Over the Air Rekeying

Over the Air Rekeying (OTAR) is the common name for the method of changing or updating encryption keys in a two-way radio system over the radio channel (“over the air”). It is also referred to as Over-the-Air Transfer (OTAT), depending on the specific type and use of key being changed. Although the acronym refers specifically to radio transmission means, the technology is also employed via land line and cable.

Many of the newer NSA cryptographic systems that use a 128-bit electronic key, such as the ANDVT, KY-58, KG-84A/C, and KY-75, are capable of obtaining new or updated keys via the circuit they protect or other secure communications circuits. This process is known as over-the-air rekey (OTAR) or over-the-air transfer (OTAT). The use of OTAR/OTAT drastically reduces the distribution of physical keying material and the physical process of loading cryptographic devices with key tapes. A station may have nothing to do with actual physical key changeovers on a day-to-day basis. The electronic key would normally come from the Net Control Station (NCS). The added feature of OTAT is that the key can be extracted from an OTAT-capable cryptographic system using a fill device, such as the KYK-13 or KYX-15/KYX-15A. The key is then loaded into another cryptographic system as needed.