This is a prototype of Spacemint (Spacecoin), which is described in more detail at https://eprint.iacr.org/2015/528.pdf (Cryptocurrency) https://eprint.iacr.org/2013/796.pdf (Proof-of-space; PoS). This README explains some implementation details.
The proof-of-space part of this is being re-implemented, and a version of it is already moved to https://github.com/kwonalbert/pospace.
##Structure of the graph
For proof-of-space, the graphs are generated once, and are read only for rest of its life-time. Moreover, the only operations we need to do are parent look up and hash lookups. We therefore pick a simple graph representation in the file system, and avoid using a more sophisticated solution like graph database.
The graphs used in the prototype from PTC76 (Paul, Tarjan and Celoni). The graph is recursively generated. Each node is just a hash, and you can directly access the node by reading hash at id * size of hash. The code is written in a way to minimize the HDD head movement, at the cost of some minor compute during initialization.
##Directory Structure block/ Cryptocurrency block files
pos/ Proof-of-Space implementation
util/ Various utilities used by block and pos