Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.
Open Transactions is a solid, easy-to-use, financial crypto and digital cash library, including an API, server, and test client. It features anonymous numbered accounts, untraceable digital cash, triple-signed receipts, basket currencies, and signed XML contracts. It also supports cheques, invoices, payment plans, markets with trades, and other instruments. It uses OpenSSL and Lucre blinded tokens.
Moneychanger is a simple client GUI built on top of Open Transactions, a financial crypto library. Moneychanger can be used to create pseudonyms, issue currencies, open accounts, withdraw and deposit cash (untraceable digital cash), write and deposit cheques, trade on markets, and much, much more.
openHBCI is a C++ library for the German HomeBanking Computer Interface. It includes some tutorials for testing the library. Its current capabilities include complete key management on disc (RDH) and/or chip-card (DDV), the ability to perform single customer credit transfers, and the ability to get balance reports.
finic helps users manage their finances. It can be used on a local network (as a client-server system for many users) or on local computer (client only for one user), with separation of accounts, clauses, and customers. It can encrypt information and manage different users with different access rights. Reports can be generated as HTML, PDF, or XLS files or through an internal print preview system. An API is available for creating extensions.
JHBCI is JCA/JCE cryptographic service provider for Java. It is useful for building HBCI home banking applications (clients and servers). JHBCI implements all relevant "RDH" crypto algorithms for the German Homebanking Standard HBCI Version 2.2, such as DES, RSA, ISO9796-1:1991-Signature, and RIPEMD160-MessageDigest.