Open Transactions is free open source financial software, providing API libraries for several programming languages including script languages as well as compiled languages.
It provides an array of fundamental financial cryptography functions including chaumian blinding, triple signed receipts, transaction history destruction, secure connections, signed transactions and receipts and so on. Probably the best current source of detailed information is at FellowTraveler's GitHub site, https://github.com/FellowTraveler
Open Transactions was adopted by the Galactic Milieu when open source software suitable for implementing banking, stock exchanges, commodity exchanges and so on was searched for. It is hoped that Open Transactions will eventually permit each Bank and Stock Exchange built in an city of a Galactic Milieu planet to actually function instead of merely being an abstract bonus item for the city within the Freeciv rules as governed by the Galactic Ruleset.
So far only one test Open Transactions server for the Galactic Milieu is in operation, the Digitalis server run by Digitalis Data Services of Halifax, Nova Scotia (in Canada on the planet known as Earth). The contract for the Digitalis Open Transactions server can be found online in the downloads area of the Galactic Milieu project on Sourceforge (http://sourceforge.net/projects/galacticmilieu/files/) as the file named DigitalisOTserver.otc … The contract contains the hostname and port information used by Open Transactions clients to connect to the server.