Post
Topic
Board Development & Technical Discussion
Re: Elliptic Curve Point Addition Question
by
Tanagi
on 26/01/2022, 05:04:24 UTC
If L = (y2 - y1) / (x2 - x1) what does 1 / (x2 - x1) mean?

It means that you take the result of x2 - x1 = xdiff, and then raise it to the (p-2)th power: xdiffp-2 mod p. (xdiffp-1 % p would be equal to 1, while xdiffp % p is simply xdiff) where p is the curve characteristic.

It's just a shorthand way of writing the above expression as division doesn't really exist in elliptic curves but modular inverses do.

I get this
Quote
It means that you take the result of x2 - x1 = xdiff

but I totally don't uderstand this
Quote
then raise it to the (p-2)th power: xdiffp-2 mod p. (xdiffp-1 % p would be equal to 1

I need this explained in the simplest possible terms please.

That's why I asked for a step by step breakdown (every step) would be much appreciated.