Computing 2-isogenies between Kummer lines
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Abstract
We use theta groups to study $2$-isogenies between Kummer lines, with a particular focus on the Montgomery model. This allows us to recover known formulas, along with more efficient forms for translated isogenies, which require only $2S+2m_0$ for evaluation. We leverage these translated isogenies to build a hybrid ladder for scalar multiplication on Montgomery curves with rational $2$-torsion, which cost $3M+6S+2m_0$ per bit, compared to $5M+4S+1m_0$ for the standard Montgomery ladder.
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How to cite
Damien Robert and Nicolas Sarkis, Computing 2-isogenies between Kummer lines. IACR Communications in Cryptology, vol. 1, no. 1, Apr 09, 2024, doi: 10.62056/abvua69p1.
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This work is licensed under a Creative Commons Attribution (CC BY) license.