(1) Except for cash, gold and silver, all money is digital. See
virtual currency and
cryptocurrency.
(2) With regard to e-commerce, PayPal and traditional credit cards are the primary form of digital money transfer. Web browsers and Web servers encrypt connections between user and online merchant (see
TLS). In the 2010s, mobile payment systems also emerged as a major form of digital money. See
Web payment service and
mobile payment service.
Pre-21st Century
This 1996 book was all about the methods for transferring money over the Internet just as the commercial Internet was becoming known to the world. The "crypto" in this book was about the cryptographic methods used to ensure trust and secure financial transactions for e-commerce.