btcd

Actively used alternative implementations: https://github.com/btcsuite/btcd https://bitcoin-s.org/ https://bcoin.io/ https://bitcore.io/ https://bitcoindevkit.org/

btcd is an existing implementation in go https://github.com/btcsuite/btcd

It would be disingenuous to claim that the Bitcoin protocol is only defined by the consensus layer. Then, if you require P2P protocol compatibility, I would say this issue shows that nobody really cares about alternate implementations: https://github.com/btcsuite/btcd/issues/1661 When Btcd was first released, it was pretty capable, and had lots of development. But it has fallen behind, which makes sense. Why would anybody take the risk of trusting that an alternate implementation when it doesn't decide what bitcoin is, in the end? You may have to patch bitcoind a bit to get your desired interface, but that is much less work than maintaining a full P2P and consensus layer. It is also dangerous to use you a non-standard crypto library. Check this vulnerability, which was caused by LND relying on the btcd project's library: https://lists.lin

Someone else linked it below: https://github.com/bitcoin/bitcoin/blob/e071a3f6c06f41068ad1... Equivalent check in btcd, an alternative Bitcoin implementation: https://github.com/btcsuite/btcd/blob/991d32e72fe84d5fbf9c47...

For your second, link, the PoC example there by passes the regular strict signature encoding checks. These are on by default, with some being policy, and some being consensus. As a result, this won't be hit in practice by regular nodes, but may be hit by developers using the library for other purposes: https://github.com/btcsuite/btcd/issues/1287#issuecomment-42...

I spend a lot of time looking for bugs in cryptocurrency code. In spite of this finding, I'd say that Bitcoin Core is among the safest cryptocurrency applications. The average random C/C++ open source project suffers from far more potential issues, for example [1]. Related, here's an unfixed btcd (Go Bitcoin client) DoS [2]. [1] https://bugs.chromium.org/p/oss-fuzz/issues/list?q=imagemagi... [2] https://github.com/btcsuite/btcd/issues/1287

Humble suggestion / shameless plug: try using Sourcegraph to read through some of the excellent codebases mentioned in other posts. This is basically our prime use case (I'm one of the creators): reading through and understanding code structure with jump-to-def / find-refs / symbol search in your browser. I'd suggest starting with the main function and tracing through the static structure of the codebase from there: https://sourcegraph.com/github.com/golang/go/-/blob/src/net/... https://sourcegraph.com/github.com/mholt/caddy@master/-/blob... https://sourcegraph.com/github.com/btcsuite/btcd@master/-/bl... https://sourcegraph.com/github.com/camlistore/camlistore@mas... https://sourcegraph.com/github.com/boltdb/bolt@master/-/blob... https://sourcegraph.com/github.com/go-kit/kit/-/blob/example...

https://github.com/btcsuite/btcd Learned a lot from reading this code

I worked this summer as an intern at Conformal Systems where we developed a more sophisticated version of this, essentially a simulator [1] where random transactions between wallets can happen. The main reason for this was to stress-test btcd [2], the full-node bitcoin client that is developed by Conformal. Overall it was a great experience working with Go and bitcoin. [1] https://github.com/conformal/btcsim [2] https://github.com/conformal/btcd

Here's a Go rewrite that excels in safety over it's C++ original especially when working with the raw bitcoin protocol for multi sig transactions https://github.com/conformal/btcd