Codebusters Test Codebusters Cryptography Theory and History 5

Question 1

In Codebusters competition, the Aristocrat cipher is a monoalphabetic substitution cipher presented with:

Accepted Answer

Word boundaries preserved and no punctuation

Answer

No word breaks or punctuation

Answer

Numbers replacing letters

Answer

A hint keyword always provided

Question 2

A Patristocrat cipher differs from an Aristocrat in that a Patristocrat:

Accepted Answer

Removes all word divisions, presenting ciphertext as uniform 5-letter groups

Answer

Uses numbers instead of letters

Answer

Encrypts with two interleaved alphabets

Answer

Always includes a null character to mislead solvers

Question 3

Which digraph (two-letter combination) is the most frequent in standard English text and helps break substitution ciphers?

Accepted Answer

TH

Answer

QU

Answer

AE

Answer

OI

Question 4

The keyword 'ZEBRAS' in a Vigenère cipher means the first letter of the plaintext is shifted by how many positions?

Accepted Answer

25

Answer

26

Answer

1

Answer

0

Question 5

The Hill cipher uses which branch of mathematics as its foundation?

Accepted Answer

Linear algebra (matrix multiplication)

Answer

Calculus

Answer

Number theory (prime factorization)

Answer

Combinatorics

Question 6

What is a 'crib' in the context of WWII codebreaking at Bletchley Park?

Accepted Answer

A known or guessed piece of plaintext used to attack an encrypted message

Answer

A small notebook where codebreakers recorded guesses

Answer

A spare ENIGMA rotor kept for testing

Answer

A daily shift schedule for codebreakers

Question 7

In Codebusters, a 'running key cipher' differs from a Vigenère cipher because the running key:

Accepted Answer

Is taken from a long text source (like a book) so it does not repeat

Answer

Is a short repeating word

Answer

Uses numbers instead of letters as the key

Answer

Requires a 5×5 key square