Linking protection for HF radio automatic link establishment

摘要

A proposed standard has been developed by the US FederalnGovernment to provide a degree of security to high-frequency (HF) radiosnimplementing the automatic link establishment (ALE) protocol. As withnall automated communication systems, some form of authentication isnneeded to validate the identity of the caller. The protection mechanismnfor the ALE protocol, termed linking protection (LP), provides securitynagainst ALE vulnerabilities such as unauthorized net entry and denial ofnaccess to legitimate users, and also protects the address and orderwirenmessage information. Encryption of the ALE transmissions is based onntime-varying information so that previous messages that are played backnat a later time appear unintelligible to the receiver. The securitynoffered by LP is directly related to the type of cryptographic algorithmnand the length of the protection interval. The transparency of LP to thenALE protocol provides various system benefits such as establishing anlink in the same amount of time as a nonprotected station and allowing anscanning receiver to acquire synchronization at any point in antransmission