AT88SA102S-TH-T Atmel, AT88SA102S-TH-T Datasheet - Page 4

• Manufacturer Part Number: AT88SA102S-TH-T
• Manufacturer: Atmel

Specifications of AT88SA102S-TH-T

• Lead Free Status / RoHS Status: Supplier Unconfirmed

1.4.
1.5.
1.6.
4
Fuse Disable
Chip Identification
The chip includes a total of 72 bits of information that can be used to distinguish between individual chips in a reliable
manner. The information is distributed between the ROM and fuse blocks in the following manner.
Serial Number
Manufacturing ID This 24 bit value is composed of ROM MfrID (16 bits) and Fuse MfrID (8 bits). Typically this value
Key Values
The values stored in the AT88SA102S internal key array are hardwired into the masking layers of the chip during wafer
manufacture. All chips have the same keys stored internally, though the value of a particular key cannot be determined
externally from the chip. For this reason, customers should ensure that they program a unique (and secret) number into
the 64 secret fuses and they should store the Atmel provided key values securely.
Individual key values are made available to qualified customers upon request to Atmel and are always transmitted in a
secure manner.
When the serial number is included in the MAC calculation then the response is considered to be diversified and the
host needs to know the base secret in order to be able to verify the authenticity of the client. A diversified response can
also be obtained by including the serial number in the computation of the value written to the secret fuses. An Atmel
CryptoAuthentication host chip provides a secure hardware mechanism to validate responses to determine if they are
authentic.
SHA-256 Computation
CryptoAuthentication performs only one cryptographic calculation – a keyed digest of an input challenge. It optionally
includes various other information stored on the chip within the digested message.
CryptoAuthentication computes the SHA-256 digest based on the algorithm documented here:
http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf
Throughout this document, the complete message processed by the AT88SA102S 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.
AT88SA102S
This 48 bit value is composed of ROM SN (16 bits) and Fuse SN (32 bits). Together they form a
serial number that is guaranteed to be unique for all devices ever manufactured
CryptoAuthentication family. This value is optionally included in the MAC calculation.
is the same for all chips of a given type. It is always included in the cryptographic computations.
This fuse is used to disable/enable the ability of the MAC command to read the fuse values
until the BurnSecure command has completed properly. When it has a value of 1
(unburned), the bit values in the message that would normally have been filled in with Fuse
values are all set to a 1. When FuseDisable is burned, the MAC command fills in the
message with the requested fuse values. Additionally, this bit, when burned, disables the
BurnSecure command to prevent modification of the secret fuses and BurnFuse enable bit
in the end customer application.
8584D–SMEM–5/10
within the