Codebusters Test Codebusters Pattern Recognition 3

Question 1

In a Xenocrypt (Spanish-language Aristocrat), which letter is typically the most frequent in the ciphertext?

Accepted Answer

E

Answer

Like English, Spanish has 'E' as its most frequent letter (~14%), so it remains the primary target in Xenocrypt frequency analysis.

Question 2

A 3-letter ciphertext sequence 'MNK' appears 8 times in a 200-character message. What should you suspect it represents?

Accepted Answer

THE

Answer

THE is the most common English trigraph; a high-frequency 3-letter ciphertext sequence almost always maps to 'THE' in substitution ciphers.

Question 3

When testing Caesar shifts, shift 4 gives 'BUX' and shift 23 gives 'CVC'. Which is more likely a correct decode?

Accepted Answer

Shift 23, because CVC is a valid consonant-vowel-consonant syllable pattern

Answer

CVC is a common English syllable structure, while BUX is not a recognizable English word, making shift 23 the stronger candidate.

Question 4

In an Aristocrat, you know ciphertext Z=T and ciphertext T=E. A ciphertext word reads 'ZT'. What does it decode to?

Accepted Answer

TE

Answer

Substituting in order: Z→T and T→E gives the plaintext sequence T-E, spelling 'TE'.

Question 5

In a K1 alphabet cipher with keyword 'MATH', what letter does ciphertext 'A' (second cipher position) decode to?

Accepted Answer

B

Answer

In a K1 alphabet, the keyword fills the cipher-to-plain mapping starting at A; M=A, A=B, T=C, H=D — so cipher A maps to plaintext B.

Codebusters Test Practice Test