### On isogeny classes of Edwards curves over finite fields

##### Abstract

We count the number of isogeny classes of Edwards curves over finite fields, answering a question recently posed by Rezaeian and Shparlinski. We also show that each isogeny class contains a {\em complete} Edwards curve, and that an Edwards curve is isogenous to an {\em original} Edwards curve over $\F_q$ if and only if its group order is divisible by $8$ if $q \equiv -1 \pmod{4}$, and $16$ if $q \equiv 1 \pmod{4}$. Furthermore, we give formulae for the proportion of $d \in \F_q \setminus \{0,1\}$ for which the Edwards curve $E_d$ is complete or original, relative to the total number of $d$ in each isogeny class.

Available format(s)
Category
Public-key cryptography
Publication info
Published elsewhere. preprint
Keywords
number theory
Contact author(s)
rgranger @ computing dcu ie
History
Short URL
https://ia.cr/2011/135

CC BY

BibTeX

@misc{cryptoeprint:2011/135,
author = {Omran Ahmadi and Robert Granger},
title = {On isogeny classes of Edwards curves over finite fields},
howpublished = {Cryptology ePrint Archive, Paper 2011/135},
year = {2011},
note = {\url{https://eprint.iacr.org/2011/135}},
url = {https://eprint.iacr.org/2011/135}
}
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