Mercy College Cryptography Programing Project

CryptographyAssignment – Mode of Operations
Problem 1 Let 𝐸 be a block cipher of block length 4 and suppose that 𝐸𝑘(𝑏1𝑏2𝑏3𝑏4) = (𝑏2𝑏3𝑏4𝑏1).
Encrypt 𝑚 = 1011 0001 0100 and decrypt the ciphertext with the following operation modes: a)
ECB, b) CBC mode with IV = 1010, c) CTR mode with ctr = 1010.
Problem 2 Compare ECB, CBC and CTR modes with respect to message expansion, error
propagation, pre-computations and parallelization of encryption and decryption.
Problem 3 Do the following when encryption works on letters. Suppose we have a shift cipher
with k = 2, in which we restrict the possible letter to A-P. Suppose A-P is represented as 00001111 as follows
A
B
C
D
E
F
G
H
0000
0001
0010
0011
0100
0101
0110
0111
I
J
K
L
M
N
O
P
1000
1001
1010
1011
1100
1101
1110
1111
Given the Plaintext=HELLO, calculate the ciphertext with the following operations.
a) ECB mode
b) CBC mode with IV = 0010
c) Counter mode with I1 = 0001
d) OFB mode with IV = 0010
e) CFB mode with IV = 0010
Problem 4. Read and test AES code. In this exercise, students are asked to run the AES code
using file based two separate actions demonstrated in the class. Students are encouraged to use
other crypto package and codes. The data is your name plus your WID. Screenshots the code and
the results (file generated).