Which protocol secures the REST API communication channel?

HTTPS (Hypertext Transfer Protocol Secure) is the correct choice because it encrypts the communication between a client and a server using SSL/TLS, ensuring the confidentiality and integrity of data exchanged over a REST API. This prevents eavesdropping and tampering. HTTP is insecure as it transmits data in plain text. SSH (Secure Shell) is primarily used for secure remote access to network devices and executing commands, not for securing REST API communication channels directly. TCP (Transmission Control Protocol) is a fundamental transport layer protocol that provides reliable, ordered, and error-checked delivery of a stream of octets between applications, but it does not inherently provide encryption for application-layer protocols like REST APIs.