CC2430-RTR1-F64Z datasheet(137/234 Pages) TI

137 / 234 page

CC2430

CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A

Page 137 of 232

•

(3a)

If l(a)=0, (that is A_Data =0),

then L(a) is the empty string. We

note l(a) the length of a in octets.

•

(3b)

If 0 < l(a) < 2

16 - 28 , then L(a)

is the 2-octets encoding of l(a).

The Additional Authentication Data is

appended to the A_Data length field L(a).

The Additional Authentication Blocks is

padded with zeros until the last Additional

Authentication Block is full. There is no

restriction on the length of a.

AUTH-DATA = L(a) + Authentication Data

+ (zero padding)

(4) The last block of the message is

padded with zeros until full (that is if its

length is not a multiple of 128).

(5)

The software concatenates the block

B0, the Additional Authentication Blocks if

any, and the message;

Input message = B0 + AUTH-DATA +

Message + (zero padding of message)

(6)

Once the input message authentication

by CBC-MAC is finished, the software

leaves the uploaded buffer contents

unchanged (M=16), or keeps only the

buffer’s higher M bytes unchanged, while

setting the lower bits to 0 (M != 16).

The result is called T.

Message Encryption

(7)

The software creates the key stream

block A0. Note that L=6, with the current

example of the CTR generation. The

content is shown in Figure 30.

Note that any value but zero works for the

CTR value.

The content of the Encryption Flag byte is

described in Figure 31.

Name

Designation

First CTR value for CCM mode

Byte

Name

Flag

NONCE

CTR

Figure 30: Message Encryption Phase Block 0

Name

FLAG/A0

Designation

Encryption Flag Field for CCM mode

Bit

Name

Reserved

L-1

Value

Figure 31: Encryption Flag Byte

Message Encryption (cont.)

(8) The software loads A0 by selecting a

Load IV/Nonce command. To do so, it sets

Mode to CFB or OFB at the same time it

selects the Load IV/Nonce command.

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