram, ‘E’ is the encryption algorithm, ‘k’ is the key, ‘M’ is the message/plaintext (one may replace integer 3 by letter ‘d’).
Caesar cipher is from the family of shift ciphers, in which the cryptogram is a shifted version of the original alphabet. Cryptanalysis of the Caesar (and all shift ciphers) is easy, because there are 26 possible keys/shif
In Vigen´ere cipher the key is more than one letter. That is, Vigen´ere cipher can be considered as a combination of n shift ciphers, where n is the key-length (i.e., the number of letters in the keyword). Let the message/plaintext be ‘individual character’ and the keyword is ‘host’. Vigen´ere cipher encrypts the message as follows:
Plaintext i n d i v i d u a l c h a r a c t e r
Keyword h o s t h o s t h o s t h o s t h o s
Cryptogram p b v b c w v n h z u a h f s v a s j
That is, the first four letters of cryptogram computed as:
‘i’ + ‘h’ = 8 + 7 = 15 (mod 26) i.e., p
‘n’ + ‘o’ = 13 + 14 = 1 (mod 26) i.e., b
‘d’ + ‘s’ = 3 + 18 = 21 (mod 26) i.e., v
‘i’ + ‘t’ = 8 + 19 = 1 (mod 26) i.e., b
Since the plaintext is longer than the keyword, keyword is repeated till all letters of the plaintext are encrypted. As it can be seen, a particular letter of the plaintext may be encrypted with different letters from the keyword. For example, the first occurrence of letter ‘i’ from the plaintext is encrypted with ‘h’, where its second and third occurrences are encrypted with letters‘t’, and ‘o’ respectively. That is, Vigen´ere cipher is a polyalphabetic substitution cipher.
To break a polyalphabetic substitution cipher, the cryptanalyst must first determine the period (i.e., the key-length) of the cipher. This can be done using two main tools: the Kassiski method, and the index of 2 coincidence. Here we explain Kassiski method, you may search the Internet for the index of coincidence method.
The Kassiski method uses repetitions in the ciphertext to give clues to the cryptanalyst about the period. For example, suppose the plaintext ‘to be or not to be’ has been enciphered using the key ‘now’, producing the ciphertext below:
Plaintext t o b e o r n o t t o b e
Keyword n o w n o w n o w n o w n
Cryptogram g c x r c n a c p g c x r
In the given cryptogram (i.e., g c x r c n a c p g c x r) contains the pattern g c x r which is repeated and the distance of repetition is 9. This could be the sign in which the same letters from plaintext is encrypted with the same letters from the keyword. Since in Vigen´ere cipher the keyword is repeated, the key-length is probably 9 or a divisor of 9 (i.e., 3, because 9 has no other divisor). Assuming that the key length is 3, we split the cryptogram into three cryptogram. That is, the 1st, 4th, 7th, ... characters of the cryptogram are the result of the shift of the 1st, 4th, 7th, ... characters of the plaintext where the shift is the first letter of the keyword. Similarly, the 2nd, 5th, 8th, ... letters build another list. That is, this Vigen´ere cipher is a combination of 3 Caesar cipher.
In the following you can find 10 cryptograms, that are created by Vigen´ere cipher, where the plaintext is English text and the keyword is meaningful English word. You are required to decipher the cryptogram that matches with your Student-ID.