Karim Belabas on Sun, 09 Dec 2007 18:25:13 +0100

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Re: FFELT: how to recover the field?

* Jeroen Demeyer [2007-12-09 16:31]:
> Hello list,
> Given a FFELT x in characteristic p, I would like to compute a p-th root of 
> x.

What's wrong with sqrtn(x,p) ?

> The most obvious way to do this is to compute x^(p^(n-1)), where p^n is 
> the cardinality of the field.  However, how can I recover p


> and n given only the FFELT?  Obviously, it suffices to get the
> polynomial defining the finite field (i.e. the argument given to
> ffgen()).  I tried x.mod, but that doesn't work.

It doesn't seem to be possible currently (only x.p and x.pol work).
I'll add x.mod to the allowed member functions 


Karim Belabas                  Tel: (+33) (0)5 40 00 26 17
Universite Bordeaux 1          Fax: (+33) (0)5 40 00 69 50
351, cours de la Liberation    http://www.math.u-bordeaux.fr/~belabas/
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