Assume we store a one-time key on a CD-ROM with a capacity of 1 Gbyte. Discuss the real-life implications of a One-Time-Pad (OTP) system. Address issues such as life cycle of the key, storage of the key during the life cycle/after the life cycle, key distribution, generation of the key, etc.

Question two: Modern cryptography

DES

a) Explain the basic structure and working principle of the Data Encryption Standard.

b) What is the key size of DES, and why is it considered to be insecure by today\'s standards? c) Discuss the steps involved in the DES encryption process and the key expansion process. d) What is the role of the Initial Permutation (IP) and Final Permutation (FP) in DES?

AES

a) Describe the main characteristics and advantages of the Advanced Encryption Standard (AES).

b) Explain the different key sizes supported by AES and their impact on security.

c) Discuss the AES encryption process, including the Sub Bytes, Shift Rows, Mix Columns, and AddRoundKey steps.

d) How does AES achieve both confusion and diffusion in its encryption algorithm?

3DES (Tripple DES)

a) What is Triple Data Encryption Standard (3DES), and why was it introduced as an enhancement to DES?

b) Explain the different modes of operation that can be used with 3DES, such as ECB, CBC, and CTR.

c) Discuss the keying options available in 3DES and their impact on security.

d) What are the advantages and disadvantages of using 3DES compared to other symmetric encryption algorithms?