IFF - Friend or Foe Identification Systems and Modes

Hardware

Radar (Receiver & Transmitter): Radar systems can be either internal to IFF or external systems integrated by manufacturers. Radar systems come in two types: primary and secondary. The primary type operates passively, only receiving signals without transmitting any. (Only receive) The secondary type operates actively and has the capability to transmit signals. (Both receiver and transmitter)

IFF Transponder (S-Mode Transponder): This hardware is a component installed on IFF systems. It responds to interrogation signals from radar with an encrypted reply indicating whether the target is friendly or hostile. The reply signal may contain identification information such as the device’s identity and location, depending on its sophistication. A single transponder is not required to support only one mode; it can have multiple security levels and transmit either military or civilian signals as needed. Consequently, it may incorporate various combinations of cryptographic modes.

Cryptographic Systems: These systems encrypt outgoing signals and decrypt incoming encrypted signals.

Software

Signal Processing: This function decodes incoming response signals, interrogates them, and classifies them as friendly or hostile.

IFF Communication

IFF Modes and Operating Principles

Modern IFF systems are capable of supporting multiple operation modes. Depending on the mission and operational scenario, the system can switch between modes. In necessary cases, it can transition to lower or higher security modes.

Mode-1: Provides limited security and is not encrypted. It is typically used by older systems in basic military operations. It includes both receiver and transmitter components and classifies incoming signals using a single method.

Mode-2: Involves the exchange of an identification code known only to military forces. It is not encrypted and is used in operations more critical than those employing Mode-1.

Mode-3A: Used in civil aviation for air traffic control. Communication is conducted via a code known as a “squawk code,” which corresponds to a specific aircraft or flight plan.

Mode-4: Encrypted military identification. The signal from the transponder is encrypted and can only be decrypted by authorized personnel. It employs two-way keying to resist spoofing. It is used in sensitive military operations and is currently employed by many military power worldwide.

Mode-5: Advanced encrypted identification. It is the most sophisticated mode currently available. It uses high-level encryption and is resistant to both jamming and spoofing. It is typically used on battle aircraft. NATO is open for use by NATO allies and countries participating in the F-35 JSF Program:

The following countries, which partner with NATO or are near allies, also use Mode-5 systems to ensure compatibility with NATO operations and secure identity verification: