CS 472
Assignment #3
Due Midnight, Thursday Oct. 15, 2009
In this
assignment show your results in HEX. Show the results of all the
intermediate steps.
I.
Show
the result of the 1st round of DES
if the input data block is:
FF81 8181 8181 81FF and the encryption key is all 1s.
II.
Repeat
I. for IDEA if both the key and the
input data block are all 0s.
III.
Repeat
I. for AES-128 if both
the key and the input data block are all 1s.
IV.
Here
is a trivial encryption algorithm (TEA) consisting of a single round.
The Input data block size
and encryption key length is 4 bits.
1. Permute the input data block by moving a bit
from position i to position (i+2)
mod 4.
2. XOR the permuted data block with the
encryption key.
3. Substitute the result using:
|
Substitution Table |
|
0
1 |
|
1
5 |
|
2
A |
|
3
2 |
|
4
E |
|
5
B |
|
6
8 |
|
7
4 |
|
8
F |
|
9
7 |
|
A
3 |
|
B
D |
|
C
6 |
|
D
C |
|
E
0 |
|
F
9 |
Use the described TEA algorithm to encrypt the message: “AA” according the
following chaining methods, assuming the IV
is “C” and the key is “D”.
1.
ECB (Electronic Code Book)
2.
CBC (Cipher Block Chaining)
3.
OFB (Output Feedback Mode)
4.
CFB (Cipher Feedback Mode)
5.
CTR
(Counter Mode)
To make sure that your
answers are correct decrypt
your final results back to the original input message.
Submit your answer as described in Assignment #2 (but replace A1 with A3).
A shell
script is used to grade the assignment & it is
case and name sensitive.