Codebusters Test Codebusters Pattern Recognition 3 — Questions and Answers
Question 1: In a Xenocrypt (Spanish-language Aristocrat), which letter is typically the most frequent in the ciphertext?
- E (Correct answer)
- Q
- W
- K
Correct answer: E
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?
- THE (Correct answer)
- AND
- FOR
- HIS
Correct answer: THE
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?
- Shift 23, because CVC is a valid consonant-vowel-consonant syllable pattern (Correct answer)
- Shift 4, because BUX contains a vowel
- Shift 13 (ROT13) is always correct
- Both are equally likely
Correct answer: Shift 23, because CVC is a valid consonant-vowel-consonant syllable pattern
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?
- TE (Correct answer)
- ET
- AT
- IT
Correct answer: TE
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?
- B (Correct answer)
- A
- M
- T
Correct answer: B
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.
Question 6: A 6-letter ciphertext word has pattern ABCABD (positions 1 and 4 share a letter). Which English word fits this pattern?
- REFERS (Correct answer)
- SIMPLE
- BRIDGE
- SMOOTH
Correct answer: REFERS
REFERS has R at positions 1 and 5 and E at positions 2 and 4, sharing repeated letters at multiple positions unlike the all-unique SIMPLE.
Question 7: Which word pattern would you expect most often at the START of a ciphertext sentence in an Aristocrat?
- A 3-letter high-frequency group matching THE (Correct answer)
- A 5-letter group matching ABOUT
- A 2-letter group matching IT
- A 4-letter group matching THEM
Correct answer: A 3-letter high-frequency group matching THE
'THE' is the most common English word and frequently begins sentences, making its 3-letter ciphertext pattern the primary sentence-start target.
Codebusters Test Codebusters Pattern Recognition 3
In a Xenocrypt (Spanish-language Aristocrat), which letter is typically the most frequent in the ciphertext?