AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 22

• Manufacturer Part Number: AT88SC0104CA_11
• Description: Atmel CryptoMemory Specification Datasheet
• Manufacturer: ATMEL [ATMEL Corporation]

6.3.13 Session Keys (S
6.3.14 Secret Seeds (G
6.3.15 Password Sets
6.3.16 Secure Code
6.3.17 Password Attempts Counters (PAC)
6.3.18 Authentication Attempts Counters (AAC)
6.4
Each of these fields contains a 64-bit session key for use during encryption. The internal logic modifies the session key each
time it successfully processes authentication or encryption verification. The session keys do not require initial values and does
programming initial values are not necessary.
Each of these fields contains a 64-bit secret seed that is used in conjunction with the corresponding cryptogram and session
key during the authentication and encryption sequences. The customer programs the secret seeds during device
personalization.
The password fields contain eight sets of two 24-bit passwords for read and write operations. The customer defines the values
of these passwords during personalization. Successfully verifying the write password allows modification of the read and the
write passwords of the same set.
The secure code is the Write 7 password. Properly presenting this password grants write access to the configuration memory
during personalization. Atmel defines the initial value of the secure code but the customer may change these values after
successful presentation during a verify password operation for Write 7 password.
shows the secure codes for various devices when they leave the Atmel factory. After blowing the PER fuse, verifying Write 7
password no longer grants write access to the configuration memory, and the configuration memory becomes read-only
thereafter.
Each of the sixteen PAC fields contains an 8-bit attempts counter for the verify password process. Each PAC corresponds to a
password. The attempts counter limits the number of incorrect consecutive presentations of the corresponding password to
four, after which it locks the password from future use. The PAC will decrement ($FF, $EE, $CC, $88, $00) with each incorrect
attempt to present the password. The PAC permanently locks the corresponding password once its value reaches $00. Prior
to reaching $00, any correct presentation of the password resets the PAC value to $FF.
Each of the four AAC fields contains an 8-bit attempt counter for the authentication process. Each AAC field corresponds to
each authentication key set. The attempts counter limits the number of incorrect consecutive attempts to authenticate to for,
after which it locks the authentication key set from future use. The AAC will decrement ($FF, $EE, $CC, $88, $00) with each
incorrect attempt to authenticate. The AAC permanently locks the corresponding key set once its value reaches $00. Prior to
reaching $00, any correct attempt to authenticate resets the AAC value to $FF.
Security Fuses
CryptoMemory uses four fuses. The status of these fuses is given in a ‘fuse byte.’ A value of ‘0’ indicates that the fuse has
been blown. Bits four to seven of this byte are not used as security fuses and are reserved for Atmel use.
Table 6-9.
resv
F
7
Device Fuses
0
0
-G
– S
resv
F
3
6
)
3
)
resv
F
5
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
resv
F
4
SEC
F
3
Table 6-3, Factory Programmed Fields
PER
F
2
CMA
8664E−CRYPTO−12/11
F
1
FAB
F
0
22