NNAT3 Pattern Recognition 1 — Questions and Answers
Question 1: What is a Caesar cipher?
- A substitution cipher that shifts each letter by a fixed number of positions (Correct answer)
- A modern encryption algorithm
- A random letter replacement
- A mathematical hash
Correct answer: A substitution cipher that shifts each letter by a fixed number of positions
The Caesar cipher shifts each letter in the plaintext by a fixed number of positions in the alphabet. For example, with a shift of 3, A becomes D.
Question 2: What is frequency analysis used for in cryptography?
- To break substitution ciphers by analyzing letter frequency patterns (Correct answer)
- To count words in a document
- To measure radio frequencies
- To analyze sound waves
Correct answer: To break substitution ciphers by analyzing letter frequency patterns
Frequency analysis exploits the fact that certain letters (like E, T, A in English) appear more often, allowing codebreakers to identify substitution patterns.
Question 3: What is the difference between a cipher and a code?
- A cipher transforms individual characters; a code replaces entire words or phrases (Correct answer)
- They are the same thing
- A code is more secure
- A cipher is older
Correct answer: A cipher transforms individual characters; a code replaces entire words or phrases
Ciphers operate on individual characters (letter by letter substitution or transposition), while codes replace entire words or phrases with other words or symbols.
Question 4: What is a transposition cipher?
- A cipher that rearranges the order of letters without changing them (Correct answer)
- A cipher that replaces letters with other letters
- A modern computer encryption
- A hash function
Correct answer: A cipher that rearranges the order of letters without changing them
Transposition ciphers keep the original letters but rearrange their positions. Examples include rail fence and columnar transposition ciphers.
Question 5: What is a one-time pad?
- A theoretically unbreakable cipher using a random key as long as the message (Correct answer)
- A single-use notebook
- A disposable computer
- A temporary password
Correct answer: A theoretically unbreakable cipher using a random key as long as the message
The one-time pad uses a truly random key at least as long as the message, XORed with the plaintext. When used correctly, it is mathematically proven to be unbreakable.
Question 6: What is the Enigma machine?
- A WWII German cipher machine using rotors for polyalphabetic encryption (Correct answer)
- A modern computer
- A code-breaking device
- A telegraph machine
Correct answer: A WWII German cipher machine using rotors for polyalphabetic encryption
The Enigma machine used a series of rotating wheels (rotors) to create complex polyalphabetic substitution ciphers, famously broken by Allied codebreakers.
NNAT3 Pattern Recognition 1
What is a Caesar cipher?