Only if you know the scheme, seed, and samples of the resulting stream
of data. There's no way you can catalog all the data to match the
pattern, so you have to know the starting point. So while it's not
random, it's not easy to figure out what the next value is going to be.
If you want to be pedantic, I did NOT say that it was random.

I'm sure there are theoretical attacks on large LFSRs. You could hash
the output with a good hashing algorithm. Or you could use some sort of
hybrid s-box feedback instead of a XOR. It wouldn't be linear like an XOR.

--
Martin K


David VanHorn wrote:
> On 10/9/07, Martin Klingensmith <martin@nnytech.net> wrote:
>> Then use a 256 bit LFSR. It's still easier than using a radioactive source.
>>
>> 2^(256)-1 steps before it repeats.
> 
> 
> But completely and absolutely NOT random.
> This is how "rolling code" units work.
> If I know the length of the register, and I know a couple of
> sequential bytes, then I can predict the entire future and past.
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