On 6/13/07, Joseph Hufnagle <> wrote:
> Dear Sir,
>       Is it possible to find the order of a point of an elliptic curve over
> a finite field using SAGE? I have been unable to find anything in the
> tutorial or reference.
>       Thank You,

Is the finite field GF(p) or GF(p^n) with n >= 2.  If the former,

sage: e = EllipticCurve(GF(11),range(5))
sage: P = e([4,2])
sage: P.order()
6

In the latter case, also use the order method:
sage: e = EllipticCurve(GF(11^2,'a'),range(5))
sage: P = e([4,2])
sage: P.order()
WARNING -- using naive point order finding over finite field!
6

*However* this is very stupidly slow.  Fortunately, Martin Albrecht (a
sage developer)
did send me a patch a few days ago that implements a very fast algorithm for
computing the order of a point -- unfortunately, it's not in the
current version of SAGE,
though it will be in the next version, which will be released within a week.
(I can also make the patch available to you if you need it.)

William

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