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What are the implications of a curve having a non-integer co-factor for its generator point? Is that even possible?

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  • $\begingroup$ It depends on what you mean by "non-integer". If you have a rational like $\frac{2}{3}$, then that's possible ( if the inverse element exist, that's just a hidden inteder, because $3^{-1}$ is not a fraction but another integer). If you have a irrational number, then no. $\endgroup$ – tylo Feb 18 '14 at 10:53
  • $\begingroup$ tylo, very good point. I'd give you an upvote if you made an answer. $\endgroup$ – samoz Feb 24 '14 at 2:54
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The implications are that someone screwed up some calculation.
By Lagrange's theorem, the co-factor must be an integer.

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