- What is meant by cryptanalysis?
- What are the two main ways in which a cryptosystem can be attacked?
- What is the main difference between a block cipher and a stream cipher?
- When we say an encryption algorithm is strong, what exactly do we mean?
- If a symmetric encryption key is 64 bits in length, what are the chances of an attacker guessing the right key on each attempt?
- What is the difference between a ciphertext only attack and a known plaintext attack? What is a chosen plaintext attack?
- It is impossible to design an unbreakable encryption scheme. Discuss this statement.
- What is meant by steganography? Give an example. What are its benefits and drawbacks, compared with encryption?
- What is meant by steganography? Give an example. What are its benefits and drawbacks, compared with encryption?
- Give an example of an encryption scheme that cannot be broken by brute force, no matter how much processing power is used
- Decrypt the following English text, which was encrypted with a Caesar cipher: VBPPHWULF
- What is a transposition cipher? Give an example.
- Describe the operation of a single round of a Feistel cipher.
- Give 3 examples of Feistel ciphers
- List the 5 elements that define a Feistel Cipher
- A Feistel cipher is described as follows: Block size: 8 bits No. of rounds: 4 Key size: 6 bits Round Function, F: XOR the two inputs and then perform a right circular shift of 1 bit on the result Subkey generation function: If we write the 6 bits of the key as b1 b2 b3 b4 b5 b6 then K1 = b1 b2 b3 b4 K2 = b3 b4 b5 b6 K3 = b2 b3 b4 b5 K4 = b1 b2 b5 b6 Using this cipher, encrypt the plaintext 01011100 with the key 110101.
- The Advanced Encryption Standard (AES) was selected in 2001 from several algorithms that met the minimum requirements laid down. List 5 of the criteria that were used to select from these qualified algorithms?
- Give an overview of the operation of the DES algorithm.
- Give an overview of the operation of the AES algorithm.
- Explain what is Triple DES (3DES) and how it differs from DES. Use a diagram.
- What are the drawbacks of using a block cipher in Electronic Codebook (ECB) mode?
- How does CBC (Cipher Block Chaining) work? Use a diagram to illustrate.
- Explain how a Counter Mode (CTR) cipher works. What are its advantages over chaining modes such as CBC.
- Explain how Cipher Feedback (CFB) mode allows a block cipher can be used as a stream cipher.
- How does link encryption differ from end-to-end encryption?
- Give one scenario where you might recommend link encryption over end-to-end encryption
- Give one scenario where you might recommend end-to-end encryption over link encryption