RE: Your help needed

["Kaz Kobara" <k-kobara@aist.go.jp>]

> By curiosity, how did you compute factor(N) ?

We are interested in only small h=N/n and prime order n.
So we accept only N s.t. N/h is a prime number for small h.
This can be checked using isprime(N/h) == 1 for small h.

Kaz

> -----Original Message-----
> From: Bill Allombert [mailto:Bill.Allombert@math.u-bordeaux1.fr]
> Sent: Sunday, February 2, 2014 4:44 AM
> To: Kaz Kobara
> Cc: pari-users@pari.math.u-bordeaux.fr
> Subject: Re: Your help needed
> 
> On Thu, Jan 30, 2014 at 07:46:36AM +0900, Kaz Kobara wrote:
> > Dear Bill and all,
> >
> > > Not unless you know the factorisation of the order of the elliptic
> > > curve, or some similar useful information
> >
> > Thank you for this information.
> >
> > That's why the manual of ellorder()
> >
> http://pari.math.u-bordeaux.fr/dochtml/html/Functions_related_to_ell
> ip
> > tic_cu
> > rves.html
> > suggests to supply o of
> >
> > ? N = p+1-ellap(E,p); o = [N, factor(N)];
> >
> > This solved our problem. Thank you very much.
> 
> By curiosity, how did you compute factor(N) ?
> 
> Cheers,
> Bill.