<P> There are companies that enable financial transactions to take place over the internet, such as PayPal . Many of the mediaries permit consumers to establish an account quickly, and to transfer funds into their on - line accounts from a traditional bank account (typically via ACH transactions), and vice versa, after verification of the consumer's identity and authority to access such bank accounts . Also, the larger mediaries further allow transactions to and from credit card accounts, although such credit card transactions are usually assessed a fee (either to the recipient or the sender) to recoup the transaction fees charged to the mediary . </P> <P> The speed and simplicity with which cyber-mediary accounts can be established and used have contributed to their widespread use, although the risk of abuse, theft and other problems--with disgruntled users frequently accusing the mediaries themselves of wrongful behavior is associated with them . </P> <P> Credit cards constitute a popular method of online payment but can be expensive for the merchant to accept because of transaction fees primarily . Debit cards constitute an excellent alternative with similar security but usually much cheaper charges . Besides card - based payments, alternative payment methods have emerged and sometimes even claimed market leadership . Wallets like PayPal and Alipay are playing major roles in the ecosystem . Bitcoin payment processors are a cheaper alternative for accepting payments online which also offer better protection from fraud . </P> <P> This is a system that does not involve any sort of physical card . It is used by customers who have accounts enabled with Internet banking . Instead of entering card details on the purchaser's site, in this system the payment gateway allows one to specify which bank they wish to pay from . Then the user is redirected to the bank's website, where one can authenticate oneself and then approve the payment . Typically there will also be some form of two - factor authentication . Some services, like Trustly, let merchants embed its iframe on their website so consumers can pay without being redirected away from the original site . </P>

Elucidate the security schemes in electronic payment systems