Codebusters Test Graduation Requirements 3 — Questions and Answers
Question 1: Which cipher graduation requirement involves encoding plaintext using a keyword where each keyword letter shifts a column of the alphabet?
- Atbash cipher
- Vigenere cipher (Correct answer)
- Rail Fence cipher
- Polybius square
Correct answer: Vigenere cipher
The Vigenere cipher uses a repeating keyword where each letter defines the shift applied to corresponding plaintext letters.
Question 2: For the Codebusters national trial event, teams must decode an Aristocrat WITHOUT word divisions. What is this variant called?
- Xenocrypt
- Patristocrat (Correct answer)
- Cryptarithm
- Nihilist
Correct answer: Patristocrat
A Patristocrat is an Aristocrat-style monoalphabetic substitution cipher presented without spaces between words.
Question 3: When decoding a Caesar cipher, a graduation requirement basic skill, what is the maximum number of shift values a student must test?
- 13
- 25 (Correct answer)
- 26
- 52
Correct answer: 25
There are 25 possible non-zero shifts in a Caesar cipher (shifts 1 through 25), plus shift 0 which is no cipher at all.
Question 4: Which graduation requirement topic requires students to understand the Kasiski examination technique?
- Caesar cipher key recovery
- Finding the keyword length in a Vigenere cipher (Correct answer)
- Decoding a columnar transposition
- Solving a Polybius square
Correct answer: Finding the keyword length in a Vigenere cipher
The Kasiski examination finds repeated ciphertext sequences to determine the likely key length of a Vigenere or polyalphabetic cipher.
Question 5: In the Codebusters running key cipher, what is used as the key instead of a short repeating keyword?
- A random number table
- A passage from a known text (Correct answer)
- The plaintext itself reversed
- A Polybius square grid
Correct answer: A passage from a known text
A running key cipher uses a long passage from a book or known text as the key, making it non-repeating and harder to crack.
Question 6: What letter frequency is most important to identify first when solving an English Aristocrat, a core graduation competency?
- T
- A
- E (Correct answer)
- O
Correct answer: E
E is the most frequent letter in English text (~12.7%), making it the first target in frequency analysis of monoalphabetic substitution ciphers.
Question 7: Which Codebusters graduation requirement cipher uses a 5×5 grid to encode letters as pairs of coordinates?
- Rail Fence
- Vigenere
- Polybius square (Correct answer)
- Atbash
Correct answer: Polybius square
The Polybius square encodes each letter as a row-column coordinate pair using a 5×5 grid (typically combining I and J).
Codebusters Test Graduation Requirements 3
Which cipher graduation requirement involves encoding plaintext using a keyword where each keyword letter shifts a column of the alphabet?