# 2-round generalized Feistel network

Write the decryption of a 2-round generalized Feistel network given below.

$P_i$ denotes plaintext blocks of each 32-bits.
$RK_i$ denotes the round keys.
$WK_i$ denotes 32-bit keys applied only at the ﬁrst round (whitening keys)

Continue the lines for the decryption.

The whole ﬁgure will input 4, 32-bit plaintext, encrypt it for 2 rounds and continue with decryption and will output the same input

Can anyone help me for this question?

• What have you tried? We generally don't provide much help for people who just do homework dumps on us, with no sign of effort on their part. Dec 29, 2016 at 18:55
• @poncho İ didn't do so i want to learn. Dec 29, 2016 at 18:59
• If two rounds are too tough, why don't you try to invert a single round? Dec 29, 2016 at 19:41
• I didnt do anything i tried but Dec 30, 2016 at 21:12

Let $X_{1,i},i=0,\ldots,3$ be the 32-bit outputs of the first round, before the swap, numbered left to right. Then,
$$P_2=X_{1,2}, \quad P_0=X_{1,0}$$ and $$P_1=WK_0\oplus F_0(RK_0,X_{1,0})\quad P_3=WK_0\oplus F_0(RK_1,X_{1,2}),$$ The equations for the $P_{i}$ are as above.