Classical Ciphers (Caesar, Vigenere, Playfair, ADFGVX) ECES Practice Questions (Page 8)

Questions 36–36

1. 36expert · hard

   A security researcher is analyzing a historical ciphertext that was encrypted with the ADFGVX cipher. She knows the keyword used for the columnar transposition is 'GERMAN'. She has successfully recovered the intermediate string after the Polybius square substitution. What is her next step to recover the plaintext?

   • AApply the inverse Polybius square substitution to the intermediate string immediately
   • BUse Kasiski examination to find the transposition key
   • CWrite the intermediate string into a grid with 6 columns, then read out the columns in the order determined by the alphabetical order of the keyword letters
   • DPerform a frequency analysis on the intermediate string to identify the key length
   Reveal Solution Discussion Select an answer first