All of the Visa Direct APIs use Two-Way SSL (Mutual SSL) authentication and channel encryption, which requires you to provide a user name and password as well as install an X509 security certificate issued by Visa. Test credentials can be obtained online in your Project Dashboard for sandbox testing. Production credentials will be supplied to you as part of production on-boarding. Contact email@example.com 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.