Visa Travel Notification API uses mutual SSL authentication and channel encryption, which requires that you obtain a user ID and password as well as install a PKI certificate issued by Visa. You can obtain the test credentials online in the Project Console for sandbox testing. Production credentials will be supplied to you as part of the production on-boarding process. Contact firstname.lastname@example.org for more information or to begin the production on-boarding process.
As one of the security protocols, Visa Developer sandbox secures its connections with clients by means of Two-Way SSL (Mutual Authentication) method. Refer to the link below to quickly learn about how to get credentials to start building with Two-Way SSL.
Visit the Two-way SSL Guide to learn more.