Preview

08 - Vernam cipher

 1. The Vernam cipher is named after its inventor Gilbert Vernam.

  TRUE

  FALSE

 2. The cipher was originally invented to scramble text transmitted by …
vernam_q2.png

  radio broadcast

  telegram

  teleprinter

  email

 3. How was the Vernam cipher key originally fed into the system?

  by a floppy disk

  via the Internet

  by tape with punched holes

  by manual input

 4. The Russian engineer Vladimir Kotelnikov proved the cipher was unbreakable if the key was …

  also encrypted

  sufficiently long

  truly random and not repeated

  very short

 5. The principles were developed into a manual encryption system known as the …

  one use cipher

  one time pad

  one chance book

  once said report

 6. Why is the Vernam cipher not vulnerable to frequency analysis?

  As the ciphertext can be transmitted very quickly

  As each plaintext character is transposed by a random number

  As each plaintext character is transposed by a fixed number

  As the length of the key makes it difficult to compute

 7. The Vernam cipher uses an XOR logical operation. What does this mean?

  The output is false only if both inputs are different

  The output is true only if both inputs are the same

  The output is true only if one input is true and the other is false

  The output is true only if both inputs are false

 8. XOR could also be written as …

  A or B or A and B

  A or B but not A and B

  A or B

  A and B but nor A or B

 9. An algorithm can generate a truly random key number.

  FALSE

  TRUE

 10. Using binary and XOR, how would 10101 appear in ciphertext if the key is 00110?

  11110

  11100

  10001

  10011