bcoin VS libtorsion

You can just submit your changes to the Bitcoin core repo https://github.com/bitcoin/bitcoin or you can fork it and create your own version. You can even just use/change one of the alternative implementations: https://github.com/bcoin-org/bcoin

I'm not sure what you mean by "truly separate", but our hot wallets are indeed separate wallets, both running on top on bcoin.io

bcoin

My first bitcoin reimplementation was written in node.js and called bcoin[1]. So this is my second time reimplementing the bitcoin protocol, albeit in a very different language.

Bcoin was frequently used as a reference along with bitcoin core v0.8.0-v0.11.0 when I felt like double checking consensus functions (among other things).

As an aside, I personally think bitcoin core v0.8.0 is the best version of core if you want to learn bitcoin from it. It's a lot more straightforward than later versions. I personally don't enjoy reading any version beyond v0.11.0.

This is also the reason mako doesn't support taproot yet. That code is very new and isn't present in upstream bcoin. I could try to implement it from the BIPs alone, but I won't know what intricacies are present in the actual bitcoin core code until I actually read it.

[1] https://github.com/bcoin-org/bcoin

Hey guys, Is there a way to run a bitcoin-core program (like https://github.com/bcoin-org/bcoin) without downloading the blockchain?

Most of the crypto is from my more general crypto library libtorsion: https://github.com/bcoin-org/libtorsion

I originally wanted to vendor my libtorsion code and link to it, but it felt clunky since libtorsion pulls in a ton of crypto that bitcoin doesn't need. Also, since I was focusing on just a few algorithms, it gave me the opportunity to optimize a lot of them (in particular, the ECC backend was optimized for secp256k1 whereas in libtorsion it supports all kinds of curves).

Because of all of this, there's probably some leftover comments. That comment isn't true anymore. rand.c is definitely used internally for libmako, just not libtorsion.

edit: fixed link.

The 2-by-1 and 3-by-2 division functions described in the paper result in a very measurable speedup in my code. I think you're confusing those with the reciprocal calculation itself (which can be computed with a lookup table). I agree that part doesn't really lend itself to any significant performance benefit and is probably better calculated with a single hardware division instead.

I feel it necessary to point out that the 3-by-2 division actually has multiple benefits which are easy to miss:

1. The quotient loop can be skipped as I mentioned.

2. The "Add back" step is less likely to be triggered.

3. Since a 2-word remainder is computed with the division, you can skip 2 iterations on the multiply+subtract step.

My reimplementation of GMP documents both the 2-by-1 and 3-by-2 divisions pretty thoroughly[1][2].

[1] https://github.com/bcoin-org/libtorsion/blob/master/src/mpi....

[2] https://github.com/bcoin-org/libtorsion/blob/master/src/mpi....