CS 772

Assignment #2

Due Midnight, Thursday Oct. 11, 2012

1. Show the result of the 1^st round of

1) DES

2) IDEA

3) AES-128

a. Assume all the bits of both the input block and the key are all 0s.

b. Assume all the bits of both the input block and the key are all 1s.

c. Assume all the bits of the input block are all 0s and the key are all 1s.

d. Assume all the bits of the input block are all 1s and the key are all 0s.

2. Here is the specification of a Simple Encryption Algorithm (SEA):

· The Input data block size and encryption key length is 4 bits and the number of rounds is 2.

The same key is used for the two rounds.

· The steps of each round are:

1. XOR the data block with the encryption key.

2. Substitute the result using the S-table.

3. Permute the output by swapping odd and even bits.

S-table

0000 0001

0001 0101

0010 1010

0011 0010

0100 1110

0101 1011

0110 1000

0111 0100

1000 1111

1001 0111

1010 0011

1011 1101

1100 0110

1101 1100

1110 0000

1111 1001

Use SEA to encrypt the message “1111 1111” with key “1111” and the IV “1111” according the following chaining methods:

1) ECB (Electronic Code Book)

2) CBC (Cipher Block Chaining)

3) OFB (Output Feedback Mode)

4) CFB (Cipher Feedback Mode)

5) CTR (Counter Mode)