Fill device

In the 1950s and 1960s, systems such as the U.S. National Security Agency KW-26 and the Soviet Union's Fialka used punched cards for this purpose.

Newer NSA systems allow "over the air rekeying" (OTAR), but a master key often must still be loaded using a fill device.

Both employ the same U-229 6-pin connector type used for U.S. military audio handsets, with the DS-101 being the newer of the two serial fill protocols.

Besides encryption devices, systems that can require key fill include IFF, GPS and frequency hopping radios such as Have Quick and SINCGARS.

Common fill devices employed by NSA include: The older KYK-13,[6] KYX-15 and MX-10579 are limited to certain key types.