SEC Lite Descriptors
MPC885 PowerQUICC Family Reference Manual, Rev. 2
49-8
Freescale Semiconductor
knowledge of the security association of the previous or next packet. This situation calls for the use of
dynamic descriptors.
When under dynamic assignment, an EU must be used under the assumption that a different
crypto-channel (with a different context) may have just used the EU and that another crypto-channel (with
yet another context) may use that EU immediately after the current crypto-channel has released the EU.
Therefore, for dynamic-assignment use, which is the only option for the SEC Lite, there is a set of data
packet descriptors defined that sets up the appropriate context, performs the cipher function, and then
saves the context to system memory.
The descriptor shown in
Table 49-8
completely sets up the DEU and MDEU for an encryption operation;
loads the HMAC and symmetric keys, context, and data; writes the permuted data back to memory; and
writes the HMAC and any altered context (IV) back to memory. (This may be necessary when DES is
operating in CBC mode with implicit IV.) Upon completion of the descriptor, the DEU and MDEU is
cleared and released.
Table 49-8. Descriptor_HMAC_Snoop_Non_AFEU
Field
Value / Type
Description
HMAC_Snoop_Non_AFEU
0x2073_FC20
Typical IPSec descriptor. With 3DES-HMAC-SHA-1
LEN_1
Length
Number of bytes of HMAC key to be written
PTR_1
Pointer
Pointer to HMAC key
LEN_2
Length
Number of bytes data to be processed for HMAC
PTR_2
Pointer
Pointer to start of HMAC data
LEN_3
Length
Number of bytes of symmetric key
PTR_3
Pointer
Pointer to symmetric key
LEN_4
Length
Number of bytes of symmetric IV
PTR_4
Pointer
Pointer to symmetric IV
LEN_5
Length
Length of data to be read and permuted
PTR_5
Pointer
Pointer to data in memory
LEN_6
Length
Length of data to be written after permutation
PTR_6
Pointer
Pointer to memory buffer for write back
LEN_7
Length
Length of HMAC to be written to memory
PTR_7
Pointer
Pointer to memory buffer for HMAC
PTR_NEXT
Pointer
Pointer to Next Descriptor
Summary of Contents for PowerQUICC MPC870
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