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Faster halvings in genus 2. (English) Zbl 1256.94044

Avanzi, Roberto Maria (ed.) et al., Selected areas in cryptography. 15th international workshop, SAC 2008, Sackville, New Brunswick, Canada, August 14–15. Revised selected papers. Berlin: Springer (ISBN 978-3-642-04158-7/pbk). Lecture Notes in Computer Science 5381, 1-17 (2009).
Summary: We study divisor class halving for hyperelliptic curves of genus 2 over binary fields. We present explicit halving formulas for the most interesting curves (from a cryptographic perspective), as well as all other curves whose group order is not divisible by 4. Each type of curve is characterized by the degree and factorization form of the polynomial \(h(x)\) in the curve equation. For each of these curves, we provide explicit halving formulæ for all possible divisor classes, and not only the most frequent case where the degree of the first polynomial in the Mumford representation is 2. In the optimal performance case, where \(h(x) = x\), we also improve on the state-of-the-art and when \(h(x)\) is irreducible of degree 2, we achieve significant savings over both the doubling as well as the previously fastest halving formulas.
For the entire collection see [Zbl 1173.94003].

MSC:

94A60 Cryptography
11G20 Curves over finite and local fields
14G50 Applications to coding theory and cryptography of arithmetic geometry
Full Text: DOI

References:

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