Data Representation

Question 1

Describe how a 12-bit unisnged binary integer can be converted directly into hexadecimal e.g. 010010101110

Answer 1

• Put the bits into groups of 4 (starting at the right)
• Convert each of bits into a hexidecimal digit

Question 2

Why is hexadecimal used in preference to binary?

Answer 2

• Easier for people to understand / remember / read
• More compact when displayed
• Saves the programmer time when typing in data

Question 3

What are the disadvantages of the Caeser cipher?

Answer 3

• Each plaintext letter is always converted to the same ciphertext letter 🉐
• Frequency analysis of letters in ciphertext can easily reveal which plaintext letters they correspond to 🔍
• There are only 25/26 possible mapps from plaintext to ciphertext (brute forces can be used to find all possible mappings) ⌨️

Question 4

Why Vernam cipher is very secure?

Answer 4

• Ciphertext contains no useful information about plaintext 🤷
• Mapping from plaintext to cipher text is different for each letter position in the plaintext/ciphertext 🗺️
• Frequency analysis not possible, different plaintext letters can map onto the same ciphertext letter.