d. Transmission security key management.
(1) The current distribution scheme for TSK variables uses the same key for the entire corps.
If operations require units to travel into another corps area, the corps in place must transfer the TSK to
the transient unit. The signal staff officer or frequency manager in the transient unit coordinates with the
other corps' signal staff officer or frequency manager to obtain the correct TSK.
(a) The TSK is changed every 90 days. It must be physically loaded into the radio from a
fill device. The TSK variable may be transferred to the VINSON device over-the-air and then
physically loaded into the radio from the VINSON. Users must not transmit variables over nonsecure
radio links.
(b) Fill devices should be loaded with the current and the succeeding TSK variables for
quick transfer in case of compromise. The non-ICOM SINCGARS can be filled with only the current
and succeeding variables. The ICOM SINCGARS radio can hold up to six TSK variables. Maneuver
units fill the position with the TSK of the networks with which they are required to communicate. In
most cases, this is the corps common TSK for all six positions. Units located on the corps boundary
load the TSK of the adjacent unit into position 5 with the adjacent hopset
(c) Units that require communications with multiple echelons above corps (EAC) use the
following assignment for the six presets: Position 1 - local/division; position 2 - division/corps; position
3 - theater Army; position 4 - joint; position 5 - scratch location; and position 6 - TSK remote keying
variable. Positions 5 and 6 are used for remote keying of the TSKs over the radio link. The operators
follow the same procedure used to remote key VINSON COMSEC variables. Ground units that need to
communicate with tactical aircraft, such as air traffic control or forward air control units, use position 4
as the common TSK location.
(2) The COMSEC traffic encryption key (TEK) for VINSON and ICOM SINCGARS is
the same as the X encryption keys used by the KY-68 DSVT and KY-90 NRI device. The keys are
corps-common and distributed by the corps COMSEC manager through the MSE system. The key
encryption key (KEK) remains common only to the local network. The NCS capability to selectively
remote key individuals is retained to protect the network, should keyed equipment be captured. Remote
key procedures for the new systems are the same as those used with the VINSON devices.
e. Time management. The time reference all networks use is Zulu, or Greenwich Mean Time
(GMT). GMT is the basis for calculating time throughout the world. The network NCS or the net
timing station manages time. SINCGARS can send the NCS time reference to the network subscriber
over the radio link. This allows some leeway in time variation on initial loading. The subscriber who
cannot enter the network has the NCS send the correct time data. Any time the difference is between
four and 59 seconds, the subscriber
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