Subject

Information security insurance

Need solution of all 3 questions ASAP

Q3. The following cipher text has been obtained used a simple Caesar Cipher. Decrypt it and write down the original plaintext. (3) OMJGDNKIVTCZASPRH FLEUYXWBVNPZ BIJDSROTQF KBUWJIPDNIMHK Q4. The following ciphertext is achieved by encrypting the plaintext with a row transposition cipher. The key used to encrypt the plaintext and the ciphertext is given here, your task is to recover the plaintext by performing decryption of the ciphertext. 6) Key = 3 1 5 6 2 4 7 Ciphertext UCTASAOOAIIRNOSARLTBOUMAUCIOFIVTNEOUOUECLTHTSL SNRSTOEIUP OISAFAIDFOTSSD Q5. In a public-key system using RSA, you intercept the ciphertext C = 20 sent to a user whose public key is e = 13.n=77. Calculate the plaintext M. (5) This question is about Hash functions which are used to check the integrity of a message. Hash functions take an input and produce a hash value of a fixed size for a certain algorithm. Following are few properties of good hash functions: 1. They take input of variable sizes and always produce the same and fixed size of output 2. The same message always produces the same hash value using the same algorithm. 3. They are resistant to collisions i.e. it is impossible to find two message ml and m2 such that H(ml) =H(m2). 4. These are one way functions, i.e. given a hash value, it is impossible to find the input message. 5. A small change in the input message reflects a major change in the hash value. A Hash function which does not satisfy any of the above characteristics is not considered a strong and good function and not recommended for use in situations where main goal is to get data integrity. In these questions, you will calculate hash values of different messages using different algorithms. You can use online Hash Calculator from this link. The files required for these two questions are zipped along with the midterm exam question folder you just downloaded from LMS. There are two files named shattered-1.pdf and shattered-2.pdf. Also create a new text file named message.txt which contains only lettera" inside it. Save this file on your Desktop. Now using the Online Hash Calculator, calculate the hash values of message.txt file and write the result in the following table *** Hash Algorithm Hash Value MD5 MD4 SHA1 SHA256 SHA384 SHA512 Now change the contents of message.txt and replace "a" with A which means that you are changing only 1 bit inside the contents of the message.txt file because "a" is represented by ASCII code 01100001 whereas "A" by 01000001. Calculate the hash value of this file again with new contents and fill the following table. Hash Algorithm Hash Value MD5 MD4 SHA1 SHA256 SHA384 SHA512