A security analyst is comparing the Playfair and Vigenere ciphers for a training module. She wants to highlight a key difference in how they handle frequency analysis. Which statement is correct?

Vigenere hides digraph frequencies, while Playfair flattens single-letter frequencies

Playfair hides single-letter frequencies but preserves digraph patterns, while Vigenere flattens single-letter frequencies

Playfair is a polyalphabetic cipher, while Vigenere is a digraph cipher

Both ciphers are equally resistant to frequency analysis

A cryptanalyst is examining a ciphertext that has a frequency distribution very close to English, but the plaintext is known to be English. She suspects the cipher is either Playfair or a transposition cipher. Which observation would help her distinguish between the two?

The ciphertext has the same letter frequencies as English but the digraph patterns are unusual

The ciphertext has a flat frequency distribution

The ciphertext is twice as long as the plaintext

The ciphertext contains only the letters A, D, F, G, V, and X

A military historian is explaining the ADFGVX cipher to students. She states that the cipher combines two stages: a substitution using a 6x6 Polybius square and a transposition using a keyword. A student asks why the cipher uses only the letters A, D, F, G, V, and X in the ciphertext. What is the correct reason?

These letters are the most frequent in the German language, improving compression

These letters are the first six letters of the alphabet, simplifying the Polybius square

These letters are the only ones that can be transmitted by the field radio of the era

These letters were chosen because they are easily distinguished in Morse code, reducing transmission errors

EC-CouncilCertified Encryption Specialist

Domain 1Objective 2

Classical Ciphers (Caesar, Vigenere, Playfair, ADFGVX) ECES Practice Questions (Page 5)

Part of the Cryptography Foundations and History domain, which makes up ~16% of our current practice bank. EC-Council does not publish an official question count, but from its 120-minute exam (~50–80 total, ~8–13 in this domain), expect 3–4 from this objective — we provide 36 practice questions to prepare you well beyond it. (estimate)

36questions here

8free pages

5concepts

Questions 21–25

21application · medium
A developer is implementing a Vigenere cipher for a legacy system. The plaintext is 'HELLO' and the keyword is 'ABC'. What is the correct ciphertext?
Select an answer first
22expert · hard
A security analyst is comparing the Playfair and Vigenere ciphers for a training module. She wants to highlight a key difference in how they handle frequency analysis. Which statement is correct?
Select an answer first
23expert · hard
A cryptanalyst is examining a ciphertext that has a frequency distribution very close to English, but the plaintext is known to be English. She suspects the cipher is either Playfair or a transposition cipher. Which observation would help her distinguish between the two?
Select an answer first
24application · medium
A military historian is explaining the ADFGVX cipher to students. She states that the cipher combines two stages: a substitution using a 6x6 Polybius square and a transposition using a keyword. A student asks why the cipher uses only the letters A, D, F, G, V, and X in the ciphertext. What is the correct reason?
Select an answer first
25application · hard
A cryptography lab manual instructs students to encrypt the plaintext 'BALLOON' using a Playfair cipher with the key square built from the keyword 'MONARCHY'. The students must correctly apply the Playfair digraph rules. What is the correct ciphertext?
Select an answer first

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Classical Ciphers (Caesar, Vigenere, Playfair, ADFGVX) ECES Practice Questions (Page 5)

Questions 21–25

A developer is implementing a Vigenere cipher for a legacy system. The plaintext is 'HELLO' and the keyword is 'ABC'. What is the correct ciphertext?

A security analyst is comparing the Playfair and Vigenere ciphers for a training module. She wants to highlight a key difference in how they handle frequency analysis. Which statement is correct?

A cryptanalyst is examining a ciphertext that has a frequency distribution very close to English, but the plaintext is known to be English. She suspects the cipher is either Playfair or a transposition cipher. Which observation would help her distinguish between the two?

A cryptography lab manual instructs students to encrypt the plaintext 'BALLOON' using a Playfair cipher with the key square built from the keyword 'MONARCHY'. The students must correctly apply the Playfair digraph rules. What is the correct ciphertext?

Keep studying — Cryptography Foundations and History