There are currently over 2,000 crypto assets like Bitcoin that can be exchanged for goods and services in many countries anonymously, instantaneously, and at any time. These emerging forms of private sector money, or crypto currencies, provide their own units of account and are based on ledger technology such as blockchain which makes the falsification of transaction data difficult. Unlike cash, transactions using crypto assets are also technically traceable and a positive or negative interest rate can be charged, potentially improving the effectiveness of monetary policy.