JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA 2017 INFORMATION SECURITY Previous Question Paper (August - 2017 - R15)

Computer security is essential to protect data confidentiality, integrity, and availability against unauthorized access or modification. It ensures business continuity and prevents financial or reputational loss. Attacks are generally categorized as passive attacks, where the attacker monitors transmissions without altering them (e.g., traffic analysis, release of message contents), and active attacks, which involve modification of data or creation of false streams (e.g., masquerade, replay, modification of messages, and denial of service).

The primary weakness of the Data Encryption Standard (DES) is its small key size of 56 bits, which makes it vulnerable to brute-force attacks. Modern computing power allows for exhaustive key searches in a relatively short time. Additionally, DES is susceptible to differential and linear cryptanalysis, which can break the algorithm with fewer operations than a full brute-force search. Its block size of 64 bits is also considered small by modern standards, increasing the risk of birthday attacks in certain modes of operation.