ATSHA204 ATMEL [ATMEL Corporation], ATSHA204 Datasheet - Page 44

• Manufacturer Part Number: ATSHA204
• Description: Atmel CryptoAuthentication
• Manufacturer: ATMEL [ATMEL Corporation]

See the NIST HMAC specification for a complete description of how the various digests are calculated using SHA-256, the
HMAC key, and appropriate padding. See http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf. The padding is part of the
SHA-256 message (see Section 3.1). HMAC is a construct that sits on top of SHA-256.
Table 8-19. Mode Encoding
Bits
0-1
7
6
5
4
3
2
Meaning
Must be zero.
If set, include the 48 bits SN[2:3] and SN[4:7] in the message.
Otherwise, the corresponding message bits are set to zero.
Include the first 64 OTP bits (OTP[0] through OTP[7]) in the message.
Otherwise, the corresponding message bits are set to zero.
If Mode[4] is set, the value of this mode bit is ignored.
Include the first 88 OTP bits (OTP[0] through OTP[10]) in the message.
Otherwise, the corresponding message bits are set to zero.
Must be zero.
The value of this bit must match the value in TempKey.SourceFlag or the command will return an error.
Must be zero.
Atmel ATSHA204 [DATASHEET]
8740D−CRYPTO−3/12
44