at88sa102s ATMEL Corporation, at88sa102s Datasheet - Page 3

• Manufacturer Part Number: at88sa102s
• Description: Cryptoauthentication
• Manufacturer: ATMEL Corporation

8584A–SMEM–03/09
Table 1.
BurnSecure Enable
BurnFuse Enable
Secret Fuses
Status Fuses
Fuse Disable
0
1
2
64
87
88
96
Fuse #
63
86
95
127
The 128 fuses in the AT88SA102S chip are arranged in the following manner:
BurnSecure Enable
BurnFuse Enable
Secret Fuses
Status Fuses
Fuse Disable
MfrID
Serial Number
1.
2.
Name
This fuse is used to prevent repetitive operation of the two personalization commands:
GenPersonalizationKey and BurnSecure. This fuse is always burned by the BurnSecure
command.
This fuse is used to prevent operation of the BurnFuse command in the application. This
fuse must be burned using the BurnSecure command.
These 62 fuses are used to augment the keys stored elsewhere in the chip. Knowledge of
both the internally stored keys and the values of the Secret Fuses is required to generate
the correct response to the Cryptographic command of the AT88SA102S. An arbitrary
selection of these fuses is burned during personalization via the execution of a single
BurnSecure command.
The chip includes security mechanisms designed to prevent an observer on the bus from
determining which fuses have been burned. In addition, the personalization process can be
run only once to prevent various field attacks on the secret fuse value.
Within this document, “Secret Fuses” is used to refer to the entire array of 64 bits: Fuse[0-
63], even though the values of Fuse[0] and Fuse[1] are fixed for most applications and their
value can be derived from the operation of the chip.
These 23 fuses can be used to store information which is not secret, as their value can
always be determined using the Read command. They can be written at the same time as
the secret fuses using the BurnSecure command, or they can be individually burned at a
later time with the BurnFuse command. Two common usage models for these fuses are:
Calibration or model number information. In this situation, the 23 bits are written at the
factory. This method can also be used for feature enabling. In this case, the BurnFuse
command should not be run in the field, and the BurnFuse Enable bit should be a 0.
Consumption logging, i.e. burn one bit after every n uses, the host system keeps track of the
number of uses so far for this serial number. In this case, the BurnFuse command is
necessary to individually burn one of these 23 bits, and the BurnFuse Enable bit should be
a 1.
Within this document, “Status Fuses” is used to refer to the entire array of 24 bits: Fuse[64-
87], even though the value of Fuse[87] is fixed after personalization and cannot be modified
in the field.
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.
If this fuse is a 1, then the BurnSecure command is enabled. If this fuse is
burned, then the BurnSecure command is disabled.
If this fuse is a 1, then the BurnFuse command is enabled. If it is burned, then
the BurnFuse command is disabled.
These fuses can be securely written by the BurnSecure command but can
never be read directly with the Read command.
These fuses can be written with the BurnSecure command and can always be
read with the Read command.
The MAC command ignores the values of Fuse[0-86] until this bit is burned.
See Section 1.2. Set by Atmel, can’t be modified in the field.
See Section 1.2. Set by Atmel, can’t be modified in the field.
AT88SA102S [Preliminary]
Description
3