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 [Ler96] 
R. Lercier. Computing isogenies in GF(2^{n}).
In H. Cohen, editor, Algorithmic Number Theory:
Second International Symposium, ANTSII Talence, France, May 1823, 1996
Proceedings, volume 1122 of Lecture Notes in Computer Science, pages
197212. Springer Berlin / Heidelberg, May 1996.
Contrary to what happens over prime fields of large
characteristic, the main cost when counting the number of
points of an elliptic curve E over GF(2^{n}) is the
computation of isogenies of prime degree l. The best
method so far is due to Couveignes and needs asymptotically
O(l^{3}) field operations. We outline in this article some
nice properties satisfied by these isogenies and show how we
can get from them a new algorithm that seems to perform
better in practice than Couveignes's though of the same
complexity. On a representative problem, we gain a speedup
of 5 for the whole
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