ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
Name
Size Notes
Bit 0:
0: Slot<SlotID>
1: TempKey
Source of the second 32-bytes of the SHA message.
0: ClientChal parameter
1: TempKey
Param2 SlotID
2 Which internal slot is to be used to generate the response. Only bits 3-0 are used.
Data1 ClientChal 32 Challenge sent to Client. (Must appear in the input stream).
Data2 ClientResp 32 Response generated by the Client.
Data3 OtherData 13 Remaining constant data needed for response calculation.
Table 8-9. Output parameter
Name Size Notes
Result
1
Returns a 1-byte value of zero if ClientResp matches the internally computed digest, one if there is a
mismatch.
The message that is hashed with the SHA-256 algorithm consists of the following information:
32 bytes
32 bytes
4 bytes
8 bytes
3 bytes
1 byte
4 bytes
2 bytes
2 bytes
key<SlotID> or TempKey (depending on the mode)
ClientChal or TempKey (depending on the mode)
OtherData<0:3>
OTP<0:7> or zeros (depending on the mode)
OtherData<4:6>
SN<8>
OtherData<7:10>
SN<0:1>
OtherData<11:12>
The purpose of OtherData is to construct a SHA-256 message that matches identically to the MAC
message that was used to produce ClientResp. By comparing the message used for the SHA-256 of the
MAC command, OtherData is parsed as follows:
Table 8-10. OtherData
Size CheckMac
1 OtherData<0>
1 OtherData<1>
2 OtherData<2:3>
3 OtherData<4:6>
4 OtherData<7:10>
2 OtherData<11:12>
MAC
OpCode
Mode
SlotID
OTP<8:10>
SN<4:7>
SN<2:3>
Notes
MAC OpCode = 0x08
Mode used for MAC command.
SlotID used for MAC command.
OTP<8:10> used for MAC command. (Useful for Legacy.)
SN<4:7> used for MAC command. (Unique per Client.)
SN<2:3> used for MAC command. (Unique per Client.)
© 2018 Microchip Technology Inc.
DS40002025A-page 48
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