Which are the weaknesses of a shift cipher?

Part I (Each 4 Pts. Total 40.) Choose the best one. Please provide reason of your choice in a few sentences or reasons not choosing the other choices. Reason must be in your own words. Use guidelines for reference as given in the instructions.

1. To protect information, it is sufficient to protect against possible virus threats: True/False justify your answer
2. Which are the weaknesses of a shift cipher?
   A. Natural language letter frequency makes them easy to decode.
   B. The number of letters in the alphabet makes them easy to decode.
   C. Once the shift is determined the message is decoded.
   D. Once you have the code book you can decode the message instantly
   E. A&B
   F. A, B & C
   G. A, B, C and D
   H. A & C
   No reason required.
3. What is the basis of the modern cryptography? _____
   A. the laws of mathematics
   B. manipulation of data
   C. creating disguises for information
   D. none of the above
   Reason:
4. Historically, the primary and compelling reason for advances in cryptography has been _.
   a. protecting business assets
   b. the need for individual privacy
   c. wars
   d. keeping diplomatic conversations secret
   Reason: _
5. A ___ requires that the cipher alphabet changes throughout the encryption process.
   a. monoalphabetic substitution cipher
   b. polyalphabetic substitution cipher
   c. quantum cipher
   d. alphanumeric shift cipher
   Reason: _
6. one of the Network threats is
   A. buffer overflow
   B. slowing the computer
   C. denial of service
   D. computer lock up
   how does it happen: _
7. Risk is _. A. a weakness in the system B. a circumstance that may cause loss or is possible danger C. is a vulnerability that can be exploited D. Nothing to worry about Reason:
8. The trustworthiness of a system is diminished because of.
   a. exposure to risks
   b. demand for keys
   c. confidence decreases
   d. bad weather
   Reason: _
9. The _ controls the action of the algorithm.
   a. The receiver
   b. the length of the plain text
   c. cipher text
   d. key
   Reason:
10. What has become a major web problem with respect to security?
    a. scripting errors
    b. mapping attacks
    c. on-line surveys
    d. user ignorance

Reason: _

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