Wow! Impressive how fast you did this!
Thanks, but it is mostly the fact that the bouncy castle library has an EC point library built in.
Also, the formula just "worked". I had expected an hour or two of debugging at least.
- I suppose that addition can be sped up in bounty castle because parameter 'A' is zero for the BC curve.
Dunno. It looks like addition doesn't actually depend on the curve parameters, weirdly.
It should, but that's probably taken care of in the addition part of the code. I don't think you can do much better than what you've done.
article proposes some additional improvements on the naive double-and-add but I've just skimmed the paper so not sure if it's worth the effort.