AKTU Cryptography and Network Security (BCS072) Question Bank with Solutions – B.Tech 4th Year Sem 7

This question bank has been compiled by UQuest (by University Academy) to help you prepare efficiently for the BCS072 Cryptography and Network Security semester examination (AKTU). Each of the five syllabus units contains 15 short-answer questions (2 marks) and 15 long-answer questions (7–10 marks), each with a complete, exam-ready solved answer including real, verified worked numericals (Caesar and Playfair cipher encryption/decryption, the Extended Euclidean Algorithm on gcd(1970,1066), Euler's Totient Function, a full RSA key-generation/encryption/decryption walkthrough, the Chinese Remainder Theorem, Fermat's Little Theorem, Miller-Rabin primality testing, the birthday-attack probability bound, and a full Diffie-Hellman key exchange with a man-in-the-middle illustration), and concept diagrams (security attack taxonomy, Feistel structure, DES structure, RSA flow, AES round structure, MAC/digital-signature flow, Diffie-Hellman exchange, Kerberos message flow, X.509/PKI hierarchy, IPSec AH/ESP modes, SSL/TLS handshake, and firewall/IDS placement) wherever applicable.

Understanding the Tags

• MOST IMPORTANT — Repeatedly asked across multiple AKTU examination years, or covers a core syllabus concept almost certain to be examined — prioritise these first.
• IMPORTANT — Asked in at least one recent AKTU examination, or a high-value supporting concept — cover these after the Most Important questions.

PYQ: AKTU <year> (<code>) — Indicates this question (or a very close variant of it) has actually appeared in an AKTU Cryptography and Network Security examination under BCS072 or a predecessor/parallel code (NIT-701 or KCS074) in the year shown, compiled from publicly archived AKTU question papers.

Suggested Preparation Strategy

• Start each unit with all questions marked ★ MOST IMPORTANT — these give the highest return on revision time.
• Work through every numerical (Caesar/Playfair ciphers, Extended Euclidean Algorithm, Euler's Totient, the full RSA example, CRT, Fermat's theorem, Miller-Rabin, the birthday-attack bound, Diffie-Hellman) by hand before checking the worked solution — AKTU consistently reuses the same style of numbers (e.g. gcd(1970,1066) has appeared in three separate years), and step-by-step working is heavily rewarded in AKTU answer sheets.
• Redraw every diagram (Feistel structure, DES structure, RSA flow, AES rounds, MAC/digital signature flow, Diffie-Hellman exchange, Kerberos flow, X.509/PKI hierarchy, IPSec modes, SSL handshake, firewall/IDS placement) from memory — diagram-based recall is heavily rewarded in AKTU answer sheets.
• Revise the ☆ IMPORTANT questions next, followed by the remaining questions for full syllabus coverage.
• Use the Detailed Syllabus section to confirm no topic has been missed before the exam.