Information security — Winter 2025

Define substitution technique in cryptography. List various substitution technique and discuss any one with an example.

What is the objective of attacking an encryption system? Write the two approaches to attack a conventional encryption scheme.

List various modes of operations of block cipher. Explain any three of them briefly.

Define 1) Authentication 2) Data integrity 3) Data Confidentiality

Construct a Playfair matrix with the key “engineering”. And encrypt the message “test this process”.

Describe the Diffie-Hellman Key Exchange algorithm and how it enables secure key exchange between two parties. Explain the man-in-the-middle attack and how it can compromise the security of Diffie-Hellman.

Discuss RSA algorithm, focusing on its computational aspects and security. Discuss how public and private keys are generated and used in encryption and decryption.

What is the purpose of the State array? How many bytes in State are affected by ShiftRows?

Explain the following properties of hash function

One way property (ii) Weak collision resistance

Explain the structure of the Advanced Encryption Standard (AES), its transformation functions, and the key expansion process.

How does a Message Authentication Code (MAC) ensure message integrity and authenticity?

What is the difference between direct and arbitrated digital signature?

Briefly describe the main components of the Data Encryption Standard (DES) algorithm.1

Briefly define the monoalphabetic cipher.

Describe the Elgamal digital signature schemes.

Discuss Kerberos as a secure authentication protocol. Explain its key components and how it protects against replay attacks.

What are the essential ingredients of a symmetric cipher?

Describe the Schnorr digital signature schemes.

Explain the process of remote user authentication using symmetric encryption. How does it ensure secure communication between parties?

What is a nonce? What is the difference between a session key and a master key?

Discuss key expansion process of DES algorithm.

Discuss the Secure Hash Algorithm (SHA) family. Explain how SHA functions are used in ensuring data integrity and their role in cryptographic applications.

Explain the avalanche effect.

Briefly describe the role of X.509 certificates in secure communication.

What is public key cryptography? Explain the concept behind the public key cryptography and Compare it with conventional cryptography.