A cryptocurrency is a digital or virtual currency designed to work as a medium of exchange. It uses cryptography to secure and verify transactions as well as to control the creation of new units of a particular cryptocurrency. Essentially cryptocurrencies are limited entries in a database that no one can change unless specific conditions are fulfilled. The countries where bitcoin is never legally acceptable as a substitute for a country's tender are The United States of America, Canada, The European Union, Australia, Russia, Vietnam, Bolivia, Columbia and Ecuador.