What type of technical diagram best illustrates the secure communication path, including TLS/SSL handshakes and certificate validation, between a client application and an OTP validation service?

A Sequence Diagram best illustrates the secure communication path, including TLS/SSL handshakes and certificate validation, between a client application and an OTP validation service. A Sequence Diagram is a type of Unified Modeling Language (UML) interaction diagram that graphically represents the order of messages exchanged between objects or processes over time. It is particularly effective for depicting the precise chronological flow of interactions necessary for establishing a secure connection. The diagram uses vertical lifelines to represent the participating entities, such as the client application and the OTP validation service. Horizontal arrows between these lifelines represent messages exchanged, ordered chronologically from top to bottom. Activation boxes on lifelines indicate the period during which an object is performing an action. This visual structure directly supports the detailed depiction of the TLS/SSL handshake, which is a multi-step process for establishing a secure connection using the Transport Layer Security (TLS) or its predecessor Secure Sockets Layer (SSL) protocol. During this handshake, a Sequence Diagram explicitly shows the series of messages: for instance, the client application sends a "Client Hello" message to initiate communication; the OTP validation service responds with a "Server Hello" and its digital certificate. Certificate validation, the process by which the client application verifies the authenticity and trustworthiness of the server's digital certificate, is illustrated by the sequence showing the client receiving the certificate and then, critically, proceeding with subsequent handshake steps (like sending a "Client Key Exchange") only if the validation is successful. If validation fails, the diagram would show the connection being terminated instead of proceeding. This explicit chronological depiction of message exchanges and the dependency of subsequent steps on prior successful ones makes the Sequence Diagram unparalleled for clearly mapping out the secure communication path, the intricate steps of the TLS/SSL handshake, and the critical point of certificate validation.