Assignment #3 - 6 points - deadline April 29, 23:59
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The third assignment deals with modes of operation for block ciphers. 
You might want to use some quite basic schematic description of three
basic modes of operations for block ciphers, e.g. from
ftp://ftp.prenhall.com/pub/esm/computer_science.s-041/stallings/Figures/Security2e-Figures/CHAP-3.zip

Additional reading that might be perhaps useful is the NIST "Special Publication" SP 800-38A
"Recommendation for Block Cipher Modes of Operation - Methods and Techniques"
at http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf. 
Even more information on all the modes (both approved and considered) is at the
NIST mode of operation webpage http://csrc.nist.gov/CryptoToolkit/modes/.



QQQ3:
=====  6 points, deadline April 29, 23:59


3.1 Cipher Block Chaining (2 points)

3.1.1 How does a system working in this mode recover 
from a block of ciphertext being lost at transfer?

3.1.2 Discuss error propagation of one bit error in the ciphertext 
in terms of its impact on the decrypted plaintext.


3.2 Cipher Feedback mode (2 points)

3.2.1 How does a system working in this mode recover 
from a block of ciphertext being lost at transfer?

3.2.2 Discuss error propagation of one bit error in the ciphertext 
in terms of its impact on the decrypted plaintext.


3.3 Output Feedback mode (2 points)

3.3.1 How does a system working in this mode recover 
from a block of ciphertext being lost at transfer?

3.3.2 Discuss error propagation of one bit error in the ciphertext 
in terms of its impact on the decrypted plaintext.

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