Explicit-Formulas Database
Genus-1 curves over large-characteristic fields

Short Weierstrass curves

An elliptic curve in short Weierstrass form [database entry; Sage verification script; Sage output] has parameters a b and coordinates x y satisfying the following equations:
  y2=x3+a*x+b
Affine addition formulas: (x1,y1)+(x2,y2)=(x3,y3) where
  x3 = (y2-y1)2/(x2-x1)2-x1-x2
  y3 = (2*x1+x2)*(y2-y1)/(x2-x1)-(y2-y1)3/(x2-x1)3-y1
Affine doubling formulas: 2(x1,y1)=(x3,y3) where
  x3 = (3*x12+a)2/(2*y1)2-x1-x1
  y3 = (2*x1+x1)*(3*x12+a)/(2*y1)-(3*x12+a)3/(2*y1)3-y1
Affine negation formulas: -(x1,y1)=(x1,-y1).

The neutral element of the curve is the unique point at infinity, namely (0:1:0) in projective coordinates.

Representations for fast computations

Jacobian coordinates with a4=0 [more information] make the additional assumptions
  a=0
and represent x y as X Y Z satisfying the following equations:
  x=X/Z2
  y=Y/Z3

Jacobian coordinates with a4=-3 [more information] make the additional assumptions

  a=-3
and represent x y as X Y Z satisfying the following equations:
  x=X/Z2
  y=Y/Z3

Jacobian coordinates [more information] represent x y as X Y Z satisfying the following equations:

  x=X/Z2
  y=Y/Z3

Modified Jacobian coordinates [more information] represent x y as X Y Z T satisfying the following equations:

  x=X/Z2
  y=Y/Z3
  T=a*Z4

Projective coordinates with a4=-1 [more information] make the additional assumptions

  a=-1
and represent x y as X Y Z satisfying the following equations:
  x=X/Z
  y=Y/Z

Projective coordinates with a4=-3 [more information] make the additional assumptions

  a=-3
and represent x y as X Y Z satisfying the following equations:
  x=X/Z
  y=Y/Z

Projective coordinates [more information] represent x y as X Y Z satisfying the following equations:

  x=X/Z
  y=Y/Z

W12 coordinates with a6=0 [more information] make the additional assumptions

  b=0
and represent x y as X Y Z satisfying the following equations:
  x=X/Z
  y=Y/Z2

XYZZ coordinates with a4=-3 [more information] make the additional assumptions

  a=-3
and represent x y as X Y ZZ ZZZ satisfying the following equations:
  x=X/ZZ
  y=Y/ZZZ
  ZZ3=ZZZ2

XYZZ coordinates [more information] represent x y as X Y ZZ ZZZ satisfying the following equations:

  x=X/ZZ
  y=Y/ZZZ
  ZZ3=ZZZ2

XZ coordinates [more information] represent x y as X Z satisfying the following equations:

  x=X/Z