On the Wikipedia page of ECDSA, it is stated in step 6 of the verification algorithm that
If (x1,y1)=O then the signature is invalid.
In X9.62, it is also stated that
If u1G + u2Q is the point at
infinity, then reject the signature.
However, I cannot find explicit checking for this condition in multiple open-source libraries.
python-ecdsa for example:
xy = u1 * G + u2 * self.point v = xy.x() % n return v == r
Is there any implicit checking that I missed?
And is there any possible attacking against this, if such a verification was missed?