[curves] The great debate over point formats

Watson Ladd watsonbladd at gmail.com
Tue Jan 28 11:44:14 PST 2014

On Tue, Jan 28, 2014 at 11:41 AM, Michael Hamburg <mike at shiftleft.org> wrote:
> Do you mean the whole Edwards-x-coordinate, or just the sign?

Good catch: just the sign is probably the best choice.

> On Jan 28, 2014, at 11:40 AM, Watson Ladd <watsonbladd at gmail.com> wrote:
>> Right now there is a deep question: which point formats should be used
>> on Edwards curves? I am leaning towards Robert Ransoms suggestion of
>> specifying v coordinates on the isogenous Montgomery curve plus the x
>> coordinate of the Edwards curve. This enables a single implementation
>> to work for all protocols, if care is taken to discard the sign.
>> The one issue is several explicit formulas for isogenous Montgomery
>> ladders and conversion need to be worked out.
>> Sincerely,
>> Watson Ladd
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