Assignment on Cryptography & Network Security

 

Assignment-1 Questions

SET-1:

1. Briefly define the monoalphabetic cipher. What is the difference between a monoalphabetic cipher and a polyalphabetic cipher?
2. Explain the Play Fair cipher algorithm? Encrypt the message ‘MY BALLOON’ using the key ‘MONACHRY’
3. Discuss any four Substitution Technique and list their merits and demerits.
4. Explain the DES algorithm with neat sketch.
5. Explain about Hill Cipher. Consider the plaintext "paymoremoney" and use the encryption key: K=

Find the cipher text.

SET-2:

1. Define Steganography and Hash function.
2. Write notes on two basic functions used in encryption algorithms?  Also differentiate between public key and private key.
3. Identify the attacks on block ciphers.  Also define Group and Ring in block ciphers.
4. What do you mean by Substitute byte transformation in AES?  Which four tasks are performed in each round of AES Cipher?
5. How to use Chinese Remainder Theorem to reconstruct integers from their residues modulo functions.

SET-3:

1. Explain the followings: (a) Playfair cipher  (b) Vernam cipher
2. Explain the basic principle of rotor machine.
3. Explain in Detail about DES Algorithm
4. What are the design parameters of Feistel cipher network?
5. Write the difference between ECB and CBC with neat diagram

SET-4:

1. Explain the importance of cryptography in the evolution of secure communication with suitable historical examples.
2. Differentiate between substitution and transposition techniques in classical cryptography.  What is the main difference between a stream cipher and a block cipher?
3. What is steganography? How does it differ from cryptography? Explain.
4. Explain in detail about AES algorithm
5. Explain about Chinese Remainder theorem

SET-5:

1. Explain the working principle of the Caesar cipher. Encrypt the text "NETWORK" using a key value of 3.
2. Explain the work of a Rotor Machine with a simple example. Show how a single plaintext letter is transformed through multiple rotors into ciphertext.
3. Describe the working of a Columnar Transposition Cipher by encrypting the message “CRYPTOGRAPHY IS FUN” using the keyword “NETWORK.” Show column arrangement, transposition steps, and final ciphertext.
4. Explain the key expansion round key generation logic used in DES. How do round keys enhance security?
5. Explain the structure and working of the Advanced Encryption Standard (AES). Include key sizes, block size, and the role of Sub-Bytes, Shift-Rows, Mix-Columns, and Add-Round-Key operations.

SET-6:

1. Compare and Contrast stream ciphers and block ciphers.
2. Briefly explain the design principles of block cipher.
3. What is the block size used in the Advanced Encryption Standard (AES)?  Also state few applications of the Chinese Remainder Theorem (CRT) in cryptography.
4. Describe common attacks on block ciphers like brute-force, differential, linear cryptanalysis. Explain how block cipher design principles help resist these attacks.
5. Explain the Chinese Remainder Theorem (CRT) with a numerical example. Solve for x in the system: x ≡ 1 (mod 3), x ≡ 2 (mod 4), x ≡ 3 (mod 5).