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Communications security is the discipline of preventing unauthorized interceptors from accessing telecommunications in an intelligible form, while still delivering content to the intended recipients. In the United States Department of Defense culture, it is often referred to by the portmanteau COMSEC. The field includes cryptosecurity, transmission security, emission security, traffic-flow security. and physical security of COMSEC equipment.



COMSEC is used to protect both classified and unclassified traffic on military communication networks, including voice, video, and data. It is used for both analog and digital applications, and both wired and wireless links.

Secure voice over internet protocol (SVOIP) has become the defacto standard for securing voice communication, replacing the need for STU-X and STE equipment in much of the U.S. Department of Defense. USCENTCOM moved entirely to SVOIP in 2008.[1]


  • Cryptosecurity: The component of communications security that results from the provision of technically sound cryptosystems and their proper use. This includes ensuring message confidentiality and authenticity.
  • Emission security (EMSEC): Protection resulting from all measures taken to deny unauthorized persons information of value which might be derived from intercept and analysis of compromising emanations from crypto-equipment, automated information systems (computers), and telecommunications systems.
  • Physical security: The component of communications security that results from all physical measures necessary to safeguard classified equipment, material, and documents from access thereto or observation thereof by unauthorized persons.
  • Traffic-flow security: Measures that conceal the presence and properties of valid messages on a network. It includes the protection resulting from features, inherent in some cryptoequipment, that conceal the presence of valid messages on a communications circuit, normally achieved by causing the circuit to appear busy at all times.
  • Transmission security (TRANSEC): The component of communications security that results from the application of measures designed to protect transmissions from interception and exploitation by means other than cryptanalysis (e.g. frequency hopping and spread spectrum).

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