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2answers
384 views

Why should we append zeros during CRC calculation?

Say we have M as message bits , why do we need to append r-zeros to M message bits before performing the division to obtain r-bit checksum. Why don't we directly perform the division on the M message ...
1
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1answer
139 views

Can every periodic binary sequence be expressed as the output of a Linear or Non-Linear Feedback Shift Register?

Quick background: The output of a Linear Feedback Shift Register (LFSR) with $n$ taps is a binary sequence which is periodic of length dividing $2^n-1$. From a mathematical point of view, such a ...
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1answer
44 views

Multiplication over $F_{2^{31}-1}$ by power of $2$

I'm reading the source code of a stream cypher (zuc): I cannot understand properly why they define the multiplication by power of 2 in this way: ...