What technology provides additional security for payment card transactions over HTTPS?

3-D Secure is a security protocol designed specifically to enhance security for online credit and debit card transactions, particularly when they are conducted over HTTPS. It acts as an additional layer of authentication during the payment process, helping to ensure that the individual making the transaction is the legitimate cardholder. When a consumer attempts to make a purchase online, this protocol prompts them to enter a password or a verification code that they would have set up with their bank, adding an extra step that enhances security.

The other options, while related to security in payment transactions, serve different purposes. Tokenization replaces sensitive payment information with non-sensitive equivalents (tokens), making it difficult for an attacker to misuse the data if intercepted; however, it does not provide the same immediate authentication layer as 3-D Secure. Payment gateways facilitate the transaction between the customer's bank and the merchant's bank but do not provide specific additional security measures on their own. Encryption secures data in transit; while essential, it operates at a level that does not include user authentication like 3-D Secure does. Thus, 3-D Secure is distinct in that it is specifically focused on secure authentication for online card transactions.