a) Describe the high level steps involved for decryption using a Feistel cipher. [ Your answer should go here]

b) Modify the pseudo code provided in the lecture notes that describe encryption using a Feistel network to do decryption. You need to actually rewrite the code. Use different font colors and comments to highlight the areas of the code you have changed.

Following is the encryption code for reference; you need to modify to perform decryption.

Literal MaxRound=16 # Number of Encryption rounds EndLiteral

BitRange LeftBits= 0, 31 # Total block is 64 bits wide. # Left side is bits 0 - 31 RightBits=32, 63 # Right side are bits 32 - 63 EndBitRange

TempText=PlainText # Size of Plain Text is 64 bits n=1 # Set subkey value to the 1st round # The key [n] represents the sub-key # derived from the key

while n <= MaxRound #Complete 16 rounds do ResultOfRound = RoundFunction (key [n], TempText ) IntermediateValue = TempText XOR ResultOfRound TempText = TempText TempText = IntermediateValue n = n + 1 done

#After last round there should not be any swapping of the # data block halves. Therefore undo the last swap done in # the while loop CipherText = TempText CipherText = IntermediateValue