Freescale Semiconductor MCF5480 - Manual (Page 692)

MCF548x Reference Manual, Rev. 3
22-90 Freescale Semiconductor
Table 22-89 shows the format used for the context input for AES-CCM.
Table 22-87 shows the format used for the context output for AES-CCM.
22.14.6 Multi-Function Data Packet Descriptors
The SEC supports a limited subset of multi-function descriptors. In particular, the SEC supports chaining
either DEU, AESU, or AFEU compatible outputs to the MDEU input. Further, the SEC can be configured
LEN_6 IV Out Length Number of bytes of output IV to be written (24 or 32 bytes)
PTR_6 IV Out Pointer Address where output IV is to be written
LEN_7 MAC Out Length NULL
PTR_7 MAC Out Pointer NULL
PTR_NEXT Next Descriptor Pointer Pointer to next data packet descriptor
Table 22-89. AES-CCM Decryption Context Input Format
Offset from
Input Context
Base Address
Field Length Description
0x0 IV 16 bytes This is the session specific IV parameter
0x10 Encrypted MAC 8 bytes These 8 bytes are loaded with the encrypted MAC
from the inbound frame.
0x18 Encrypted MAC
(cont.) 8 bytes These 8 bytes can be used for the continuation of the
encrypted MAC if it is larger than 8 bytes. Otherwise
this field should be filled with zeroes.
0x20 Counter 16 bytes The counter is a second session specific parameter
similar to the IV.
0x30 Counter
modulus 8 bytes Always 8 for 802.11, but can very in other protocols.
Table 22-90. AES-CCM Decryption Context Output Format
Offset from
Output Context
Base Address
Field Length Description
0x0 MAC Tag 8 bytes The MAC Tag is compared to the decrypted MAC
0x8 MAC Tag (cont.) 16 bytes Continuation of the MAC Tag if it is larger than 8 bytes.
Typically this field will be all zeroes.
0x10 Decrypted MAC 8 bytes Compared to the MAC tag to determine if the frame
passes its integrity check.
0x18 Decrypted MAC
(cont.) 8 bytes If the MAC is larger than 16 bytes, this is the
continuation of the decrypted MAC.
Table 22-88. Descriptor for a AES-CCM Decryption (Continued)
Field Name Value/Type Description