Linear_approximation_table_script

This is my University work from cryptography course. This is a script, which takes an subtitution, and creates a linear approximation table for it. In cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers. Linear cryptanalysis is one of the two most widely used attacks on block ciphers; the other being differential cryptanalysis.

Example:

For following substitution (5,8,1,13,10,3,4,2,14,15,12,7,6,0,9,11) Script created following exel table, which can be used for linear cryptoanalysis:

0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
0	8	0	0	0	0	0	0	0	0	0	0	0	0	0	0
1	0	-2	-2	0	2	0	4	-2	2	0	0	2	4	2	-2
2	0	-2	0	-2	4	2	0	-2	-2	0	-2	0	-2	0	2
3	0	0	2	-2	-2	-2	0	-4	4	0	-2	-2	-2	2	0
4	0	-4	2	-2	0	-4	-2	2	0	0	2	2	0	0	-2
5	0	2	0	-2	2	-4	2	0	-2	-4	-2	0	0	-2	0
6	0	-2	2	0	0	-2	2	0	-2	4	0	-2	2	0	4
7	0	0	4	0	2	2	2	-2	0	0	4	0	-2	-2	-2
8	0	4	2	-2	0	0	2	2	0	4	-2	2	0	0	-2
9	0	2	0	-2	2	0	-2	0	-2	0	2	0	0	6	0
10	0	-2	2	0	0	2	-2	0	-2	0	-4	-2	2	0	-4
11	0	0	-4	0	2	-2	-2	-2	0	4	0	0	-2	-2	-2
12	0	0	0	0	-4	0	0	-4	-4	0	0	4	0	0	0
13	0	-2	-2	0	-2	0	4	2	-2	0	0	-2	-4	2	-2
14	0	-2	0	-2	0	2	0	2	2	0	-2	4	-2	0	2
15	0	0	2	6	2	-2	0	0	0	0	-2	2	-2	2	0