Which of these must be protected under the crypto security component of communications security (COMSEC)?

In the context of communications security (COMSEC), the component that must be protected is the keys used to scramble or change a message transmission. These cryptographic keys are critical because they ensure the confidentiality and integrity of the transmitted information. If these keys are compromised, an unauthorized party could decrypt and access sensitive communications. Therefore, protecting cryptographic keys is a foundational aspect of maintaining secure communication channels.

The other options, while important aspects of communication equipment and processes, do not have the same level of indispensability when it comes to the specific protections mandated by COMSEC. Communication devices are physical tools that can be secured through various means, access codes relate to user-specific permissions but do not directly encrypt the information, and message recipients, while important for operational understanding, do not require the same level of cryptographic protection as the keys used in encryption processes.