New answers tagged secp256k1
0
As other's have said, the essential point is the algebraic definition for additive inverses in elliptic arithemetic.
-(x,y)=(x,-y)
But if it helps, there are also some nice geometric illustrations like this one from Vitalik Buterin's Exploring Elliptic Curve Pairings:
Suppose R = (x,y). Since the elliptic curve is symmetric with respect to the x-axis, we ...
0
Here is the sample of code for subtraction of two points.
# -*- coding: utf-8 -*-
def OnCurve(x,y): # Check if the point is on the curve
A = (y*y)%P
B = (x*x*x)%P
C = False
if A == (B + 7):
C = True
return C
def ECadd(xp,yp,xq,yq): # EC point addition
m = ((yq-yp) * modinv(xq-xp,P))%P
xr = (m*m-xp-xq)%P
yr = (m*(xp-...
4
You can negate a point (x, y) by simply changing it to (x, −y).
The document that defines ECDSA reminds us of this fact:
https://www.secg.org/sec1-v2.pdf
Here's a screenshot:
So once you have negated one of your points, just add it to the other one, and you have achieved subtraction.
Top 50 recent answers are included
