I'm not sure when they wrote this paper, but this is no longer true. There's some very nice official developer documentation up at: https://bitcoin.org/en/deve

I'm not sure when they wrote this paper, but this is no longer true. There's some very nice official developer documentation up at: https://bitcoin.org/en/developer-documentation https://bitcoin.org/en/developer-documentation Also, the Bitcoin Wiki itself is a fairly comprehensive source of documentation (and covers most of the information in the "official" documentation). It even includes an informal protocol specification[1]. It's been around for a very long time. That said, the information they're referring to is Bitcoin's Tor support (like recognizing OnionCat addresses). I don't think there is much documentation on this specific topic. However, Bitcoin is an open source project and I'm sure any related documentation contributions would be welcome. 1. https://en.bitcoin.it/wiki/Protocol_specification https://en.bitcoin.it/wiki/Protocol_specification