Question

Please show the initial round (i.e., round 0) when encrypt the following plaintext using AES: (I have shown each step, please fill in each form) Plaintext: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F Key: 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 Both plaintext and key are 16 bytes in hexadecimal. a) Original contents of state (hint: please transfer the plaintext block to state): b) Initial AddRoundKey: State ⨁ Key c) SubBytes d) ShiftRows MixColumns is NOT required.

Answer 1

Plaintext: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

Key: 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01

a). Original contents of state

00	04	08	0C
01	05	09	0D
02	06	0A	0E
03	07	0B	0F

Key

01	01	01	01
01	01	01	01
01	01	01	01
01	01	01	01

b). Initial AddRoundKey: It is XOR of Original State and Key.

01	05	09	0D
00	04	08	0C
03	07	0B	0F
02	06	0A	0E

c). SubBytes: To perform sub bytes, we use predefined S-Box. First character become row and second become column.

7C	6B	01	D7
63	F2	30	FE
7B	C5	2B	76
77	6F	67	AB

d). ShiftRows: Here, we will do right shift.

In first row, we are not shifting.

In second row, we shift one place further.

In third row, we shift two place further.

In fourth row, we shift three place further.

7C	6B	01	D7
F2	30	FE	63
2B	76	7B	C5
AB	77	6F	67