Open Banking APIs - What Is Mutual TLS?

TLS is the secure transport protocol that underlies HTTPS and we use it all the time. It's how websites authenticate themselves to us using a web browser. The TLS also provides an option for the client to provide a certificate during the handshake and prove possession of the associated private key. So it's typically then used in a manner to authenticate the client but is also a proof of possession mechanism for a public private key pair as well.