The confidentiality of data regarding your credit card payments are fully guaranteed. Payments made through Visa / Mastercard performed by protocol SSL encrypted secure servers.
What is a secure server?
A secure server guarantees the privacy of the data transmitted by the networks. This privacy is achieved by SSL 128-bit encryption. Security is the result of the communication between a browser and a server under SSL protocol with the same protocol. Any version of "browser" Netscape Navigator and Microsoft Internet Explorer supports this protocol.
How do I know that a server is secure?
For the key that appears at the bottom left of the browser, or the padlock that appears at the bottom right of your browser if you use Microsoft Explorer. You can also see that the URL changes: no longer begins with http but https.