CSci 4509 Cryptographic Protocols -- Problem set 2.
Problem 1: encrypting with SPN (7 points)
Consider the SPN in example 3.1 (the one that we considered in
class). Suppose the key for the SPN is changed to
What would be the encryption of the plaintext
K = 1011 0101 1100 0101 1001 1110 1011 0010
using this key? Please show ALL your intermediate results (i.e. w, u,
and v at each level). You may compute the encryption by hand or write
x = 0010 0110 1011 0111
Problem 2: decrypting with SPN (4 points)
Exercise 3.1 p. 113.
Problem 3: linear cryptanalysis of SPN (question (a) 4 points, the
rest extra credit)
Exercise 3.14 p. 115 questions a, b, and c only.
Problem 4: cryptanalysis of DES (8 points)
Exercise 3.10 p. 115. Important modification: you may compute the bias of
this variable for any 2 DES S-boxes if you are working by yourself, and
for any 4 DES S-boxes if you are working as a team of two. Please
submit all the intermediate results.
Problem 5: modes of operation of block ciphers (4 points)
Exercise 3.7 p. 114.
Problem 6: AES (8 points)
Exercise 3.5: construct the first 4 keys only.
Use the palintext given in exercise 3.6 and compute only the beginning
of encryption of this text with AES: perform AddRoundKey, SubBytes,
and ShiftRows (since we didn't talk about the exact algorithm for
MixColumns, you don't need to perform that step).
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