Which IFF mode provides a positive secure friend identification (classified)?

Which IFF mode provides a positive secure friend identification (classified)?

• A. Mode 4.
• B. Mode 3A.
• C. Mode 2.
• D. Mode C.

Answer: (A)

Positively identifying a friend in a secure way requires cryptographic authentication. Mode 4 is the encrypted IFF mode that uses a shared cryptographic key and a challenge–response exchange to prove an aircraft is a friend. The challenge keeps each identification fresh, and only an aircraft with the correct key can produce the valid response, giving authenticated identification that is resistant to spoofing. This makes the identification secure and, in many cases, classified. Other modes do not provide cryptographic authentication. A civilian Mode 3/A squawk code is simply a four-digit code used for ATC tracking and can be reproduced by others; Mode 2 uses unit identification codes without encryption; Mode C only reports altitude. So Mode 4 is the one that provides the positive secure friend identification.

Positively identifying a friend in a secure way requires cryptographic authentication. Mode 4 is the encrypted IFF mode that uses a shared cryptographic key and a challenge–response exchange to prove an aircraft is a friend. The challenge keeps each identification fresh, and only an aircraft with the correct key can produce the valid response, giving authenticated identification that is resistant to spoofing. This makes the identification secure and, in many cases, classified.

Other modes do not provide cryptographic authentication. A civilian Mode 3/A squawk code is simply a four-digit code used for ATC tracking and can be reproduced by others; Mode 2 uses unit identification codes without encryption; Mode C only reports altitude. So Mode 4 is the one that provides the positive secure friend identification.