CSCI 391: Practical Cryptology
Spring 2015
Quiz 1

Each question - 10 points. Total 100 points. IN ALL QUESTIONS: Explain your answer
ALL MATERIAL IS OPEN.
You can use Wolfram|Alpha: Computational Knowledge Engine

1. Calculate and explain your calculations:

   -19 % 4 =

2. Encrypt the message MEETINGS using Vigenere Cipher and the keyword POOR. What are the cipherletters corresponding to both letters E? Did you get the same letter? Explan your answer.

3. Suppose you are using Shift Cipher and your plaintext is MEETINGS. What key you would need to use in order to encrypt letter N by letter Z?

4. Suppose you are using Vigener Cipher and your plaintext is ADVANCES. Give an example of the keyword to encrypt all letters A by the different letters. Explain.

5. Suppose you are using Vigener Cipher and the plaintext is ADVANCES. Give an example of the keyword to encrypt all letters A by the same cipherletter.

6. Suppose you are using Vigener Cipher and the plaintext is UTILITIES. Give an example of the keyword to encrypt all letters T by the same cipherletter M.

7. Suppose you are using Affine Cipher, and you know that decryption formula is Plain=7*(Cipher-9)%26. Find encryption formula.

8. Suppose you are using Affine Cipher, and you know that plaintext letter J corresponds to cipherletter X and you know that keyA = 7. Find keyB.

9. Suppose you are using Affince Cipher, and you know that plaintext letter B corresponds to letter Y and you know keyB = 13. Find keyA.

10. Decrypt the message XF that was ecnrypted by Shift Cipher with key K = 17. EXPLAIN YOUR CALCULATIONS!