Ripple is a payment system, currency exchange and remittance network by Ripple Labs. It is built upon a distributed, open source Internet protocol, consensus ledger and native currency called ripples (XRP). The Ripple network purports to enable “secure, instant and nearly free global financial transactions of any size with no chargebacks”. It supports tokens representing fiat currency (dollars, yen, etc.), cryptocurrency (bitcoin, litecoin, etc.), commodity or other unit of value (frequent flier miles, mobile minutes, etc.). At its core, Ripple is based around a shared, public database or ledger. In addition to balances, the ledger holds information about offers to buy or sell currencies and assets, creating the first distributed exchange. Participants in the network agree to changes in the ledger via a process called consensus which is reached every 2–5 seconds. The consensus process allows for payments, exchanges and remittance in a distributed process. The consensus model has been claimed to “not be safe in all circumstances” by Professor David Mazieres of Stanford’s secure computing group. On September 26, 2013, the Ripple reference server and client became free software, released under the terms of the ISC License. The current release of the client is version 0.2.48-3 and the server (known as rippled) is version 0.24.0. , Ripple is the second-largest cryptocurrency by market capitalization, after Bitcoin.