Codebusters Test Codebusters Pattern Recognition 5

Question 1

In a Vigenère cipher with keyword 'ACE', which shift is applied to the 4th plaintext letter?

Accepted Answer

0 (key letter A)

Answer

The keyword ACE cycles repeatedly; positions 1,4,7... use A (shift 0), positions 2,5,8... use C (shift 2), positions 3,6,9... use E (shift 4).

Question 2

A student notices ciphertext letter 'J' never appears in a 300-character Aristocrat message. What does this most likely mean?

Accepted Answer

Its corresponding plaintext letter simply never appeared in the original message

Answer

In monoalphabetic substitution, every plaintext letter has one fixed ciphertext equivalent; if a plaintext letter never occurs, neither does its ciphertext pair.

Question 3

While solving an Aristocrat, a partial word reads '_HE'. Which letter most commonly fills the blank in English?

Accepted Answer

T

Answer

'THE' is the most common English word, making T the overwhelmingly likely missing letter, though WHE- and SHE are possible alternatives.

Question 4

In a Morbit cipher (dot=1, dash=2), what two-digit number represents the Morse code for the letter A (dot-dash)?

Accepted Answer

12

Answer

Morse code for A is dot-dash (.-), which in Morbit dot=1/dash=2 notation becomes the pair 1-2, written as 12.

Question 5

A Codebusters timed event clue states: 'Caesar shift = number of letters in SCIENCE'. What is the shift value?

Accepted Answer

7

Answer

S-C-I-E-N-C-E contains 7 letters, so the Caesar shift is 7.

Codebusters Test Practice Test

Codebusters Test Practice Test

Codebusters Test Codebusters Pattern Recognition 5