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SSC CGL Coding Decoding — practice questions — page 4

Explore 95 free Coding Decoding questions in SSC CGL Reasoning. Open each question or exercise to read its content, reference answers and available explanation.

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Coding Decoding questions and exercises with answers

Showing questions 91–95 of 95.

In a Vigenère tabula recta, how does each successive row differ from the one above?Read the answer and worked solution →About how many bits of strength do the 26! possible substitution alphabets give?Read the answer and worked solution →By unicity distance, how many ciphertext letters are needed to crack a mixed alphabet substitution?Read the answer and worked solution →In a code each letter is replaced by the next letter in the alphabet. How is BAG written?Read the answer and worked solution →A code replaces each letter by the next one in the alphabet. What word does IBM stand for?Read the answer and worked solution →

Worked practice questions

In a Vigenère tabula recta, how does each successive row differ from the one above?

  1. Shifted one place left
  2. Reversed in order
  3. Randomly mixed up
  4. Shifted by 13 places
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Correct answer: A. Shifted one place left

The first row is the plain alphabet and every later row slides one more place to the left.

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About how many bits of strength do the 26! possible substitution alphabets give?

  1. About 26 bits
  2. About 13 bits
  3. About 676 bits
  4. About 88 bits
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Correct answer: D. About 88 bits

26 factorial is roughly 2 to the power 88, so the number of keys corresponds to about 88 bits.

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By unicity distance, how many ciphertext letters are needed to crack a mixed alphabet substitution?

  1. About 27.6
  2. About 2
  3. About 100
  4. About 6
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Correct answer: A. About 27.6

The unicity distance of English for a mixed alphabet is 27.6 letters of ciphertext.

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