give me some explanation about the code.

function ab=poly_mult(a,b,mod_pol)
ab=0;
for i_bit=1:8
if bitget(a,i_bit)
b_shift=bitshift(b,i_bit-1);
ab=bitxor(ab,b_shift);
end
end
for i_bit=16:-1:9
if bitget(ab,i_bit)
mod_pol_shift=bitshift(mod_pol,i_bit-9);
ab=bitxor(ab,mod_pol_shift);
end
end

Answer 1

[Jan]

It is much more likely that you get a helpful answer, if you try to formulate with a certain level of politeness. Currently we see the command "give me" and an unformatted pile of code. If you follow the "? Help" link, you find instructions for formatting, and inserting a detailed question, which contains a "please" would be a good idea also. Currently it is not clear, if you ask e.g. for an explanation of the "function", "for" or "if" commands also. And it is not clear, if you took the time to read the corresponding documentation already: It would not be efficient, if we rephrase the contents of "help bitget" etc, when you have this information locally on your hard disk already.

Answer 2

[Image Analyst]

Usually when I've been seeing bitshift() and similar bit operations, it has to do with watermarking or steganography. Further low level details can be learned by reading the help for those functions, as Jan said, and then trying it with a known number to see what happens to its value as you do the operations. Do you know nothing about this code? Why are you concerned with it then?