AT88SA100S-SH-CZ-T ATMEL [ATMEL Corporation], AT88SA100S-SH-CZ-T Datasheet - Page 4

• Manufacturer Part Number: AT88SA100S-SH-CZ-T
• Description: Atmel CryptoAuthentication Battery Authentication Chip
• Manufacturer: ATMEL [ATMEL Corporation]

1.4
1.4.1
1.5
SHA-256 Computation
This chip performs only one cryptographic calculation – a keyed digest of an input challenge using the SHA-256 algorithm,
documented here:
http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf
SHA Computation Example
In order to ensure that there is no ambiguity, the following example vector is provided in addition to the sample vectors in the
NIST document. In this example, all values are listed in hex. For all but the key, bytes are listed in the order that they appear
on the bus – first on the left. Key is listed in the same order, so the 01 at the left of the key string is the first byte passed to
SHA-256.
SHA Computation Example
A read command executed on Address 0 of the ROM (ROM MfrID, ROM SN) would return CC DD EE FF, with CC being the
first byte on the bus and FF being the last.
Throughout this document, the complete message processed by the SA100S chip is documented. According to the above
specification, this always includes a single bit of ‘1’ pad after the message, followed by a 64-bit value representing the total
number of bits being hashed (less pad and length). If the length is less than 447 (512-64-1) then the necessary number of ‘0’
bits are included between the ‘1’ pad and ‘length’ to stretch the last message block out to 512-bits.
When using standard libraries to calculate the SHA-256 digest, these pad and length bits should probably not be passed to the
library as most standard software implementations of the algorithm add them in automatically.
Security Features
The AT88SA100S incorporates a number of physical security features designed to protect the key from unauthorized release.
These include an active shield over the entire surface of the internal memory encryption, internal clock generation, glitch
protection, voltage tamper detection and other physical design features.
Both the clock and logic supply voltage are internally generated, preventing any direct attack via the pins on these two signals.
Key
Challenge
Opcode
Mode
Param2
Fuse MfrID
Fuse S/N
ROM MfrID CCDD
ROM SN
The 88-bytes over which the digest is calculated are:
Digest:
01030507090B0D0F11131517191B1D1F21232527292B2D2F31333537393B3D3F
020406080A0C0E10121416181A1C1E20222426282A2C2E30323436383A3C3E40
08
40 (include serial number in message)
0000
77
8899AABB
EEFF
0103…3D3F0204…3E4001400000…EEFF
7D38245733717A488575B9F794F7BCAFE033A3848D39430DA25141FDEBEAA1C2
Atmel AT88SA100S [DATASHEET]
8558F−CRYPTO−9/11
4