Bill Allombert on Sun, 09 Dec 2007 20:16:46 +0100 |
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Re: FFELT: how to recover the field? |
On Sun, Dec 09, 2007 at 05:03:52PM +0100, Bill Allombert wrote: > On Sun, Dec 09, 2007 at 04:15:46PM +0100, Jeroen Demeyer wrote: > > Hello list, > > > > Given a FFELT x in characteristic p, I would like to compute a p-th root > > of x. The most obvious way to do this is to compute x^(p^(n-1)), where > > Why are sqrtn(x,p) and x^(1/p) less obvious ? > > > 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. > > I think x.mod should be made to work, but I did not implement it because > I was not sure whether x.mod should return a polynomial with t_INT or > t_INTMOD coefficients (mod p). Done in CVS. I decided to return t_INT coefficient, since that closer to the internal representation and .mod is a member function. Cheers, Bill.