The SET Domain, or Secure Electronic Transaction Domain, is a protocol designed to ensure secure online credit card transactions. It was developed in the mid-1990s by a consortium of companies, including Visa and MasterCard, to protect sensitive information during electronic payments. The protocol uses encryption and digital signatures to authenticate parties involved in a transaction, ensuring that data remains confidential and secure. SET operates by creating a secure channel between the merchant, cardholder, and bank. When a customer makes a purchase, their payment information is encrypted and sent to the merchant, who then forwards it to the bank for authorization. This process helps prevent fraud and unauthorized access to financial data, making online shopping safer for consumers.