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Re: (tye)Re: LFSR golf

by jepri (Parson)
on May 08, 2001 at 11:29 UTC ( [id://78774] : note . print w/replies, xml ) Need Help??

in reply to (tye)Re: LFSR golf
in thread LFSR golf

You repeat this process forever, producing a somewhat random stream of bits as a result.

It might be better if you said a 'disordered' stream, or 'complicated', 'lacking pattern'

The output is not random because it will be the same for the same initial setting of the register (like the 'random' number generator on most computers)

I didn't believe in evil until I dated it.

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(tye)Re2: LFSR golf
by tye (Sage) on May 08, 2001 at 18:57 UTC

    Like you mentioned, so-called "pseudorandom" number sequences are also identical for the same initial seed. I felt that "somewhat random" was less strong of a statement than "pseudorandom", but I can see where others would disagree. So I probably should have just stuck with "pseudorandom".

    For what it's worth, I find "disordered" and "lacking pattern" worse (the bits have a definite pattern and order). ;)

    This reminds me that I forgot to mention that the bit stream from a single LFSR has been studied to the point that a small subseries of bits is enough to predict the entire series. However, two carefully chosen LFSRs where each bit from one is used to determine whether the next bit from the other will be output or thrown away has been analyzed and found to be cryptographically strong.

            - tye (but my friends call me "Tye")