First of all, SKALE Network supposes that all points lie in the affine plane, not projective. In this case, all z-coordinates are equal to zero. Also, if we have point in projective plane there is exactly one such point B on affine plane, that corresponds to A, and its coordinates .
Another important thing is that all coordinates are points and every coordinate has two other coordinates that are integers modulo
Now, lets follow the algorithm provided by libff and see, that the result is the same.
Here we can see what we got from libff algorithm. Now, let’s follow algorithm from SKALE’s code.
As we can see, the result of both algorithms is the same.