Cryptographic processor (CRYP) RM0090
734/1731 DocID018909 Rev 11
Figure 230. Initialization vectors use in the TDES-CBC encryption
23.3.5 CRYP busy state
When there is enough data in the input FIFO (at least 2 words for the DES or TDES
algorithm mode, 4 words for the AES algorithm mode) and enough free-space in the output
FIFO (at least 2 (DES/TDES) or 4 (AES) word locations), and when the bit CRYPEN = 1 in
the CRYP_CR register, then the cryptographic processor automatically starts an encryption
or decryption process (according to the value of the ALGODIR bit in the CRYP_CR
register).
This process takes 48 AHB2 clock cycles for the Triple-DES algorithm, 16 AHB2 clock
cycles for the simple DES algorithm, and 14, 16 or 18 AHB2 clock cycles for the AES with
key lengths of 128, 192 or 256 bits, respectively. During the whole process, the BUSY bit in
the CRYP_SR register is set to ‘1’. At the end of the process, two (DES/TDES) or four (AES)
words are written by the CRYP Core into the output FIFO, and the BUSY bit is cleared. In
#290?)6,
BITSTRING
-----
4$%3#"# ENCRYPTION EXAMPLE $!4!490% B
-----
BIT
BITBITBITBIT
BITBITBITBITBIT
FIRSTWORDWRITTENINTOTHE#290?$).REGISTER
SECONDWORDWRITTENINTOTHE#290?$).REGISTER
)6
#290?)62
$%!%NCRYPT +
$%!$ECRYPT +
$%!%NCRYPT +
#290?)6, #290?)62
#290RESULTISCOPIED
BACKTOTHE#290?)6,2
REGISTERSAFTERCYPHERING
/54&)&/
&IRSTWORDFROMTHE/54&)&/CONTAINSTHELEFTPARTOFTHECYPHERTEXTBLOCK/
3ECONDWORDFROM/54&)&/CONTAINSTHERIGHTPARTOFCYPHERTEXTBLOCK/
)6 )6 )6 )6 )6 )6 )6 )6 )6
)
) ) ) ) ) ) )) )
)6
)6 )6 )6 )6 )6 )6 )6 )6 )6
AI
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