IsogenyMap defines an isogeny between curves of
form Phi(x, y) := (a(x), b(x)*y). The xcoordinate of the codomain point only depends on thex-coordinate of the domain point, and the y-coordinate of the codomain point is a multiple of the y-coordinate of the domain point. The multiplier depends on the x`-coordinate of the domain point.
All isogeny maps of curves of short Weierstrass form can be written in this way. See
[[Ga18]]. Theorem 9.7.5 for details.
Trait defining the necessary parameters for the WB hash-to-curve method
for the curves of Weierstrass form of:
of y^2 = x^3 + a*x + b where b != 0 but a can be zero like BLS-381 curve.
From [[WB2019]]