machines using mobile payments. PayPal launched its USD-denominated service in 1998. In 2009, bitcoin was launched, which marked the start of decentralized blockchain-based digital currencies with no central server, and no tangible assets held in reserve. Also known as cryptocurrencies, blockchain-based digital currencies proved resistant to attempt by government to regulate them, because there was no central organization or person with the power to turn them off. Origins of digital currencies date back to the 1990s Dot-com bubble. Another known digital currency service was Liberty Reserve, founded in 2006; it lets users convert dollars or euros to Liberty Reserve Dollars or Euros, and exchange them freely with one another at a 1% fee. Several digital currency operations were reputed to be used for Ponzi schemes and money laundering, and were prosecuted by the U.S. government for operating without MSB licenses. Q coins or QQ coins, were used as a type of commodity-based digital currency on Tencent QQ's messaging platform and emerged in early 2005. Q coins were so effective in China that they were said to have had a destabilizing effect on the Chinese Yuan currency due to speculation. Recent interest in cryptocurrencies has prompted renewed interest in digital currencies, with bitcoin, introduced in 2008, becoming the most widely used and accepted digital currency. Sub-types of digital currency and comparisons Digital currency as a specific type and as a meta-group name Digital Currency is a term that refers to a specific type of electronic currency with specific properties. Digital Currency is also a term used to include the meta-group of sub-types of digital currency, the specific meaning can only be determined within the specific legal or contextual case. Legally and technically, there already are a myriad of legal definitions of digital currency and the many digital currency sub-types. Combining different possible properties, there exists an extensive number of implementations creating many and numerous sub-types of Digital Currency. Many governmental jurisdictions have implemented their own unique definition for digital currency, virtual currency, cryptocurrency, e-money, network money, e-cash, and other types of digital currency. Within any specific government jurisdiction, different agencies and regulators define different and often conflicting meanings for the different types of digital currency based on the specific properties of a specific currency type or sub-type. Digital versus virtual currency A virtual currency has been defined in 2012 by the European Central Bank as "a type of unregulated, digital money,