Abstract
The necessary and sufficient conditions for the parameters of the curve in the canonical form with two points of order 4 are found. Two lemmas about the properties of quadratic residues are proved, using the Gauss scheme for quadratic residues and non-residues. Based on this lemmas, the exact formulas are derived for the number of elliptic curves with non-zero parameters a and b and two points of order 4 that are isomorphic to Edwards curves over the prime field. It is proved that for large fields the share of such curves is close to 1/4.
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References
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Translated from Kibernetika i Sistemnyi Analiz, No. 2, March–April, 2015, pp. 3–12.
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Bessalov, A.V., Kovalchuk, L.V. Exact Number of Elliptic Curves in the Canonical Form, Which are Isomorphic to Edwards Curves Over Prime Field. Cybern Syst Anal 51, 165–172 (2015). https://doi.org/10.1007/s10559-015-9709-x
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DOI: https://doi.org/10.1007/s10559-015-9709-x
Keywords
- canonical elliptic curve
- Edwards curve
- twist curve
- curve parameters
- isomorphism
- quadratic residue
- quadratic non-residue