Paper 2021/383
GLV+HWCD for 2y^2=x^3+x/GF(8^91+5)
Daniel R. L. Brown
Abstract
This report considers combining three wellknown optimization methods for elliptic curve scalar multiplication: GallantLambertVanstone (GLV) for complex multiplication endomorphisms $[i]$ and $[i+1]$; 3bit fixed windows (signed base 8); and HisilWongCarterDawson (HWCD) curve arithmetic for twisted Edwards curves. An $x$only DiffieHellman scalar multiplication for curve $2y^2=x^3+x$ over field size $8^{91}+5$ has arithmetic cost $947\textbf{M} + 1086\textbf{S}$, where $\textbf{M}$ is a field multiplication and $\textbf{S}$ is a field squaring. This is approximately $(3.55\textbf{M} + 4.07\textbf{S})$/bit, with $1\textbf{S}$/bit for input decompression and $1\textbf{S}$/bit for output normalization. Optimizing speed by allowing uncompressed input points leads to an estimate $(3.38\textbf{M}+2.95\textbf{S})$/bit. To mitigate some sidechannel attacks, the secret scalar is only used to copy curve points from one array to another: the field operations used are fixed and independent of the secret scalar. The method is likely vulnerable to cachetiming attacks, nonetheless.
Metadata
 Available format(s)
 Category
 Implementation
 Publication info
 Preprint. MINOR revision.
 Keywords
 elliptic curve cryptosystem
 Contact author(s)
 danibrown @ blackberry com
 History
 20210327: received
 Short URL
 https://ia.cr/2021/383
 License

CC BY
BibTeX
@misc{cryptoeprint:2021/383, author = {Daniel R. L. Brown}, title = {GLV+HWCD for 2y^2=x^3+x/GF(8^91+5)}, howpublished = {Cryptology ePrint Archive, Paper 2021/383}, year = {2021}, note = {\url{https://eprint.iacr.org/2021/383}}, url = {https://eprint.iacr.org/2021/383} }