Replay Attack
A replay attack is the recording of a valid transmission on air and sending it again later exactly as it was. The attacker does not need to break the code; repeating the packet bit by bit is enough. It is the fundamental vulnerability of fixed code systems that send the same packet on every press.
An RF transmission travels in a shared medium; any receiver within range can listen to it. In a fixed code system the packet that is listened to stays valid forever, so when it is replayed the receiver counts it as a legitimate command.
- Rolling code: because the counter advances, the old packet is rejected; it is the most common countermeasure.
- Session authentication: establishing a fresh session on every connection invalidates recorded traffic.
- Encryption: it protects the confidentiality of the payload, but on its own it does not prevent replay; a fresh value or a counter is also needed.
In industrial remote control the risk is not only security but occupational safety: an unauthorised command means a suspended load or a moving hydraulic lever. For this reason, in lifting and hydraulic applications, protocols offering rolling code, an encrypted channel and mutual authentication are preferred over fixed code solutions.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety