2. Scientific discussion
2.6. Clinical aspects
2.6.6. Discussion on clinical efficacy
AK rekeying operations require the receiving radio be loaded with the same KEK used to send the rekey from the sender’s NCD or DTD. The KEK must be distributed and loaded prior to using AK operations. After each AK OTAR operation, the KEK loaded in radio is updated automatically by the rekey process. The sending operator must then update the KEK in the DTD or NCD after confirmation of successful OTAR at the receiving radios. For variable update, refer to Paragraph 3.22.5. For CRYPTO TYPES VINSON and ANDVT, follow the procedure in Paragraph 3.22.1.1. For CRYPTO TYPE KG84, follow the procedure in Paragraph 3.22.1.2.
3.22.1.1 TX AK Using ANDVT or VINSON
For TX AK operations the radio presets must be correctly set up, depending on COMSEC type. Certain COMSEC types require the correct key type and modem as follows:
•
TX AK ANDVT-HF - ANDVT-HF crypto key - ANDVT-HF modem•
TX AK ANDVT-BD - ANDVT-BD crypto key - serial modem•
TX AK VINSON - VINSON crypto key - no modem requiredPerform the following procedure for TX AK:
a. Determine TEK that is to be transmitted by AK OTAR. Load this TEK into the AN/PRC-150(C) to have available for communications checks after OTAR with receiving stations.
b. Notify receiving stations to prepare for AK OTAR. Direct them to use cooperative or noncooperative method. Refer to Paragraph 3.22.1.3.1 and Paragraph 3.22.1.3.2. Verify the CRYPTO TYPE is either VINSON or ANDVT. Additionally, instruct them not to transmit again until they hear a
communications check. If using cooperative method, tell receiving station to receive new key and store in an unused storage position.
c. Rotate the function switch to RV.
d. Select TRANSMIT AK; press [ENT]. WAIT - CONFIGURING FOR TX AK displays.
CONNECT NCD AND INITIATE AK displays.
e. Connect KYX-15 (NCD) or AN/CYZ-10 (DTD) fill device to J18 FILL connector. INITIATE AK displays on KDU.
f. On the fill device, select AK, the TEK to be transmitted, and the KEK used by the receiving stations.
Consult NCD or DTD operations manual if necessary.
g. Initiate the AK from the fill device. TX AK IN PROGRESS displays on the KDU, followed by TX AK DONE PRESS ENT.
h. Press [ENT] to return to the rekey/NCD operations menu.
i. Go back to CT operation.
j. Turn off DTD or NCD and disconnect it from the FILL connector.
k. Conduct a communications check to determine if receiving station has received and stored the new TEK.
l. If OTAR was successful, update KEK in NCD using the procedure described in Paragraph 3.22.5.
3.22.1.2 TX AK for KG-84
The radios only need to have the same key. Perform the following procedure for TX AK:
a. Connect Data Transmission Equipment (DTE) device to DATA PORT (J3).
b. Determine TEK that is to be transmitted by AK OTAR. Load this TEK into the AN/PRC-150(C) to have available for communications checks with receiving stations of the OTAR.
c. Notify receiving stations to prepare for AK OTAR. Direct them to use cooperative or noncooperative method. Refer to Paragraph 3.22.1.3.1 and Paragraph 3.22.1.3.2. Verify the CRYPTO TYPE is KG-84. Additionally, instruct them not to transmit again until they hear a communications check. If using cooperative method, tell receiving station to receive new key and store in an unused storage position.
d. Rotate the function switch to RV.
e. Select TRANSMIT AK; press [ENT]. WAIT - CONFIGURING FOR TX AK displays.
f. On the fill device, select AK, the TEK to be transmitted, and the KEK used by the receiving stations.
Consult NCD or DTD operations manual if necessary.
g. When START TX, CONNECT NCD, AND INITIATE AK displays, initiate transmission of data traffic from external DTE device.
NOTE
Do not attempt to use the handset PTT for this action as the results may be unreliable. Keying should be done by asserting an RTS on the radio’s DATA PORT (J3).
NOTE
Do not remove RTS until TX AK DONE STOP TX is displayed.
h. Connect KYX-15 (NCD) or AN/CYZ-10 (DTD) fill device to J18 FILL connector.
i. Initiate the AK from the fill device. On the KDU, TX AK IN PROGRESS displays, then TX AK DONE STOP TX, followed by TX AK DONE PRESS ENT.
NOTE
Transmission of data will continue for several seconds after DTE RTS is removed. Remain in RV until TX AK DONE PRESS ENT is displayed.
j. Press [ENT] to return to the rekey/NCD operations menu.
k. Go back to CT operation.
l. Turn off DTD or NCD and disconnect it from the FILL connector.
m. Conduct a communications check to determine if receiving station has received and stored the new TEK.
n. If OTAR was successful, update KEK in NCD using the procedure described in Paragraph 3.22.1.3.
3.22.1.3 Receive Automatic Rekey (RX AK)
The AN/PRC-150(C) supports cooperative and noncooperative RX AK. AK rekeying requires receiving radio to have the same KEK as being used by transmitting NCD or DTD stations. Use cooperative method to send TEKs to outstations as a routine update to already established nets, or to add capability to operate in additional nets.
NOTE
It is not recommended to use noncooperative OTAR as a method to update COMSEC in multiple station nets as the possibility of having some stations not receive the update will result in the net being mixed with stations using two different keys. Use of noncooperative OTAR methods should be limited to stations with untrained operators and as a means of corrective action for stations not able to change keys at end of scheduled crypto periods.
3.22.1.3.1 Cooperative RX AK OTAR
The AK OTAR process requires that the receiving AN/PRC-150(C) have the same KEK and is using the same COMSEC type that the sending station is using.
Perform the following procedure for cooperative RX AK OTAR:
a. Upon receiving notification that NCS will transmit an AK OTAR, acknowledge instructions and do not transmit again until the procedure has completed and the NCS makes another communications check.
b. Rotate function switch to RV.
c. Select RECEIVE AK; press [ENT]. WAIT - CONFIGURING FOR RX AK displays followed by WAIT TO RECEIVE AK.
d. Wait for sending station to transmit AK OTAR. RX AK IN PROGRESS displays, followed by RX AK OK.
e. Select the desired TEK location (01 - 25). Use an unused storage position or you will lose your current key which may still be needed. KEY STORE IN PROGRESS displays, followed by KEY STORE OK, if successful. If unsuccessful, coordinate with the sending station to repeat the process.
f. If the KEK is updated during the RX AK, the KEK update count displays.
g. Go back to CT operation. Wait for communications check from NCS. Acknowledge to NCS if process was successful and if KEK update was indicated.
3.22.1.3.2 Noncooperative RX AK
The AK OTAR process requires that the receiving AN/PRC-150(C) have the same KEK and is using the same COMSEC type that the sending station is using. Perform the following procedure for noncooperative RX AK:
a. Upon notification from the NCS that an AK OTAR is to be transmitted, acknowledge instructions. Do not transmit again until the process is complete and the NCS makes a communications check.
b. Wait to receive the AK.
NOTE
If the preset screen is visible, the encryption key field will blink during the key transfer process.
c. If the AK is received successfully, the new key overwrites the selected TEK.
d. Wait for communications check from the sending station. The sending station will make the first check on the new TEK. If the OTAR process was unsuccessful, the communications check will be made on the old key and the process will need to be reattempted.