Unformatted text preview: CS172‐CS283 Quiz 2 ‐ 20090929 Student Name 1. Complete the following sentence: Student GWU Email Address In a stream cipher a ________________is mathematically combined (exclusive or’ed) with the plain text to produce the ciphertext. 2. State how is a block cipher different from a stream cipher ___________________________________________________________________________________________ 3. State how a block cipher is different from a classical cipher such as the Affine, Ceasar, or Vigenere cipher: __________________________________________________________________________________________ 4. Complete the following (Ø = totient): Ø(35) = ____________ 5. State three ways in which the Advanced Encryption Standard (AES) cipher and the Data Encryption Standard (DES) cipher are similar in terms of their respective algorithm; ____________________________________ ____________________________________ ____________________________________ 6. State three ways in which the AES cipher and the DES cipher are different in terms of their respective algorithm: ____________________________________ ____________________________________ ____________________________________ 7. What is a Linear Feedback Shift Register (LFSR) attempting to approximate when it is used in a Stream Cipher? _______________________________________________ 8. What is the output of an LSFR called when used in a stream cipher? _______________________________________________ 9. Name a widely used stream cipher that does NOT use a LSFR in its cipher algorithm. __________________________ 10. What kind of attack is the Diffie‐Hellman key agreement protocol vulnerable to??? ________________________________ CS172‐CS283 Quiz 2 ‐ 20090929 Page 1 CS172‐CS283 Quiz 2 ‐ 20090929 11. Convert the number 2010 to A) Hexadecimal (base 16): ______________________ B) Binary (base 2): _____________________ 12. What is the size of the block (in bits) of cleartext input to the AES cipher? ______________________ 13. How Many cryptographic cipher key sizes does the AES cipher support? ________________ 14. What are the cryptographic cipher Key Sizes that AES supports? ________________ 15. Complete the following sentence: In the DES cipher, each S‐Box has _______input bits and __________output bits 16. List the security services from the IEEE 802.11 Wired Equivalent Privacy standard that are compromised (i.e. “broken”)_______________________________________________ 17. What new Encryption cipher does the IEEE 802.11i (also known as Wireless Protected access 2 or WPA2) implement?________________________ 18. What security service is the Michael function (MIC) attempting to provide in the WPA and WPA2 wireless security standard?_________________________ 19. Julius Ceasar’s bad crypto day improves. Alice informs Julius that, even though his idea about using the Affine cipher is flawed, it turns out that there is an even better cipher which she became aware of through the Oracle and futurist, RR. This cipher uses two cryptographic keys, one that is public and known to all and a second, that is a private key, that is known only to the owner of the corresponding public key. The cipher is, in fact, now known as the RSA Cipher. Alice explains the cipher to Julius and provides him with his keys (without casting her eyes on the private key). If Julius’s public key is (n,a) and his private key is b. then please answer these questions about this interesting and new (to Julius) cipher 19.1. Write the mathematical representation of how one of Julius Ceasar’s field generals would encipher a message m to Julius using this RSA cipher.____________________________ 19.2. Now write the mathematical representation of how Julius would decipher ciphertext, c, to produce the plaintext:________________________________________ 19.3. And, finally, Write the mathematical relationship between a, and b.__________________________ CS172‐CS283 Quiz 2 ‐ 20090929 Page 2 ...
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- Spring '09
- Computer Security, Prime number, stream cipher