1 dynamically assigned aesu, Dynamically assigned aesu -84 – Freescale Semiconductor MCF5480 User Manual
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MCF548x Reference Manual, Rev. 3
22-84
Freescale Semiconductor
22.14.5.1 Dynamically Assigned AESU
shows a descriptor for a dynamically assigned AESU. The descriptor loads a key into the
AESU, performs the cipher on data, and writes the result and optional context (IV) to memory.
5
FM
Final MAC. Processes final message block and generates final MAC tag at end of message
processing (OCB and CCM mode only)
0 Do not generate final MAC tag
1 Generate final MAC tag after CCM processing is complete.
4
IM
Initialize MAC. Initializes AESU for new message (CCM mode only)
0 Do not initialize (context will be loaded by host)
1 Initialize new message with nonce
3
—
Reserved, should be cleared.
2–1
CM
Cipher Mode. Controls which cipher mode the AESU will use in processing:
00 ECB -Electronic Codebook mode.
01 CBC- Cipher Block Chaining mode.
10 Reserved
11 CTR- Counter Mode.
Note: CM must be set to 00 when Extend Cipher Mode (Bit 0) is set, otherwise an error will be
generated.
0
ED
Encrypt/Decrypt. If set, AESU operates the encryption algorithm; if not set, AESU operates the
decryption algorithm.
Note: This bit is ignored if CM is set to “11” - CTR Mode.
0 Perform decryption
1 Perform encryption
Table 22-77. Descriptor for a Dynamically Assigned AESU
Field Name
Value/Type
Description
Header
Header common to several descriptors (TYPE 0001)
LEN_1
Length (not used)
NULL
PTR_1
Pointer (not used)
NULL
LEN_2
IV Length
Number of bytes in input IV (56 bytes) (optional)
PTR_2
IV Pointer
Address of input IV (optional)
LEN_3
Key Length
Number of bytes in Key (16, 24, or 32 bytes)
PTR_3
Key Pointer
Address of Key
LEN_4
Data In Length
Number of bytes of data to be ciphered (multiple of 16)
PTR_4
Data In Pointer
Address of data to be ciphered
LEN_5
Data Out Length
Bytes of output data (should be equal to length of data in)
PTR_5
Data Out Pointer
Address to write output data
LEN_6
IV Out Length
Number of bytes of output IV to be written (56 bytes) (optional)
Table 22-76. AESU Mode Register Field Descriptions (Continued)
Bits
Name
Description