at88sc018 ATMEL Corporation, at88sc018 Datasheet - Page 11

• Manufacturer Part Number: at88sc018
• Description: Cryptocompanion? Chip For Cryptomemory And Cryptorf
• Manufacturer: ATMEL Corporation

1.5.8. Read / Write Memory
1.5.9. Secrets
1.5.10. CF0 – CF15
1.5.11. Restricted Bytes
5277C–CryptoCompanion–9/09
The memory in this area has general read/write permissions, similar to a standard serial EEPROM. After the system
has properly responded to the startup challenge, there are no restrictions on the access to this memory.
The first byte in this section is at address 0x100 | RW-Bound. If RW-Bound is less than 0x10 the results will be
unpredictable.
F0-F15. These secrets are used to generate the G
SHA-1. Up to 16 F values that can be supported by the AT88SC018.
The low byte of the memory address of the first should be written into F-Bound. The 3 least significant bits of F-bound
are ignored. The first F value is always F0, independent of F-Bound. If F-bound is < RW-Bound or if F-Bound is < 0x80,
the results will be unpredictable.
Example
If F-Bound is 0xD0, the first F value is F0 at memory address 0x1D0. The last F value is F5 at address 0x1F8.
Example
If 0xFF is written into F-Bound, CMC will use only a single secret, named F0, which will be located at address 0x1F8
(since the low three bits of F-bound are ignored).
These elements can never be read directly, nor can they be written after the part has been locked.
This location within the EEPROM is initialized during Atmel manufacturing with a 16 byte random number obtained
from an external high quality hardware random number generator. It is used internally within the AT88SC018. It may be
read and/or written when the part is unlocked. Atmel does not recommend that it be written to a fixed value.
These locations within the EEPROM are initialized during Atmel manufacturing with a 4 byte random number obtained
from an external high quality hardware random number generator. It is used internally within the AT88SC018. It cannot
be read and/or written when the part is unlocked or locked. When reading from these locations, the result will be 0xFF
for these 4 bytes.
C
value for the particular CM/CRF chip based on the F1 algorithm,
CryptoCompanion Chip
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