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#
# sbox.m
#
# (c) 2021 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
#
A=[
1,0,0,0,1,1,1,1;
1,1,0,0,0,1,1,1;
1,1,1,0,0,0,1,1;
1,1,1,1,0,0,0,1;
1,1,1,1,1,0,0,0;
0,1,1,1,1,1,0,0;
0,0,1,1,1,1,1,0;
0,0,0,1,1,1,1,1;
]
R = zeros(8,16);
R(:,1:8) = A;
R(:,9:16) = eye(8);
for k = (1:5)
for i=(k+1:8)
pivot = R(i,k);
R(i,:) = R(i,:) + pivot * R(k,:);
end
R = mod(R, 2)
end
P = [
1,0,0,0,0,0,0,0;
0,1,0,0,0,0,0,0;
0,0,1,0,0,0,0,0;
0,0,0,1,0,0,0,0;
0,0,0,0,1,0,0,0;
0,0,0,0,0,0,0,1;
0,0,0,0,0,1,0,0;
0,0,0,0,0,0,1,0;
]
R = P * R
for k = (8:-1:2)
for i = (1:k-1)
pivot = R(i,k);
R(i,:) = R(i,:) + pivot * R(k,:);
end
R = mod(R, 2)
end
B = R(:,9:16)
A * B
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