Messages in this thread |  | | From | Stephan Mueller <> | Subject | Re: random.c: LFSR polynomials are not irreducible/primitive | Date | Wed, 16 Aug 2017 14:51:42 +0200 |
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Am Dienstag, 15. August 2017, 17:12:24 CEST schrieb Theodore Ts'o:
Hi Theodore,
> > Stephan, if you have any comments on the proposal made by David > Fontaine and Olivier Vivolo, I'd appreciate hearing them!
I think I have some news: The magma code I used for GF(2^32) testing was not correct.
The corrected magma code is attached (thanks to Dr. Peter Birkner, BSI, who helped me here).
That magma code shows:
- the current polynomials for Q(X) = α**3 (P(X) − 1) + 1 are irreducible but not primitive over GF(2^32)
- the polynomials suggested in https://eprint.iacr.org/2017/726.pdf Q(X) = α**4 (P(X) − 1) + 1 are both, irreducible and primitive over GF(2^32)
The use of GF(2^32) is important, because we apply the LFSR to a 32 bit word. Hence, we have 2^32 permutations the LFSR should evenly cover.
Bottom line, I would recommend that random.c is patched to take the polynomials suggested in https://eprint.iacr.org/2017/726.pdf.
If it is of any help, the attached magma code could be preserved somewhere useful (in random.c?)
Ciao Stephan[unhandled content-type:application/x-wine-extension-mag] |  |