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
K = 1011 0101 1100 0101 1001 1110 1011 0010
What would be the encryption of the plaintext
x = 0010 0110 1011 0111
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
an implementation.
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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