at88sc018 ATMEL Corporation, at88sc018 Datasheet - Page 10

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

1.5.4. Passwords
1.5.5. Nonvolatile Counters
1.5.6. RNGSeed
1.5.7. Read Only Memory
10
P0-P15. These are the passwords used to enable reading and/or writing of various zones in CRF. For example, CP0 is
the configuration byte for P0, and determines the particular attributes which govern the use of P0. The password
configuration bytes are organized as below:
Table 10.
Once the AT88SC018 is locked, these elements (P0-P15 & CP0-CP15) can never be read directly, nor can they be
written.
The AT88SC018 implements 4 counters that can each increment to a maximum value of 6.4 million. They cannot be
reset, nor can they be decremented. Their current state can be read using the ReadCounter command and they are
incremented with the IncrementCounter command. It is recommended that the IncrementCounter command not be
issued after the counter has reached a value of 6.4 million.
authorization to have completed.
The above constraints only apply to a locked CMC. In an unlocked AT88SC018, the contents of the EEPROM locations
that hold the current state of the various counters can be freely read and/or written using ReadMemory
(ReadMemoryDigest) or WriteMemory (WriteMemoryEncrypted).
They should be initialized to a count of 0 before the AT88SC018 is locked, by writing the following values into all four of
the 16 byte counter areas: “0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0x00 0x00 0x00 0x00 0xFF 0x00 0x00 0x00”
at addresses “x0, x1, …”. Atmel recommends that all counters be properly initialized even if the application does not
utilize all of them.
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 as part of the input to the random number
generation capability 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.
When the part is locked, the memory in this area can be read but never written except as described in the next
paragraph. After the system has properly responded to the startup challenge, there are no restrictions on the reading of
this memory. This memory section starts at address 0x110 and extends to 0x100 | RW-Bound – 1.
RW-Bound must be at least 0x10 and less than 0xF8 or F-Bound, whichever is smaller.
CryptoCompanion Chip
0
1
2 – 3
4 – 7
Bit #
Encrypt
Connect
Reserved
F Number
Password Configuration Bits.
Name
If 1, EncryptPassword will return this password value in the clear. In this situation, the
password offers little security value but may be useful for mapping.
If 1, then obey the “F number” restrictions below. If 0, ignore “F Number”.
Must be 0.
The secret to which this password is connected. Unless the current authentication session
has been computed using this secret this password cannot be read in either clear or
encrypted mode.
Access to these two commands does not require
Description
5277C–CryptoCompanion–9/09