Understanding Cryptography by Christof Paar and Jan Pelzl - Chapter 3 Solutions - Ex3.2
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- Exercise 3.1
- Exercise 3.2
- Exercise 3.3
- Exercise 3.4
- Exercise 3.5
- Exercise 3.6
- Exercise 3.7
- Exercise 3.8
- Exercise 3.9
- Exercise 3.10
- Exercise 3.11
- Exercise 3.12
- Exercise 3.13
Exercise 3.2
We want to verify that \(IP(·)\) and \(IP^{−1}(·)\) are truly inverse operations. We consider a vector \(x = (x_1,x_2,...,x_{64})\) of 64 bit.
Show that \(IP^{−1}(IP(x)) = x\) for the first five bits of \(x\), i.e. for \(x_i, i = 1,2,3,4,5\).
Solution
I haven’t yet verified this solution independently. If you spot any mistakes, please leave a comment in the Disqus box at the bottom of the page.
The easiest way to demonstrate this is to create a table that shows which location each bit gets mapped to after each operation:
Thomas Busby
I write about computing stuff