This commit changes the behavior of BitCurve.Add to be more inline
with btcd. It fixes two different bugs:
1) When adding a point at infinity to another point, the other point
should be returned. While this is undefined behavior, it is better
to be more inline with the go standard library.
Thus (0,0) + (a, b) = (a,b)
2) Adding the same point to itself produced the point at infinity.
This is incorrect, now doubleJacobian is used to correctly calculate it.
Thus (a,b) + (a,b) == 2* (a,b) and not (0,0) anymore.
The change also adds a differential fuzzer for Add, testing it against btcd.
Co-authored-by: Felix Lange <fjl@twurst.com>
Our original wrapper code had two parts. One taken from a third
party repository (who took it from upstream Go) licensed under
BSD-3. The second written by Jeff, Felix and Gustav, licensed
under LGPL. This made this package problematic to use from the
outside.
With the agreement of the original copyright holders, this commit
changes the license of the LGPL portions of the code to BSD-3:
---
I agree changing from LGPL to a BSD style license.
Jeff
---
Hey guys,
My preference would be to relicense to GNUBL, but I'm also OK with BSD.
Cheers,
Gustav
---
Felix Lange (fjl):
I would approve anything that makes our licensing less complicated
---
Marius van der Wijden
Péter Szilágyi
Felix Lange