1. Key Expansion Key size = 192 bits = 6 x 32 bits = 6 words (Nk=6)
Round key size = 128 bits
ki – 32-bit words k0 k1 k2 k3 k4 k5
Key K k0 k1 k2 k3 k4 k5 k6 k7 k8 k9
k10
k11
k12
k13
k14
k15
k16 ….
Round Key 0 K0
Round Key 1 K1
Round Key 2 K2
Round Key 3 K3 ….
4 words

2. Key Expansion (1) ki = ki-Nk  ki-1 Nk=6 …. k0 k1 k2 k3 k4 k5 k6 k7 k8

3. Key Expansion (2) ki = ki-Nk  f(ki-1) Nk=6 …. RotWord
RotWord(a,b,c,d)=(b,c,d,a)
SubWord
SubWord(a,b,c,d)=(S[a],S[b],S[c],S[d])
Rcon[i/Nk] f
Rcon[j] = (e[j], 00,00,00)
ki = ki-Nk  f(ki-1)

4. Pseudocode for Key Expansion
Using Notation from the Homework Specification
for i=0 to Nk-1 do
ki = wi
end for
for i=Nk to (r+1)*4-1 do
if i mod Nk = 0 do
ki = ki-Nk ⊕ SubWord(RotWord(ki-1)) ⊕ Rconi/Nk
elsif Nk=8 and i mod Nk = 4 do
ki = ki-Nk ⊕ SubWord(ki-1)
else
ki = ki-Nk ⊕ ki-1
end if

5. Block Diagram
Notation:
Sub = SubWord
Rot = RotWord

6. Pseudocode for Key Expansion
Using Notation from the Key Expansion Examples