A historian is analyzing a World War I field message encrypted with the ADFGVX cipher. She knows the cipher uses a 6x6 Polybius square and a columnar transposition with a keyword. She has intercepted a long ciphertext and suspects the transposition key length is 10. Which cryptanalytic technique should she apply first to confirm the key length?

Try all possible Polybius square permutations

Divide the ciphertext into 10 columns and look for patterns

Frequency analysis on the ciphertext letters

Kasiski examination on the ciphertext

A security trainer is demonstrating why a single substitution alphabet is weak. She encrypts the phrase 'ATTACK AT DAWN' with a Caesar shift of 4, producing 'EXXEGO EX HEAR'. She then asks trainees to identify the most efficient cryptanalytic method to recover the plaintext without knowing the shift. Which method should the trainees use?

Apply Kasiski examination to find the key length

Use a known-plaintext attack with the word 'ATTACK'

Perform a digraph frequency analysis on pairs of letters

Try all 25 possible shifts and look for readable text

A cryptanalyst is examining a long ciphertext that she believes was produced by a Vigenere cipher. She wants to determine the keyword length. Which cryptanalytic technique should she apply first?

Kasiski examination to find repeated sequences and their distances

Brute-force all possible keys of length 1 to 10

Frequency analysis on the entire ciphertext as a single alphabet

Index of coincidence on the ciphertext as a whole

A cryptanalyst is trying to break an ADFGVX cipher. She has captured a ciphertext of length 600 and suspects the transposition key length is 10. Which approach is most efficient to confirm the key length?

Perform a Kasiski examination on the ciphertext

Try all 26 possible Caesar shifts on the entire ciphertext

Arrange the ciphertext into 10 columns and perform frequency analysis on each column

Use the index of coincidence on the entire ciphertext

EC-CouncilCertified Encryption Specialist

Domain 1Objective 2

Classical Ciphers (Caesar, Vigenere, Playfair, ADFGVX) ECES Practice Questions (Page 1)

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 1–5

1application · hard
A historian is analyzing a World War I field message encrypted with the ADFGVX cipher. She knows the cipher uses a 6x6 Polybius square and a columnar transposition with a keyword. She has intercepted a long ciphertext and suspects the transposition key length is 10. Which cryptanalytic technique should she apply first to confirm the key length?
Select an answer first
2application · medium
A developer is implementing a Vigenere cipher for a legacy system. The keyword is 'CODE'. The plaintext is 'SECRET'. What is the correct ciphertext?
Select an answer first
3application · medium
A security trainer is demonstrating why a single substitution alphabet is weak. She encrypts the phrase 'ATTACK AT DAWN' with a Caesar shift of 4, producing 'EXXEGO EX HEAR'. She then asks trainees to identify the most efficient cryptanalytic method to recover the plaintext without knowing the shift. Which method should the trainees use?
Select an answer first
4application · medium
A cryptanalyst is examining a long ciphertext that she believes was produced by a Vigenere cipher. She wants to determine the keyword length. Which cryptanalytic technique should she apply first?
Select an answer first
5application · hard
A cryptanalyst is trying to break an ADFGVX cipher. She has captured a ciphertext of length 600 and suspects the transposition key length is 10. Which approach is most efficient to confirm the key length?
Select an answer first

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Classical Ciphers (Caesar, Vigenere, Playfair, ADFGVX) ECES Practice Questions (Page 1)

Questions 1–5

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

A cryptanalyst is examining a long ciphertext that she believes was produced by a Vigenere cipher. She wants to determine the keyword length. Which cryptanalytic technique should she apply first?

A cryptanalyst is trying to break an ADFGVX cipher. She has captured a ciphertext of length 600 and suspects the transposition key length is 10. Which approach is most efficient to confirm the key length?

Keep studying — Cryptography Foundations and History