CC2520_17 Datasheet, PDF (100/134 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
26.9.3 Combination of Encryption and Authentication Using CCM*
This example uses a MAC command frame and demonstrates how to apply both encryption/decryption and
authentication using the CCM/UCCM instructions.
//Write frame data to RAM
//Start at address 0x200
MEMWR(A={02 00} D={2b dc 84 21 43 02 00 00 00 00 48 de ac ff ff 01 00 00 00 00 48 de ac 06 05 00 00
00 01 CE})
//Write key to RAM in reverse byte order
//Start at address 0x230
MEMWR(A={02 30} D={cf ce cd cc cb ca c9 c8 c7 c6 c5 c4 c3 c2 c1 c0})
//Write concatenation of flags, nonce and counter to RAM in reversed byte order
//Starting at address 0x240
MEMWR(A={02 40} D={00 00 06 05 00 00 00 01 00 00 00 00 48 de ac 09})
//Do CCM instruction.
//Replace the last byte in the plaintext frame with the cipehertext and encrypted MIC by setting
the output address E to 0x000.
CCM(P={01} K={23} C={01} N={24} A={200} E={000} F={1d} M={02})
The expected output from the CCM instruction is {D8 4F DE 52 90 61 F9 C6 F1}.
To decrypt the frame in the receiver, the following steps are required. It is assumed that the packed data is
already present in RAM from address 0x200.
//Write key to RAM in reverse byte order
//Start at address 0x230
MEMWR(A={02 30} D={cf ce cd cc cb ca c9 c8 c7 c6 c5 c4 c3 c2 c1 c0})
//Write concatenation of flags, nonce and counter to RAM in reversed byte order
//Starting at address 0x240
MEMWR(A={02 40} D={00 00 06 05 00 00 00 01 00 00 00 00 48 de ac 09})
//Decrypt the frame data and authenticate the MIC. Note that the output address E is set to 0x000.
UCCM(P={01} K={23} C={01} N={24} A={200} E={000} F={1d} M={02})
//Read DPUSTAT register at address 0x02C to check whether the authentication passed or not
REGRD(A={2c})
The expected plaintext output from the UCCM instruction is {CE}.
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