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Name
A0
Byte
0
1
2
Name
Flag
Name
FLAG-A0
Bit
7
Name
Reserved
Value
0
8. The software loads A0 by selecting a Load IV/nonce command. To do so, it sets the mode to CFB or
OFB at the same time it selects the Load IV/nonce command.
9. The software calls a CFB or an OFB encryption on the authenticated data T. The uploaded buffer
contents stay unchanged (M = 16), or only its first M bytes stay unchanged, the others being set to 0
(M – 16). The result is U, which is used later.
10. The software calls a CTR-mode encryption immediately on the still-padded message blocks. It must
reload the IV when the CTR value is any value but zero.
11. The encrypted authentication data U is appended to the encrypted message. This gives the final
result, C.
Result C = encrypted message(m) + U
SWRU191F – April 2009 – Revised April 2014
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Designation
First CTR Value for CCM Mode
3
4
5
6
7
Nonce
Figure 15-3. Message Encryption Phase Block
Designation
Encryption Flag Field for CCM Mode
6
5
0
0
Figure 15-4. Encryption Flag Byte
Copyright © 2009–2014, Texas Instruments Incorporated
8
9
10
4
3
—
0
0
CCM Mode
11
12
13
14
CTR
2
1
L – 1
1
0
AES Coprocessor
15
0
1
149
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