Ripple is a real-time gross settlement system (RTGS), currency exchange and remittance network by Ripple. Also called the Ripple Transaction Protocol (RTXP) or Ripple protocol, it is built upon a distributed open source Internet protocol, consensus ledger and native currency called XRP (ripples). Released in 2012, Ripple purports to enable "secure, instant and nearly free global financial transactions of any size with no chargebacks." It supports tokens representing fiat currency, cryptocurrency, commodity or any other unit of value such as frequent flier miles or mobile minutes. At its core, Ripple is based around a shared, public database or ledger, which uses a consensus process that allows for payments, exchanges and remittance in a distributed process. The security of the Ripple consensus algorithm was challenged by rivals in 2014, with Ripple defending the safety of the system. as of 2016, Ripple is the second-largest cryptocurrency by market capitalization, after bitcoin. Currently implemented by companies such as Fidor Bank, the Ripple protocol has been increasingly adopted by banks and payment networks as settlement infrastructure technology, with American Banker explaining that "from banks' perspective, distributed ledgers like the Ripple system have a number of advantages over cryptocurrencies like bitcoin," including price and security.