MCA-221
Applied Cryptography
Cryptography as it is actually deployed — classical ciphers, DES and AES, RSA and hashing, PKI and signatures, then TLS, Kerberos and OAuth.
- Semester
- Semester 3
- Credits
- 3
- Scheme
- 3 lectures a week
- Contact hours
- 42 across four units
- Category
- Core Elective - II
What the paper is
Applied Cryptography is the elective that turns the number theory from Discrete Structures into working security. It moves in the historical order — substitution and transposition, then symmetric block ciphers, then public key — and each step exists because the previous one was broken.
The emphasis is on application rather than proof. You are not asked to prove RSA secure; you are asked to encrypt with it, to choose a mode of operation, to explain why ECB leaks structure and CBC does not, and to say what a digital certificate actually asserts.
Unit IV is the deployed half — TLS, Wi-Fi security, sensor and RFID constraints, two-factor authentication, one-time passwords, Kerberos, SAML, OAuth, PGP and S/MIME — and it is the unit whose material you will meet again in any real system.
What to concentrate on
- RSA is the most examined single topic: key generation, encryption and decryption on small primes, worked by hand. Practise until the modular arithmetic is fluent, then do the same for a Diffie-Hellman exchange.
- Know the block cipher modes — ECB, CBC, counter — with a diagram each and one sentence on what each is good and bad at. The ECB-versus-CBC comparison is close to guaranteed.
- The classical ciphers in Unit I (Caesar, affine, Playfair, Hill, transposition) are quick numerical marks. Hill in particular needs matrix inversion mod 26; do it once before the exam rather than during it.
Syllabus, unit by unit
Summarised from the approved scheme. Hours are the contact hours the scheme allots, which is a fair guide to where the marks sit.
Unit I · Introduction and classical ciphers
10 hours- Introduction to cryptography, block ciphers and stream ciphers, types of attack
- The concept of modular arithmetic
- Substitution ciphers: Caesar, additive and multiplicative, affine, Playfair, Hill
- Traditional transposition ciphers
Unit II · Modern cryptography
12 hours- Symmetric cryptosystems: confusion and diffusion, DES and AES
- Encryption modes and their analysis: ECB, CBC and counter mode
- Public key cryptography and the RSA cryptosystem
- Hash functions and message digests
Unit III · PKI and digital signatures
10 hours- Introduction to the public key infrastructure
- Digital signature generation and verification methods
- Key management and distribution
- Digital certificates and the security of certification authorities
Unit IV · Protocols for secure communication
10 hours- Secure communication protocols: SSL and TLS; wireless security and Wi-Fi
- Secure protocols in resource-constrained environments: sensor networks and RFID systems
- Protocols for anonymous communication; two-factor authentication and one-time passwords
- Practical authentication and authorisation protocols: Kerberos, SAML and OAuth
- Secure mail: PGP and S/MIME
How it is examined
- Question 1 is compulsory, covers the whole syllabus, and is made of objective or short-answer questions. It carries 12 marks.
- The rest of the paper is four units matching the four above. Each unit sets two questions and you attempt one, so there are four more answers at 12 marks each.
- Examiners are asked to map every question to a course outcome using Bloom's taxonomy, which is why questions are phrased as “apply”, “analyse” or “evaluate” rather than only “explain”.
The pass mark is 40 out of 100 in every paper.
Learning objectives
- Fundamental knowledge of cryptographic technologies
- The security properties of cryptographic techniques
- Classical and modern cryptographic techniques
- How secure systems are engineered
Assumed beforehand
- Fundamental knowledge of number theory and modular arithmetic
Paired in the scheme with MCA-265 Lab based on Core Elective II.
Books it is taught from
- TB1William Stallings, “Cryptography and Network Security: Principles and Practice”, Prentice Hall, 6th edition, 2013
- TB2Atul Kahate, “Cryptography and Network Security”, McGraw Hill Education, 4th edition, 2019
Notes for MCA-221
Lecture notes, question papers and assignments filed against MCA-221 are in the library. Everything there has been checked by a moderator before it appears, and an account is free — new ones are approved by hand, which is what keeps the shelf clean.