at88rf04c ATMEL Corporation, at88rf04c Datasheet - Page 5

• Manufacturer Part Number: at88rf04c
• Description: 13.56 Mhz Cryptorf Eeprom Memory 4 Kbits
• Manufacturer: ATMEL Corporation

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10.
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11.1.
8672AS–CRRF–04/09
Security Methodology
Figure 3.
Memory Access
Depending on the device configuration, the host will carry out the authentication protocol and/or present different
passwords for each operation: read or write. To insure security between the different user zones, each zone can use a
different set of passwords or keys. A specific attempts counter for each password and for each authentication key
provides protection against systematic attacks.
Security Operations
Anti-tearing
In the event of a power loss during a write cycle, the integrity of the device’s stored data may be recovered. This
function is optional: the host may choose to activate the anti-tearing function depending on application requirements.
When anti-tearing is active, write commands take longer to execute since more write cycles are required to complete
them. Data writes are limited to 8-byte pages when anti-tearing is active.
Data is written first to a buffer zone in EEPROM instead of to the intended destination address, but with the same
access conditions. The data is then written to the required location. If this second write cycle is interrupted due to a
power loss, the device will automatically recover the data from the buffer zone at the next power-up.
Check Password (WPW)
Check Password (RPW)
Device (card)
Compute Challenge B
Security Methodology
Checksum (CS)
Card Number
Challenge B
VERIFY CS
Write DATA
VERIFY A
DATA
COMPUTE Challenge A
Challenge A
VERIFY B
Read Password (RPW)
VERIFY CS (optional)
Write Password (WPW)
DATA
CS
Host (reader)
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