Let’s be honest: Cryptography is usually the point in a Computer Science degree where the math gets “real.” One day you’re talking about simple passwords, and the next you’re drowning in modular arithmetic, prime number factorization, and the terrifying realization that your entire digital life rests on a few very complex equations.
Below is the exam paper download link
Past Paper On Fundamentals Of Cryptograpy For Revision
Above is the exam paper download link
If you’ve been staring at the Diffie-Hellman key exchange algorithm until your eyes cross, take a breath. Cryptography isn’t just about being a math genius; it’s about understanding the logic of trust. To help you stop guessing and start calculating, we’ve put together a “Plain English” guide to the toughest exam topics.
Below, you’ll find the answers to the questions that keep students up at night, followed by a link to download a full Fundamentals of Cryptography past paper for your own practice.
Your Crypto Revision: The Questions You’ll Actually Face
Q: Why do we use “Salting” with Hashing? Isn’t a hash supposed to be secure on its own?
A hash is a one-way street, but hackers have maps called “Rainbow Tables”—pre-computed lists of millions of common passwords and their hashes. If you use a simple hash, they just look it up. Salting adds a random string of data to the password before it’s hashed. This makes every hash unique, even for the same password, rendering Rainbow Tables useless.
Q: What is the “Man-in-the-Middle” (MitM) attack in the context of Key Exchange?
This is a favorite exam scenario. Imagine Alice and Bob are trying to agree on a secret key. Eve sits in the middle, pretends to be Bob to Alice, and pretends to be Alice to Bob. They both think they’ve established a secure line with each other, but they’re actually both talking to Eve. To stop this, we use Digital Certificates and Public Key Infrastructure (PKI).
Q: What is the difference between a “Stream Cipher” and a “Block Cipher”?
Think of a Stream Cipher (like RC4) as a steady flow of water; it encrypts data one bit or byte at a time. It’s incredibly fast and great for things like streaming video. A Block Cipher (like AES) is like a brick wall; it breaks the data into fixed-size chunks (blocks) and encrypts the whole chunk at once. Block ciphers are generally more robust but require more processing power.
Q: Why is RSA encryption so slow compared to AES?
RSA relies on the mathematical difficulty of factoring enormous prime numbers. Because the math is so heavy ($C = M^e \pmod{n}$), it takes a lot of CPU power. This is why we usually use RSA just to securely share a “session key,” and then switch to AES for the actual data transfer. It’s the best of both worlds: RSA for the “handshake,” AES for the “conversation.”
The Battle Plan: How to Use the Past Paper
Don’t just read the questions and nod along. If you want to ace this, you need to simulate the “pressure cooker” of the exam room:
-
Do the Math by Hand: Many papers ask you to perform a small-scale RSA calculation or a Caesar cipher shift. Use a pen and paper. If you can’t do it with small numbers (like $p=3, q=11$), you won’t be able to explain the theory behind the big ones.
-
Identify the “Attacker’s Goal”: When you see a question about a specific vulnerability, ask yourself: Is the attacker trying to read the message (Confidentiality), change the message (Integrity), or pretend to be someone else (Authentication)?
-
The “Birthday Paradox”: Make sure you understand why hash collisions are more likely than people think. If an exam asks about “Collision Resistance,” the Birthday Attack is almost always the intended answer.
Ready to Crack the Code?
Theory is the foundation, but practice is the house. To truly understand how ciphers are built and broken, you need to see the logic in action. We’ve compiled a comprehensive past paper that covers everything from classical substitution ciphers to modern elliptical curve cryptography.
