ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
Data
Name Size Notes
Param2<3:0> only are used to select a slot but all 16 bits are used in the HMAC message.
—
0—
Table 8-18. Ouput Parameter
Name
Response
Size
32
Notes
HMAC digest
The HMAC digest is computed using the key at SlotID as the HMAC key over a message consisting of
the following information:
32 bytes
32 bytes
1 byte
1 byte
2 bytes
8 bytes
3 bytes
1 byte
4 bytes
2 bytes
2 bytes
Zeros
TempKey
Opcode (always 0x11)
Mode
SlotID
OTP<0:7> or zeros (See table below)
OTP<8:10> or zeros (See table below)
SN<8>
SN<4:7> or zeros (See table below)
SN<0:1>
SN<2:3> or zeros (See table below)
See Section HMAC/SHA-256 for the governing documents which contain a complete description of how
the various digests are calculated using SHA-256, the HMAC key and appropriate padding.
Table 8-19. Mode Encoding
Bits Meaning
7 Must be zero.
0 = 48 Bits corresponding to SN<2:3> and SN<4:7> are set to zero.
6
1 = Include the 48 bits SN<2:3> and SN<4:7> in the message
0 = 64 Bits corresponding to OTP<0> through OTP<7> are set to 0.
5
1=
Include the first 64 OTP bits(8 Bytes) OTP<0> through OTP<7> in the message.
If Mode<4> is set, the value of this mode bit is ignored.
0 = 88 Bits (11 Bytes) corresponding to OTP<0> through OTP<10> are set to 0.
4
1 = Include the first 88 OTP bits(11 Bytes) OTP<0> through OTP<10> in the message.
3 Must be zero.
© 2018 Microchip Technology Inc.
DS40002025A-page 54
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