Cryptology ePrint Archive: Report 2017/669

Speeding up Elliptic Curve Scalar Multiplication without Precomputation

Kwang Ho Kim and Junyop Choe and Song Yun Kim and Namsu Kim and Sekung Hong

Abstract: This paper presents a series of Montgomery scalar multiplication algorithms on general short Weierstrass curves over odd characteristic fields, which need only 12 field multiplications plus 12 ~ 20 field additions per scalar bit using 8 ~ 10 field registers, thus significantly outperform the binary NAF method on average. Over binary fields, the Montgomery scalar multiplication algorithm which was presented at the first CHES workshop by L´opez and Dahab has been a favorite of ECC implementors, due to its nice properties such as high efficiency outperforming the binary NAF, natural SPA-resistance, generality coping with all ordinary curves and implementation easiness. Over odd characteristic fields, the new scalar multiplication algorithms are the first ones featuring all these properties. Building-blocks of our contribution are new efficient differential addition-and-doubling formulae and a novel conception of on-the-fly adaptive coordinates which softly represent points occurring during a scalar multiplication not only in accordance with the basepoint but also bits of the given scalar. Importantly, the new algorithms are equipped with built-in countermeasures against known side-channel attacks, while it is shown that previous Montgomery ladder algorithms with the randomized addressing countermeasure fail to thwart attacks exploiting address-dependent leakage.

Category / Keywords: Elliptic curve cryptography • Scalar multiplication • Montgomery ladder • Countermeasures against SCA

Date: received 25 Jun 2017, last revised 5 Jul 2017

Contact author: pgitech namsukim at aliyun com

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Note: I have changed authors list.

Version: 20170706:043818 (All versions of this report)

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