- Convert to State Array
- Transformations (and inverses)
- AddRoundKey
- SubBytes
- ShiltRows
- MixColumns
- Key Expansion
1. Convert to state array
2a. AddRoundKey
2b. SubBytes (S-box)
for index 55, the s-box value is fc
2c. ShiftRows
2d. MixColumns
3. Key Expansion (new round key)
#AES round key (128 bits)current round key = w0, w1, w2, w3 (column, vertical)w0=column 1, w1 = c.2, w2 = c.3, w3 = c.4g(w3) calculation:
1) shift left, 2) apply s-box,
3) add round constant (01,00,00,00)new roundkey: w4, w5, w6, w7
w4 = w0 xor g(w3), w5 = w4 xor w1,
w6 = w5 xor w2, w7 = w6 xor w3
Example
Calculation of round key (round 1)
w3 = 01 02 14 13, shift left = 02 14 13 01, after s-box 77 fa 7b 7c, after + 1000h = 76 fa 7b 7c.
so g(w3) = 76 fa 7b 7c, then w4 = wo xor g(w3) = 74, fb 6a 7c (column one of round 1 key)
Algorithm
10 round = 128-bit keys
12 round = 196-bit keys
14 round = 256-bit keys
AES-256 is considered to be quantum resistant.
References:
1. Rijndael-Inspector - Rijndael_Animation_v4-eng.exe|swf - A flash application
2. AES-example.pdf
3. Zhou-Xuan-fulltext.pdf (Univ. of Manchester)
