Electronic payment systems can utilize digital tokens or electronic cash that is backed and stored in various ways. There are three main types of electronic cash based on when funds are debited from accounts - cash/debit, credit, and pre-paid. Electronic cash can be stored remotely on a computer's memory, smart cards, or other portable devices. Smart cards are another electronic payment method that can store sums of money and be used to pay small bills instantly. Credit card payments can be processed securely online through encryption or by using a third party verification service to confirm payments. Designing effective electronic payment systems requires addressing issues of privacy, security, usability and integration across different payment platforms and brokers.