Where is the spec of HashCash so that I can implement it in Java from scratch? I would like to implement HashCash in an efficient/fast/garbage-free way. Is there a spec to do so? How can someone go by implementing HashCash from scratch?
Not necessarily answering your question, but I found a HashCash implementation in Java already here: https://github.com/ryancwilliams/JHashCash Perhaps you can contribute or fork it?